Friday, December 18, 2009
12/18 11:20 AM winter storm update
Band of precip will move into the region within the hour bringing a mix of rain, snow and sleet. The precip could initially fall as rain as the column saturates and cools. This band of precip is associated with the strong 850 mb low... Expect precip rates to continue to increase as this low skirts south of the region. Current RUC sounding show a 0c isothermal layer throughout the column this afternoon. Surface wet bulb is currently at at or slightly below zero in the triangle. Chance of moderate to heavy snow/Sleet during rush hour looks like a real possibility in the triangle.kk
12/18 winter storm update
Just a quick update on the timing of the snow/mix/rain transition. The transition gradient will be very tight. Greensboro/Winston Salem may see all snow with up to a foot of snow possible. Durham will likely see moderate snow transition to zr later tonight, and those just SW of Raleigh will see very little snow at all.
So my forecast for the triangle is difficult, because depending on where you live in the triangle will depend on how much winter weather you see. The NW will see more snow.. and the SE will see less snow. If the High pressure had been stronger and holding steady the whole region would've seen a historic snow storm... But instead it's this:
Friday afternoon: Snow, possibly mixed with light rain. The snow could be moderate at times in the afernoon. High 36
Friday night: Snow changing to sleet and ZR between 7 PM and 9PM and then all rain after 9PM. The snow could be heavy during the evening. Low 30
Saturday: A chance of freezing drizzle/drizzle and flurries. High 35
Possible snow accumulation totals within the triangle this evening:
Chapel Hill: 2-4 inches
Durham: 2-4 inches
Cary: 1-2 inches
Raleigh: 1 inch
SW of Raleigh: < 1inch
The models are all over the place with the Christmas Eve/Christmas storm.... Showing it as an all rain event at this time. But I can't out rule a major winter storm with this system.
So my forecast for the triangle is difficult, because depending on where you live in the triangle will depend on how much winter weather you see. The NW will see more snow.. and the SE will see less snow. If the High pressure had been stronger and holding steady the whole region would've seen a historic snow storm... But instead it's this:
Friday afternoon: Snow, possibly mixed with light rain. The snow could be moderate at times in the afernoon. High 36
Friday night: Snow changing to sleet and ZR between 7 PM and 9PM and then all rain after 9PM. The snow could be heavy during the evening. Low 30
Saturday: A chance of freezing drizzle/drizzle and flurries. High 35
Possible snow accumulation totals within the triangle this evening:
Chapel Hill: 2-4 inches
Durham: 2-4 inches
Cary: 1-2 inches
Raleigh: 1 inch
SW of Raleigh: < 1inch
The models are all over the place with the Christmas Eve/Christmas storm.... Showing it as an all rain event at this time. But I can't out rule a major winter storm with this system.
Thursday, December 17, 2009
12/17 Weekend winter storm update
Not much of an update is really needed, but I did want to mention the chance of moderate to heavy snow potential Friday afternoon until sometime Friday night/early Saturday morning. GFS Bufkit is showing a dry layer at around 850. The GFS may be having a difficult time handling diabatic cooling due to evaporation. Therefore, I believe an isothermal layer may exist during the evening hours. I think it may be a situation in which light precip will fall as rain (less evap cooling) and more heavier precip (more evap cooling) will fall as snow up until a certain point during the night. Significant snowfall during rush hour is not out of the question. The timing may need to be updated tomorrow on the exact timing of the changeover to rain. I believe that any changeover to ZR will be brief due to latent heat release caused by freezing. Temps will be borderline for ZR to begin with so expect the ZR itself to lead to enough of a temp increase to change the precip to rain over night. Also, most of the precip should end early Saturday morning with some light freezing drizzle and flurries possible through the afternoon.
Will need to really look into the Christmas eve storm as well. Could be anything from all rain to mostly snow to a historic ice storm.... stay tuned. Starting to gain some confidence though that someone will say a major Christmas eve/Christmas storm.
New Forecast:
Friday afternoon: Snow, possibly mixed with the light rain. The snow could be moderate to heavy at times in the afernoon. High 36
Friday night: Snow changing to sleet and ZR between 10 PM and 1AM and then all rain after 1. The snow could be heavy during the evening. Low 30
Saturday: A chance of freezing drizzle and flurries. High 35
Will need to really look into the Christmas eve storm as well. Could be anything from all rain to mostly snow to a historic ice storm.... stay tuned. Starting to gain some confidence though that someone will say a major Christmas eve/Christmas storm.
New Forecast:
Friday afternoon: Snow, possibly mixed with the light rain. The snow could be moderate to heavy at times in the afernoon. High 36
Friday night: Snow changing to sleet and ZR between 10 PM and 1AM and then all rain after 1. The snow could be heavy during the evening. Low 30
Saturday: A chance of freezing drizzle and flurries. High 35
Wednesday, December 16, 2009
12/16 - Weekend Winter Storm Forecast for the Triangle:
Synopsis: A low pressure will form along the gulf coast and move northeast off the North Carolina coast this weekend. Cold air will be in place as the low pressure nears the region which will likely bring wintery precip to the triangle. Forecast confidence is very low.
Discussion: A Miller A low will move up the North Carolina coast increasing moisture flux from the Atlantic into the triangle by Friday afternoon. This low will exit the area slowly first bringing in a round of precip due to overrunning warm advection over a fairly strong cold pool at the surface. A 2nd round of precip affiliated with the deformation band will occur later in the weekend. The GFS and ECMWF are in decently good agreement on the general location and timing of the low pressure. I am looking at GFS Bufkit soundings to determine first guess precip type. Forecast confidence is very low due to precip type remaining near the mixed bag region of the nomogram. Diabatic processes could play a large part in the precip type especially Friday afternoon as the precip begins. Also, this is a cold air damming scenario with cold air filtering in between a fairly weak high to the Northwest and a Low to the northeast. NWS RAH mentioned that this storm compares generally well with a storm in 05 in which very little wintery precip fell in the region. With that in mind this is a completely different storm. GFS and every other model for that matter tends to warm temps too much during a CAD event. This fact makes me want to go with an icier/snowier scenario for the triangle as the GFS already predicting a decent amount of ice and snow, especially in the deformation. Climatology however does not support this type of system as a major winter event however, which is why my confidence is so low. On top of that there will be a tight gradient between the rain/mix/snow lines. Also, diabatic processes will turn borderline temps for freezing rain into temps for rain. Right now it's too far out to truly pinpoint the exact location of the low and the strength of the cold air.
But I will forecast what I see as of now... This is likely to change!
Friday afternoon: A 60% chance of snow possibly mixed with rain
Friday night: 70% chance of snow mixing with freezing rain/rain and sleet by 8PM and then changing to all rain/freezing rain/sleet mix.
Saturday: Rain quickly changing over to freezing rain/drizzle before ending.
Discussion: A Miller A low will move up the North Carolina coast increasing moisture flux from the Atlantic into the triangle by Friday afternoon. This low will exit the area slowly first bringing in a round of precip due to overrunning warm advection over a fairly strong cold pool at the surface. A 2nd round of precip affiliated with the deformation band will occur later in the weekend. The GFS and ECMWF are in decently good agreement on the general location and timing of the low pressure. I am looking at GFS Bufkit soundings to determine first guess precip type. Forecast confidence is very low due to precip type remaining near the mixed bag region of the nomogram. Diabatic processes could play a large part in the precip type especially Friday afternoon as the precip begins. Also, this is a cold air damming scenario with cold air filtering in between a fairly weak high to the Northwest and a Low to the northeast. NWS RAH mentioned that this storm compares generally well with a storm in 05 in which very little wintery precip fell in the region. With that in mind this is a completely different storm. GFS and every other model for that matter tends to warm temps too much during a CAD event. This fact makes me want to go with an icier/snowier scenario for the triangle as the GFS already predicting a decent amount of ice and snow, especially in the deformation. Climatology however does not support this type of system as a major winter event however, which is why my confidence is so low. On top of that there will be a tight gradient between the rain/mix/snow lines. Also, diabatic processes will turn borderline temps for freezing rain into temps for rain. Right now it's too far out to truly pinpoint the exact location of the low and the strength of the cold air.
But I will forecast what I see as of now... This is likely to change!
Friday afternoon: A 60% chance of snow possibly mixed with rain
Friday night: 70% chance of snow mixing with freezing rain/rain and sleet by 8PM and then changing to all rain/freezing rain/sleet mix.
Saturday: Rain quickly changing over to freezing rain/drizzle before ending.
Tuesday, November 10, 2009
Evening update
Not much to change. Will go with 4-6 inch storm fall totals for the triangle. Look for a bulls eye of precip well above three inches in the extreme southeast. The upslope regions may see a bit more as well. I don't see much of a break in the precip from beginning to end now due to the quick enhancement of the coastal low. It will almost be an immediate handoff from the 2 quasi seperate features mentioned earlier. Look for the precip to begin to wind down Thursday afternoon. Heaviest precip should be late tonight through tomorrow morning.
We're off to a pretty decent start already.. maybe moreso than the models were predicting so I wouldn't be shocked to see us in the 6+ range when all is said and done.
We're off to a pretty decent start already.. maybe moreso than the models were predicting so I wouldn't be shocked to see us in the 6+ range when all is said and done.
update on upcoming storm:
NAM now coming in even more bullish than the 6z GFS on precip amounts. So far it seems like a good call to go with the GFS yesterday. Despite the fact that this is an unusual storm, am now feeling extremely confident that we will see a historic storm in the triangle. Will post a quick update once the 12z GFS comes in.
November 09 heavy rain event
Potential historic rainfall event beginning this afternoon and lasting through mid week. Upwards of 5-7 inches could around and east of the triangle.
Moderate to heavy rain will begin later this afternoon into this evening as isentropic lift increases. Radar trends show showers already near the region. Expect these showers to increase in coverage and intensity as the right entrance region of an upper jet moves over the triangle region later this afternoon and through the night. The potential exists for one to two inches overnight as this feature moves through. Very slight lull in the heavy and widespread precip looks to occur tomorrow morning however, the rain will reintinsify Wednesday afternoon and through the night. In fact it appears that this has the potential to be the heaviest period of rain potentially dropping up to to 2 inches in a single 6 hour period Wednesday evening. This is due to a strong 500 mb vort max along with the emergence of the coastal low. This coastal low will continue to deepen due to strong diabatic influences and could deepen more than models are predicting. GFS predicts the precip to stick around through the day on Thursday despite the advance of cool dry air from the NW. It will be a figurative battle in regards to which air mass wins out... either the dry continental air or the moist tropical air. NAM finally starting to come into agreement with the GFS.
Now looking at statewide 3 inch storm total with 6-8 inches possible along the coastal plain. Will go ahead and call 4-5 inches storm total in the triangle region.
Wind also could be a major factor on Wednesday and Thursday as the Coastal low and Great Lakes High create an area of enhanced isobaric flow.
HPC is in genera agreement with a sharp cutoff in the western part of the state. I still think low level low will lead to enhanced precip due to orographic lift. RAH is less bullish on rainfall totals... but that may change later today.
Will try and update later today.
Moderate to heavy rain will begin later this afternoon into this evening as isentropic lift increases. Radar trends show showers already near the region. Expect these showers to increase in coverage and intensity as the right entrance region of an upper jet moves over the triangle region later this afternoon and through the night. The potential exists for one to two inches overnight as this feature moves through. Very slight lull in the heavy and widespread precip looks to occur tomorrow morning however, the rain will reintinsify Wednesday afternoon and through the night. In fact it appears that this has the potential to be the heaviest period of rain potentially dropping up to to 2 inches in a single 6 hour period Wednesday evening. This is due to a strong 500 mb vort max along with the emergence of the coastal low. This coastal low will continue to deepen due to strong diabatic influences and could deepen more than models are predicting. GFS predicts the precip to stick around through the day on Thursday despite the advance of cool dry air from the NW. It will be a figurative battle in regards to which air mass wins out... either the dry continental air or the moist tropical air. NAM finally starting to come into agreement with the GFS.
Now looking at statewide 3 inch storm total with 6-8 inches possible along the coastal plain. Will go ahead and call 4-5 inches storm total in the triangle region.
Wind also could be a major factor on Wednesday and Thursday as the Coastal low and Great Lakes High create an area of enhanced isobaric flow.
HPC is in genera agreement with a sharp cutoff in the western part of the state. I still think low level low will lead to enhanced precip due to orographic lift. RAH is less bullish on rainfall totals... but that may change later today.
Will try and update later today.
Monday, November 9, 2009
11/10-11/11 rainfal event
GFS and NAM both depict tropical storm Ida to come ashore late tonight/early tomorrow and interact with a strengthening short wave. A cold air damming high will move into the Great Lakes region as the storm slowly moves east along the Florida Peninsula. This sets up the potential for a significant overrunning event. Latest GFS Isentropic analysis supports this setup.
The NAM has recently trended away from high precip amounts... but I really like this setup for a heavy rain event. Cold dry air will filter in from the north, but it will basically be confined to the surface with warm moist tropical air advecting in strongly from the east just above the surface. I have doubts that the cold dry air at the surface will effect the precip that much if at all. It just looks like a classic setup to me even with the northerly surface winds. Normally I would be concerned about the NAM showing little precip for North Carolina... but in this case I'm quite confident that the GFS is correct. But with that in mind... we are talking about weather forecasting. Now... there will be a sharp cut off in the precip depending up the height of the column of dry air and the "reach" of the moist air. This boundary should be well to our north.
Expect widespread 2-3 inch rainfall amounts w/ potentially higher amounts near the foothills due to additional orographic lifting.
HPC outlook review: Basically 2-3 inch totals statewide except for the far northwest. The have the intensity increasing from NW to SE. This depiction does make some sense, although I am concerned a bit more with orographic effects.
RAH AFD review: RAH in basic agreement, but they do a nice job of mentioning the upper level features associated with the heavy rainfall including two instances of favorable jet dynamics due to the settling of the quasi irregular troughiness (i.e. merging of the deepening northern trough with the weakening southern trough.). Also, they point out the dynamic effect of latent heat release leading to an enhanced PV anomaly off the coast. This is the kicker for the enhanced rainfall along the coast. Will really need to keep an eye on this for some unexpected very rapid deepening which could lead to enhanced rain even for the triangle. Although, dry air should be pretty well mixed in through high enough in the column to keep the moisture off the coast. But again these thermodynamic effects need to be watched.
Forgot to mention the high wind potential Wednesday as the coastal develops. Could see some pretty good gusts with the high over the lakes and a deeping cyclone off the coast. This should be a fun storm.
The NAM has recently trended away from high precip amounts... but I really like this setup for a heavy rain event. Cold dry air will filter in from the north, but it will basically be confined to the surface with warm moist tropical air advecting in strongly from the east just above the surface. I have doubts that the cold dry air at the surface will effect the precip that much if at all. It just looks like a classic setup to me even with the northerly surface winds. Normally I would be concerned about the NAM showing little precip for North Carolina... but in this case I'm quite confident that the GFS is correct. But with that in mind... we are talking about weather forecasting. Now... there will be a sharp cut off in the precip depending up the height of the column of dry air and the "reach" of the moist air. This boundary should be well to our north.
Expect widespread 2-3 inch rainfall amounts w/ potentially higher amounts near the foothills due to additional orographic lifting.
HPC outlook review: Basically 2-3 inch totals statewide except for the far northwest. The have the intensity increasing from NW to SE. This depiction does make some sense, although I am concerned a bit more with orographic effects.
RAH AFD review: RAH in basic agreement, but they do a nice job of mentioning the upper level features associated with the heavy rainfall including two instances of favorable jet dynamics due to the settling of the quasi irregular troughiness (i.e. merging of the deepening northern trough with the weakening southern trough.). Also, they point out the dynamic effect of latent heat release leading to an enhanced PV anomaly off the coast. This is the kicker for the enhanced rainfall along the coast. Will really need to keep an eye on this for some unexpected very rapid deepening which could lead to enhanced rain even for the triangle. Although, dry air should be pretty well mixed in through high enough in the column to keep the moisture off the coast. But again these thermodynamic effects need to be watched.
Forgot to mention the high wind potential Wednesday as the coastal develops. Could see some pretty good gusts with the high over the lakes and a deeping cyclone off the coast. This should be a fun storm.
Friday, September 25, 2009
Myrtle Beach Forecast
Saturday afternoon: A 40% chance of showers and storms. Precip less than .1 inches.
Saturday night: A 60% chance of showers and storms. Precip .25 - .5 inches.
Sunday: A 60% chance of showers and storms before noon, but mainly earlier in the morning. A 20% chance between noon and 2 PM with clouds decreasing after noon. High 84 but a bit lower on the beach.
Sunday night: Clearing skies
Monday: Partly cloudy with a 20% chance of late afternoon storms. Precip less than .1 inches High 86 but lower on the beach.
Monday night: Partly cloudy with a 20% chance of showers/storms in the evening. Precip less than .1 inches.
Tuesday: Clear and cooler with a high of 78.
Saturday night: A 60% chance of showers and storms. Precip .25 - .5 inches.
Sunday: A 60% chance of showers and storms before noon, but mainly earlier in the morning. A 20% chance between noon and 2 PM with clouds decreasing after noon. High 84 but a bit lower on the beach.
Sunday night: Clearing skies
Monday: Partly cloudy with a 20% chance of late afternoon storms. Precip less than .1 inches High 86 but lower on the beach.
Monday night: Partly cloudy with a 20% chance of showers/storms in the evening. Precip less than .1 inches.
Tuesday: Clear and cooler with a high of 78.
Saturday, September 19, 2009
Past forecast verification and analysis:
Updates:
Synoptic Analysis:
Near term (12 hr): The central US is currently under a broad closed off upper level trough. This will open up and slowly move eastward over the next 12 hours. Precipitation is falling along the eastern slope of the long wave. Precip should remain to our west during the near term however cloud cover is relatively abundant. Could see some breaks in the clouds however... so will go low 80's for the high.
Short term ( 12 -72 hr): High pressure in New England will slowly drift off the coast... however.. winds will continue to circulate clockwise around the high providing us with an ENE surface breeze. Moisture near the surface should remain abundant therefore expect mostly cloudy conditions to continue through the short term. A low pressure system looks to approach from well off the Florida coast. This will take the typical Hatteras curve if you will. This could affect our weather later in the short term. in the more immediate short term don't really see a good lifting mechanism except for very slight isentropic upglide... just enough to mention drizzle. Will keep temps slightly below climatology. Both NAM and GFS support this... Soundings don't even really show much in the way of drizzle so will just mention 20 pop for showers or light drizzle. It does look like some upslope will occur in the foothills but this obviously won't effect us. Looks like any precip that may effect us from the subtropical low would not occur until after the short term.
Long term (Only if a legit major system is showing up): Very quick beach forecast for next weekend. GFS showing a decent cold front moving through on Sunday. Most of the dynamics will be to the north with this front and should mention that GFS shows a cold bias especially in the long term. This would effect the strength of the lift associated with the front and the amount of cold air behind it. The high is likely a bit too strong and well too far south in the latest run. Looks like a chance of rain Saturday and Sunday with clearing on Monday but timing will most likely change. The trough looks much too strong for this time of the year and therefore the amount of cold air flowing in from the north looks fairly ridiculous.
Forecast:
Saturday: Mostly cloudy High 80 Low 63
Sunday: Mostly cloudy with a 20% chance of showers or drizzle High 80 Low 63
Monday: Mostly cloudy with a 20% chance of showers or drizzle High 81 Low 63
Review of RAH AFD:
Updates:
Synoptic Analysis:
Near term (12 hr): The central US is currently under a broad closed off upper level trough. This will open up and slowly move eastward over the next 12 hours. Precipitation is falling along the eastern slope of the long wave. Precip should remain to our west during the near term however cloud cover is relatively abundant. Could see some breaks in the clouds however... so will go low 80's for the high.
Short term ( 12 -72 hr): High pressure in New England will slowly drift off the coast... however.. winds will continue to circulate clockwise around the high providing us with an ENE surface breeze. Moisture near the surface should remain abundant therefore expect mostly cloudy conditions to continue through the short term. A low pressure system looks to approach from well off the Florida coast. This will take the typical Hatteras curve if you will. This could affect our weather later in the short term. in the more immediate short term don't really see a good lifting mechanism except for very slight isentropic upglide... just enough to mention drizzle. Will keep temps slightly below climatology. Both NAM and GFS support this... Soundings don't even really show much in the way of drizzle so will just mention 20 pop for showers or light drizzle. It does look like some upslope will occur in the foothills but this obviously won't effect us. Looks like any precip that may effect us from the subtropical low would not occur until after the short term.
Long term (Only if a legit major system is showing up): Very quick beach forecast for next weekend. GFS showing a decent cold front moving through on Sunday. Most of the dynamics will be to the north with this front and should mention that GFS shows a cold bias especially in the long term. This would effect the strength of the lift associated with the front and the amount of cold air behind it. The high is likely a bit too strong and well too far south in the latest run. Looks like a chance of rain Saturday and Sunday with clearing on Monday but timing will most likely change. The trough looks much too strong for this time of the year and therefore the amount of cold air flowing in from the north looks fairly ridiculous.
Forecast:
Saturday: Mostly cloudy High 80 Low 63
Sunday: Mostly cloudy with a 20% chance of showers or drizzle High 80 Low 63
Monday: Mostly cloudy with a 20% chance of showers or drizzle High 81 Low 63
Review of RAH AFD:
Monday, September 14, 2009
Past forecast verification and analysis: High yesterday was 82 with a low of 67. Anything within 3 degrees I consider verified. High of 87 on Saturday. I just should have took a closer look at the sat to get closer on that one. Bottom dropped out Sunday morning due to inversion setting up.
Updates:
Synoptic Analysis: Seasonably warm and dry conditions will continue through the evening. Clouds will increase on Wednesday with seasonable temperatures.
Near term (12 hr): Same basic story as last forecast period. Large stream of dry air aloft is keeping all cloudiness away. Expect temps to soar into the upper 80's thanks to abundant sunshine. Will lower Saturday's forecast temp for Monday a couple of degrees due to current temp readings. Expect an inversion to setup this morning as opposed to last night due to very dry and calm conditions. Will bottom out temps to 60.
Short term ( 12 -72 hr): Upper level low stays to the west through the short term, but winds do begin to shift to SW at the surface. Flow from off the coast is takes a long track therefore expect modification of any moisture as it mixes with dry air currently in our region. Don't feel good about precip through Wedn. So won't even mention it even as the upper level low slowly drifts toward the east.
Long term (Only if a legit major system is showing up): Upper level low will be a factor in the long term but won't get into any specifics yet. But will say that could be some decent precip near the end of the week.
Forecast:
Monday: Sunny with a high of 88 Low near 60
Tuesday: Mostly Sunny with a high of 88 low near 63
Wednesday: Mostly sunny with increasing clouds in the afternoon. high of 85 Low near 65
Review of RAH AFD:
Updates:
Synoptic Analysis: Seasonably warm and dry conditions will continue through the evening. Clouds will increase on Wednesday with seasonable temperatures.
Near term (12 hr): Same basic story as last forecast period. Large stream of dry air aloft is keeping all cloudiness away. Expect temps to soar into the upper 80's thanks to abundant sunshine. Will lower Saturday's forecast temp for Monday a couple of degrees due to current temp readings. Expect an inversion to setup this morning as opposed to last night due to very dry and calm conditions. Will bottom out temps to 60.
Short term ( 12 -72 hr): Upper level low stays to the west through the short term, but winds do begin to shift to SW at the surface. Flow from off the coast is takes a long track therefore expect modification of any moisture as it mixes with dry air currently in our region. Don't feel good about precip through Wedn. So won't even mention it even as the upper level low slowly drifts toward the east.
Long term (Only if a legit major system is showing up): Upper level low will be a factor in the long term but won't get into any specifics yet. But will say that could be some decent precip near the end of the week.
Forecast:
Monday: Sunny with a high of 88 Low near 60
Tuesday: Mostly Sunny with a high of 88 low near 63
Wednesday: Mostly sunny with increasing clouds in the afternoon. high of 85 Low near 65
Review of RAH AFD:
Saturday, September 12, 2009
Sat Sept 12
Past forecast verification and analysis: Despite the lack of rain the 20 % coverage of showers was warranted with some shower activity to the east. High of 82 and low of 62 which was very close to the predicted min/max.
Updates:
Synoptic Analysis: Dry and and seasonable conditions will continue today and tomorrow with a slight warming trend beginning by the beginning of the week.
Near term (12 hr): Very strong upper level cut off low currently spinning in the Dakotas doesn't look to have a direct effect on the weather in the Triangle. Cary still finds itself under a fairly weak but pretty well dugout trough which extends into the deep south. being located within the trough has resulted in substinence and dry weather the past several days. Some weak vorticity could move in from the north this evening. Moisture is quite limited so won't even mention any associated precip. Maybe some light cloud cover over night will support lows in the mid 60's as upposed to bottoming out in the low 60's
Short term ( 12 -72 hr): A strong upper level low will develop over the Ozarks region and drift slowly east near the end of the short term. This shouldn't directly impact raleigh weather during the short term. The indirect effect will be due to the surface low formation southeast of the upper air disturbance. This will provide us with southwesterlies at the surface due to the ccw around the surface low. Potential for showers looks limited due to a lack of moisture. Some flow off the Atlantic takes a round about route to get to the triangle therefore expect any moist air to modify before it flows into the triangle. This system will likely provide us with a decent chance of showers and storms by the middle/end of next week.
Long term (Only if the potential for a legit major storm or other weather event exists):
Forecast:
Saturday: Variable clouds with a high of 84 low 64
Sunday: Partly cloudy high of 84 low 63
Monday: Partly cloudy high of 90 low 64
Review of RAH AFD:
Updates:
Synoptic Analysis: Dry and and seasonable conditions will continue today and tomorrow with a slight warming trend beginning by the beginning of the week.
Near term (12 hr): Very strong upper level cut off low currently spinning in the Dakotas doesn't look to have a direct effect on the weather in the Triangle. Cary still finds itself under a fairly weak but pretty well dugout trough which extends into the deep south. being located within the trough has resulted in substinence and dry weather the past several days. Some weak vorticity could move in from the north this evening. Moisture is quite limited so won't even mention any associated precip. Maybe some light cloud cover over night will support lows in the mid 60's as upposed to bottoming out in the low 60's
Short term ( 12 -72 hr): A strong upper level low will develop over the Ozarks region and drift slowly east near the end of the short term. This shouldn't directly impact raleigh weather during the short term. The indirect effect will be due to the surface low formation southeast of the upper air disturbance. This will provide us with southwesterlies at the surface due to the ccw around the surface low. Potential for showers looks limited due to a lack of moisture. Some flow off the Atlantic takes a round about route to get to the triangle therefore expect any moist air to modify before it flows into the triangle. This system will likely provide us with a decent chance of showers and storms by the middle/end of next week.
Long term (Only if the potential for a legit major storm or other weather event exists):
Forecast:
Saturday: Variable clouds with a high of 84 low 64
Sunday: Partly cloudy high of 84 low 63
Monday: Partly cloudy high of 90 low 64
Review of RAH AFD:
Wednesday, September 9, 2009
Wednesday September 9
Past forecast verification and analysis: My 50% rain forecast was more than warranted as a surprisingly strong and virtually stalled deformation zone setup over Raleigh. Cary received around half an inch with Raleigh receiving well more than that.
Updates:
Synoptic Analysis: Partly to mostly cloudy skies will be the norm over the next few days with a slight chance of showers over night. Seasonably cool temperatures will continue over the next few days with slight modification as the week comes to an end.
Near term (12 hr):
RDU is currently located under the left exit region of an upper level jet which should provide subsidence along with decreasing clouds in the extreme near term. RDU will be near the center of the upper level low towards the end of the near term. Currrent soundings show a backing profile above at 900 mb which verifies the upper air analysis of subsiding air despite some cloudiness aloft. Expect 500 mb vort max to approach from the west this evening. This could help ignite a shower or two. Will go 20 percent just to cover myself. Any precip should remain light. Partial clearing should aid in temps reaching one cat below climatology. It will be interesting to see if the line of storms to our west hold together.
Short term ( 12 -72 hr):
RDU remains in the trough through the short term. The strength of the trough weakens a bit and then restrengthens a bit later in the period likely due to some downstream assistance (if you will) from the much stronger trough in the upper plains. A weak low pressure is predicted by the GFS to form in South Carolina, weaken and then restrengthen over the Gulf Stream. Can't rule out a chance of showers and storms Friday afternoon and evening due to this weak surface low and some weak vorticity aloft. The upper air dynamics truly are weak though. It's difficult to tell whether or not RDU is truly in the left exit region of a jet or if my eyes are just seeing things. At this time I just don't see enough evidence to warrant and pops. Will go with slightly below persistent high for tomorrow due to some weak CAA along with residual cloud cover. Air will modify a bit on Friday.
Long term (Only if a legit major system is showing up):
Forecast:
Wednesday: Decreasing clouds with a high of 81. 20% chance of showers/storms tonight low of 61
Thursday: Partly cloudy high 79 low 59
Friday: Partly cloudy high 82 low 60
Review of RAH AFD: I said we were under the LE region of a jet which leads to subsidence. Just a mental mistake on my part as the LE leads to rising air, which I knew. Just not thinking clear this morning. I need to double check myself when typing stuff up. If I ever put something like that out in public I'd get called out big time by the weather nerds.
Updates:
Synoptic Analysis: Partly to mostly cloudy skies will be the norm over the next few days with a slight chance of showers over night. Seasonably cool temperatures will continue over the next few days with slight modification as the week comes to an end.
Near term (12 hr):
RDU is currently located under the left exit region of an upper level jet which should provide subsidence along with decreasing clouds in the extreme near term. RDU will be near the center of the upper level low towards the end of the near term. Currrent soundings show a backing profile above at 900 mb which verifies the upper air analysis of subsiding air despite some cloudiness aloft. Expect 500 mb vort max to approach from the west this evening. This could help ignite a shower or two. Will go 20 percent just to cover myself. Any precip should remain light. Partial clearing should aid in temps reaching one cat below climatology. It will be interesting to see if the line of storms to our west hold together.
Short term ( 12 -72 hr):
RDU remains in the trough through the short term. The strength of the trough weakens a bit and then restrengthens a bit later in the period likely due to some downstream assistance (if you will) from the much stronger trough in the upper plains. A weak low pressure is predicted by the GFS to form in South Carolina, weaken and then restrengthen over the Gulf Stream. Can't rule out a chance of showers and storms Friday afternoon and evening due to this weak surface low and some weak vorticity aloft. The upper air dynamics truly are weak though. It's difficult to tell whether or not RDU is truly in the left exit region of a jet or if my eyes are just seeing things. At this time I just don't see enough evidence to warrant and pops. Will go with slightly below persistent high for tomorrow due to some weak CAA along with residual cloud cover. Air will modify a bit on Friday.
Long term (Only if a legit major system is showing up):
Forecast:
Wednesday: Decreasing clouds with a high of 81. 20% chance of showers/storms tonight low of 61
Thursday: Partly cloudy high 79 low 59
Friday: Partly cloudy high 82 low 60
Review of RAH AFD: I said we were under the LE region of a jet which leads to subsidence. Just a mental mistake on my part as the LE leads to rising air, which I knew. Just not thinking clear this morning. I need to double check myself when typing stuff up. If I ever put something like that out in public I'd get called out big time by the weather nerds.
Sunday, September 6, 2009
Past day verification and analysis: High 89 Low 63 No precip - w/in one of the high and 2 of the low, so nothing unexpected.
Updates:
Synoptic Analysis: Seasonably warm weather today will give way to seasonable weather for the rest of the week. A weak area of low pressure along the coastal plain will provide a chance of showers on Monday and Tuesday.
Near term (12 hr): Today's forecast from yesterday looks fine. I don't see a reason to make any major changes. Will lower the low and go with persistence. Looks like little in the way of cloud cover tonight despite being under the left exit of a weak upper level jet.
Short term ( 12 -60 hr): A weak cold air damming high will continue to develop and basically stall in New England. Along with that a weak low pressure down stream of the trough... which may be some remnants from the Tropical Storm... will move north along the coastal plain Monday and Tuesday... therefore will bring in a chance of showers Monday night and Tuesday. qpf looks to be on the light side due to a significant lack of moisture. Soundings do become saturated 0z Monday with some light isentropic lift due to some lower level waa. I can't help but think that models may be underdoing the precip a bit even if the surface dynamics are weak. With winds just above the surface from off the coast am thinking there will be enough moisture to squeeze out a few showers at the very least. Both the GFS and the NAM keep the large majority of the precip centered near the surface low along the Carolina coast. The upper level low associated with this system is small in circumference bet packs a pretty decent punch in relation to its size. But lack of moisture looks to be the main issue. Expect temps to be around or slightly below climatology due to cloud cover. The forecast could change based on the location of the upper level low.
Long term (Beyond 60 hr):
The pattern looks to remain virtually the same with a weak damming high to the north and some weak impulses developing near the coast. Will go slight chance Thursday which is the only day the GFS spits out some precip for our region. Climatological temps through the extended.
Forecast:
Sunday afternoon: Partly Cloudy high 88
Sunday night: Mostly clear low 63
Monday: Mostly cloudy with a 50% chance of showers through the night. Precip around .1 inches High 82 Low 65
Tuesday: Mostly cloudy with a 50% chance of showers mainly before noon with a 30% chance form noon through the night. Precip around .1 inches High 82 Low 65
Wednesday: Decreasing clouds. High 83 low 65
Thursday: Mostly cloudy with a 20% chance of showers. High 83 Low 65
Friday: Partly cloudy. High 83 Low 65
Saturday: Partly cloudy. High 83 Low 65
Review of RAH AFD:
Updates:
Synoptic Analysis: Seasonably warm weather today will give way to seasonable weather for the rest of the week. A weak area of low pressure along the coastal plain will provide a chance of showers on Monday and Tuesday.
Near term (12 hr): Today's forecast from yesterday looks fine. I don't see a reason to make any major changes. Will lower the low and go with persistence. Looks like little in the way of cloud cover tonight despite being under the left exit of a weak upper level jet.
Short term ( 12 -60 hr): A weak cold air damming high will continue to develop and basically stall in New England. Along with that a weak low pressure down stream of the trough... which may be some remnants from the Tropical Storm... will move north along the coastal plain Monday and Tuesday... therefore will bring in a chance of showers Monday night and Tuesday. qpf looks to be on the light side due to a significant lack of moisture. Soundings do become saturated 0z Monday with some light isentropic lift due to some lower level waa. I can't help but think that models may be underdoing the precip a bit even if the surface dynamics are weak. With winds just above the surface from off the coast am thinking there will be enough moisture to squeeze out a few showers at the very least. Both the GFS and the NAM keep the large majority of the precip centered near the surface low along the Carolina coast. The upper level low associated with this system is small in circumference bet packs a pretty decent punch in relation to its size. But lack of moisture looks to be the main issue. Expect temps to be around or slightly below climatology due to cloud cover. The forecast could change based on the location of the upper level low.
Long term (Beyond 60 hr):
The pattern looks to remain virtually the same with a weak damming high to the north and some weak impulses developing near the coast. Will go slight chance Thursday which is the only day the GFS spits out some precip for our region. Climatological temps through the extended.
Forecast:
Sunday afternoon: Partly Cloudy high 88
Sunday night: Mostly clear low 63
Monday: Mostly cloudy with a 50% chance of showers through the night. Precip around .1 inches High 82 Low 65
Tuesday: Mostly cloudy with a 50% chance of showers mainly before noon with a 30% chance form noon through the night. Precip around .1 inches High 82 Low 65
Wednesday: Decreasing clouds. High 83 low 65
Thursday: Mostly cloudy with a 20% chance of showers. High 83 Low 65
Friday: Partly cloudy. High 83 Low 65
Saturday: Partly cloudy. High 83 Low 65
Review of RAH AFD:
Saturday, September 5, 2009
Saturday Sept 5
Past day verification and analysis:
Updates:
Synoptic Analysis: Seasonably warm and dry conditions will occur today. A slight cool down tomorrow will bring more seasonable temperatures and continued dry air. There will be a chance of showers by the middle of the week.
Near term (12 hr): The Triangle is down stream of an extremely positively tilted trough axis which stretches from southwest Texas NE into New England. This pattern has led to a surface high near the Great Lakes Region. The circulation around this high pressure has led an easterly wind at the surface. Soundings are dry and expect this to continue through the evening. 850 mb techniques in regards to surface temp seems reasonable due to decent mixing with partly cloudy skies through the day. This technique reveals highs around 90.
Short term ( 12 -60 hr):
The general patter continues. The trough does pinch off an upper level low which begins to shift east towards the end of the short term. A weak surface low develops off the coast down stream of the u shaped isobar arrangement east of the mountains. The setup looks like an extremely weak cold air damming set up. Will go with about persistence tomorrow and follow that up with seasonable conditions on Monday. Nam spits out some showers due to easterly flow around the weak low. GFS keeps things dry. I like the GFS solution for now although can't rule out some weak overrunning on Monday. Will just play it safe and go with chance shower on Monday and will reevaluate tomorrow. This won't be a major rain event so won't worry too much about getting it exactly right too early.
Long term (Beyond 60 hr):
The pattern basically remains the same through the extended. Will go with seasonable to seasonably cool conditions. Will keep things dry as well as the GFS struggles to produce precip due to dry air and stability. Again... can't rule out light overrunning event during the extended but I don't see anything that jumps out at me at this time.... therefore will stick with dry conditions.
Forecast:
Saturday afternoon: Partly cloudy with a high near 90
Saturday night: Partly cloudy Low 65
Sunday: Partly cloudy High 88 Low 66
Monday: Mostly cloudy with a 30% chance of showers High 89 Low 67
Tuesday: Partly Cloudy High 86 Low 65
Wednesday: Partly Cloudy High 85 Low 65
Thursday: Partly Cloudy High 81 Low 65
Friday: Partly Cloudy High 81 Low 65
Review of RAH AFD:
Updates:
Synoptic Analysis: Seasonably warm and dry conditions will occur today. A slight cool down tomorrow will bring more seasonable temperatures and continued dry air. There will be a chance of showers by the middle of the week.
Near term (12 hr): The Triangle is down stream of an extremely positively tilted trough axis which stretches from southwest Texas NE into New England. This pattern has led to a surface high near the Great Lakes Region. The circulation around this high pressure has led an easterly wind at the surface. Soundings are dry and expect this to continue through the evening. 850 mb techniques in regards to surface temp seems reasonable due to decent mixing with partly cloudy skies through the day. This technique reveals highs around 90.
Short term ( 12 -60 hr):
The general patter continues. The trough does pinch off an upper level low which begins to shift east towards the end of the short term. A weak surface low develops off the coast down stream of the u shaped isobar arrangement east of the mountains. The setup looks like an extremely weak cold air damming set up. Will go with about persistence tomorrow and follow that up with seasonable conditions on Monday. Nam spits out some showers due to easterly flow around the weak low. GFS keeps things dry. I like the GFS solution for now although can't rule out some weak overrunning on Monday. Will just play it safe and go with chance shower on Monday and will reevaluate tomorrow. This won't be a major rain event so won't worry too much about getting it exactly right too early.
Long term (Beyond 60 hr):
The pattern basically remains the same through the extended. Will go with seasonable to seasonably cool conditions. Will keep things dry as well as the GFS struggles to produce precip due to dry air and stability. Again... can't rule out light overrunning event during the extended but I don't see anything that jumps out at me at this time.... therefore will stick with dry conditions.
Forecast:
Saturday afternoon: Partly cloudy with a high near 90
Saturday night: Partly cloudy Low 65
Sunday: Partly cloudy High 88 Low 66
Monday: Mostly cloudy with a 30% chance of showers High 89 Low 67
Tuesday: Partly Cloudy High 86 Low 65
Wednesday: Partly Cloudy High 85 Low 65
Thursday: Partly Cloudy High 81 Low 65
Friday: Partly Cloudy High 81 Low 65
Review of RAH AFD:
Wednesday, September 2, 2009
Wednesday 9/2
Past day verification and analysis: It's never felt so good to be wrong. I predicted a typical cold air damming day with drizzle and cool conditions. Instead we had clear skies with a deep blue sky, crisp air and seasonably cool temperatures. It was a perfect early fall day. High: 79 Low: 57
Updates:
Synoptic Analysis: Mostly cloudy skies will persist today along with dry and seasonably cool conditions. The weather will remain seasonable and dry through the extended.
Near term (12 hr): The triangle is under the entrance region of an upper level jet. This jet will shift NW through the day placing Raleigh under the right entrance region. This along with a deepening trough to the west will provide upper level support... however dry air due to a surface high to the north is prevalent in the mid and lower levels... therefore pops will remain at zero. Cloud cover will keep radiational cooling to a minimum. Will go with very slightly less than persistance for high due to cloudiness and and warmer than persistence for the low due to the same reasoning.
Short term ( 12 -60 hr): The basic pattern will persist through the short term... however toward the end RH values increase and a very weak broad surface low develops off the cost. The best 500 mb support stays to the east and RH around 500 mb stays low... As of now expect precip to remain along and off the coast. Will go with dry and seasonable conditions through the period. Temps will warm a bit near the end of the forecast period due to a southerly surface wind along with week waa... do expect mostly cloudy conditions to occur through the period due to remaining below the right entrance region of the weak upper jet streak and down stream of the trough... This same trough will likely have a big impact on the steering of Tropical Storm Erica in the long term...
Long term (Beyond 60 hr):
Forecast:
Wednesday afternoon: Another nice fall day with variable clouds: High 78
Wednesday night: Variable clouds: Low 61
Thursday: Partly to mostly cloudy skies High 80 Low 62
Friday: Partly to mostly cloudy skies High 82 Low 63
Saturday:
Sunday:
Monday
Tuesday:
Review of RAH AFD:
Updates:
Synoptic Analysis: Mostly cloudy skies will persist today along with dry and seasonably cool conditions. The weather will remain seasonable and dry through the extended.
Near term (12 hr): The triangle is under the entrance region of an upper level jet. This jet will shift NW through the day placing Raleigh under the right entrance region. This along with a deepening trough to the west will provide upper level support... however dry air due to a surface high to the north is prevalent in the mid and lower levels... therefore pops will remain at zero. Cloud cover will keep radiational cooling to a minimum. Will go with very slightly less than persistance for high due to cloudiness and and warmer than persistence for the low due to the same reasoning.
Short term ( 12 -60 hr): The basic pattern will persist through the short term... however toward the end RH values increase and a very weak broad surface low develops off the cost. The best 500 mb support stays to the east and RH around 500 mb stays low... As of now expect precip to remain along and off the coast. Will go with dry and seasonable conditions through the period. Temps will warm a bit near the end of the forecast period due to a southerly surface wind along with week waa... do expect mostly cloudy conditions to occur through the period due to remaining below the right entrance region of the weak upper jet streak and down stream of the trough... This same trough will likely have a big impact on the steering of Tropical Storm Erica in the long term...
Long term (Beyond 60 hr):
Forecast:
Wednesday afternoon: Another nice fall day with variable clouds: High 78
Wednesday night: Variable clouds: Low 61
Thursday: Partly to mostly cloudy skies High 80 Low 62
Friday: Partly to mostly cloudy skies High 82 Low 63
Saturday:
Sunday:
Monday
Tuesday:
Review of RAH AFD:
Monday, August 31, 2009
Mon Aug 31
Past day verification and analysis:
Updates:
Synoptic Analysis: Cold air damming will continue today and tomorrow causing unseasonably cool weather. Dry and seasonable weather will occur on Wednesday and Thursday. A chance of afternoon thunderstorms along with seasonably warm conditions through the weeked.
Near term (12 hr): Short AFD today as more attention will be paid to verification later. Chance of light showers and drizzle will continue through the Tuesday due to cold air damming high which will settle over the great lakes region. Will go unseasonably cool this afternoon and two categories below climatology tomorrow. Front will stalled to the east keeping clouds through tomorrow.
Short term ( 12 -60 hr): Cold air damming will begin to erode by mid week but potentially reignite later on Thursday into the night. Will go seasonably cool and mostly cloudy with decreasing clouds in the afternoon on Wednesday. Dry air will hinder precip on Thursday. Potential overrunning even Thursday night as a weak low pressure forms off the coast. Will pay more attention to this tomorrow.
Long term (Beyond 60 hr): Raleigh will stay down stream of the trough axis just west of the mountains. Southerly winds will bring more seasonable temps and increase chances for afternoon convection through the weekend. Will go summer climatological on pops with climatological to a category above for high. Not too worried about timing in the long term.
Forecast:
Monday afternoon: drizzly with scattered showers high 69
Monday night: drizzly with scattered showers low 67
Tuesday: Cloudy with a chance of drizzle High 75 Low 67
Wednesday: Mostly cloudy with decreasing clouds in the afternoon High 81 Low 60
Thursday: Partly cloudy in the morning with increasing clouds in the afternoon High 79 low 64 30% chance showers overnight.
Friday: Cloudy in the morning with decreasing clouds in the afternoon. 30% chance storms High 80 Low 66
Saturday: Partly cloudy with a 30% chance afternoon storms high 84 low 67
Sunday: Partly cloudy with a 30% chance of afternoon storms high 86 low 69
Review of RAH AFD:
Updates:
Synoptic Analysis: Cold air damming will continue today and tomorrow causing unseasonably cool weather. Dry and seasonable weather will occur on Wednesday and Thursday. A chance of afternoon thunderstorms along with seasonably warm conditions through the weeked.
Near term (12 hr): Short AFD today as more attention will be paid to verification later. Chance of light showers and drizzle will continue through the Tuesday due to cold air damming high which will settle over the great lakes region. Will go unseasonably cool this afternoon and two categories below climatology tomorrow. Front will stalled to the east keeping clouds through tomorrow.
Short term ( 12 -60 hr): Cold air damming will begin to erode by mid week but potentially reignite later on Thursday into the night. Will go seasonably cool and mostly cloudy with decreasing clouds in the afternoon on Wednesday. Dry air will hinder precip on Thursday. Potential overrunning even Thursday night as a weak low pressure forms off the coast. Will pay more attention to this tomorrow.
Long term (Beyond 60 hr): Raleigh will stay down stream of the trough axis just west of the mountains. Southerly winds will bring more seasonable temps and increase chances for afternoon convection through the weekend. Will go summer climatological on pops with climatological to a category above for high. Not too worried about timing in the long term.
Forecast:
Monday afternoon: drizzly with scattered showers high 69
Monday night: drizzly with scattered showers low 67
Tuesday: Cloudy with a chance of drizzle High 75 Low 67
Wednesday: Mostly cloudy with decreasing clouds in the afternoon High 81 Low 60
Thursday: Partly cloudy in the morning with increasing clouds in the afternoon High 79 low 64 30% chance showers overnight.
Friday: Cloudy in the morning with decreasing clouds in the afternoon. 30% chance storms High 80 Low 66
Saturday: Partly cloudy with a 30% chance afternoon storms high 84 low 67
Sunday: Partly cloudy with a 30% chance of afternoon storms high 86 low 69
Review of RAH AFD:
Sunday, August 30, 2009
Past day verification and analysis:
Updates:
9:16 PM: Upped chances tonight due to precip associated with the northern book end line echo moving up from the south. May lower precip amounts tomorrow based on 0z models. 6z GFS weakens 850 low and centers it south of the area... will wait and see if that trend continues... still expecting a heavy band of precip to set up near the 850 low but may weaken as it moves through the triangle. Expect this band to move through tomorrow morning through lunch.
10:45 PM: 0z NAM has weaker 850 low (compared to GFS) passing very close to the triangle... The NAM actually squeezes out a good 1.25 inches qpf but in a relatively small area. Error margin is pretty and confidence of exact location of heaviest rain is not high. Rain total could be anywhere from .25 to 1.5 inches qpf based on strength and location of 850 low. I'm not staying up for the GFS so will just leave wording as is... but will mention rain mostly occuring in the morning.
Synoptic Analysis:
Cloudy and seasonably cool conditions will persist through the afternoon and early evening. A steady rain and unseasonably cool weather is likely on Monday with chances of scattered showers lasting through the middle of the week. Dry and seasonable conditions will occur at the end of the week.
Near term (12 hr): Will lessen chance of storms for today. Surface front has just passed the region. GSO sounding reveals backing and a mid level capping inversion. Expect CAPE values to remain low despite a good chance for some breaks in the cloud by mid afternoon. NAM sim radar keep precip to our south east where cloud cover is much left prevalent... and where the front has yet to pass. Mechanism for ascent will remain toward our southwest today and this evening. Some elevated convection does exist behind the front and more of this could pop up this afternoon. Temps will be slow to cool as is usually the case. Will go with below climatological chance pops for the afternoon for risk of elevated storms with chance pops late night as the synoptic plays a bigger role.
Short term ( 12 -60 hr):
A low pressure will begin to strengthen slightly and move northeast across North Carolina. Warm air out ahead of this low pressure will surge over cold air provided by a surface high over the great lakes. Expect cold air to dam into the region at the surface. Isentropic upglide will be a primary mechanism for ascent in what looks to be a fairly wide spread precip event to the N and NE of the low level vorticity. The speed and location of the low will determine how much precip falls in Cary. NAM doesn't really seem to be picking up on any damming so will lean toward the GFS which shows us to be in the right entrance region of an upper level jet. The GFS also has the 850mb low traveling directly over the region thus enhancing the precip. This setup looks to dump some significant precip. Tough call on the exact location but will put it all out there and call for an inch. MUCAPE will be limited but isolated thunder is possible. Despite decent shear and helicity severe weather is unlikely due to low CAPE. Conditions will remain cold air damming like after the rain moves through. Drizzly... cool.. cloudy
Long term (Beyond 60 hr):
The high in the NE will begin to weaken and open up and most of the cloudiness will exit the area... however.. the pattern will remain seasonably cool.. but dry
Forecast:
Sunday afternoon: 20% chance of storms this afternoon. precip < .1 inch High 83
Sunday night: 80% chance of showers and storms. Low 70
Monday: 90% chance of rain mainly in the morning. 50% chance overnight. About an inch of precip High 68 Low 65
Tuesday: Mostly cloudy with scattered showers (40%). precip <.1 High 77 Low 62
Wednesday: Mostly sunny high 81 low 61
Thursday (Gameday!): Mostly sunny high 80 Low 61
Friday: Partly cloudy high 80 low 63
Saturday: Partly cloudy high 85 low 68
Review of RAH AFD: RAH believe 850 low is too strong as represented by the GFS... therefore... they went with less qpf. It will be interesting to find out who is right on this one. I mentioned front earlier but I should've mentioned it stalling on the coast.
Updates:
9:16 PM: Upped chances tonight due to precip associated with the northern book end line echo moving up from the south. May lower precip amounts tomorrow based on 0z models. 6z GFS weakens 850 low and centers it south of the area... will wait and see if that trend continues... still expecting a heavy band of precip to set up near the 850 low but may weaken as it moves through the triangle. Expect this band to move through tomorrow morning through lunch.
10:45 PM: 0z NAM has weaker 850 low (compared to GFS) passing very close to the triangle... The NAM actually squeezes out a good 1.25 inches qpf but in a relatively small area. Error margin is pretty and confidence of exact location of heaviest rain is not high. Rain total could be anywhere from .25 to 1.5 inches qpf based on strength and location of 850 low. I'm not staying up for the GFS so will just leave wording as is... but will mention rain mostly occuring in the morning.
Synoptic Analysis:
Cloudy and seasonably cool conditions will persist through the afternoon and early evening. A steady rain and unseasonably cool weather is likely on Monday with chances of scattered showers lasting through the middle of the week. Dry and seasonable conditions will occur at the end of the week.
Near term (12 hr): Will lessen chance of storms for today. Surface front has just passed the region. GSO sounding reveals backing and a mid level capping inversion. Expect CAPE values to remain low despite a good chance for some breaks in the cloud by mid afternoon. NAM sim radar keep precip to our south east where cloud cover is much left prevalent... and where the front has yet to pass. Mechanism for ascent will remain toward our southwest today and this evening. Some elevated convection does exist behind the front and more of this could pop up this afternoon. Temps will be slow to cool as is usually the case. Will go with below climatological chance pops for the afternoon for risk of elevated storms with chance pops late night as the synoptic plays a bigger role.
Short term ( 12 -60 hr):
A low pressure will begin to strengthen slightly and move northeast across North Carolina. Warm air out ahead of this low pressure will surge over cold air provided by a surface high over the great lakes. Expect cold air to dam into the region at the surface. Isentropic upglide will be a primary mechanism for ascent in what looks to be a fairly wide spread precip event to the N and NE of the low level vorticity. The speed and location of the low will determine how much precip falls in Cary. NAM doesn't really seem to be picking up on any damming so will lean toward the GFS which shows us to be in the right entrance region of an upper level jet. The GFS also has the 850mb low traveling directly over the region thus enhancing the precip. This setup looks to dump some significant precip. Tough call on the exact location but will put it all out there and call for an inch. MUCAPE will be limited but isolated thunder is possible. Despite decent shear and helicity severe weather is unlikely due to low CAPE. Conditions will remain cold air damming like after the rain moves through. Drizzly... cool.. cloudy
Long term (Beyond 60 hr):
The high in the NE will begin to weaken and open up and most of the cloudiness will exit the area... however.. the pattern will remain seasonably cool.. but dry
Forecast:
Sunday afternoon: 20% chance of storms this afternoon. precip < .1 inch High 83
Sunday night: 80% chance of showers and storms. Low 70
Monday: 90% chance of rain mainly in the morning. 50% chance overnight. About an inch of precip High 68 Low 65
Tuesday: Mostly cloudy with scattered showers (40%). precip <.1 High 77 Low 62
Wednesday: Mostly sunny high 81 low 61
Thursday (Gameday!): Mostly sunny high 80 Low 61
Friday: Partly cloudy high 80 low 63
Saturday: Partly cloudy high 85 low 68
Review of RAH AFD: RAH believe 850 low is too strong as represented by the GFS... therefore... they went with less qpf. It will be interesting to find out who is right on this one. I mentioned front earlier but I should've mentioned it stalling on the coast.
Friday, August 28, 2009
Fri Aug 28
Past day verification and analysis: No precip high 94 low 72. Precip coverage was less than 30% likely due to dry air aloft along with capping inversion around 650mb. Will take that into account in future forecasts.
Synoptic analysis: A closed low in the deep south will open up and converge with Tropical Storm Danny. Thunderstorm chances will increase this afternoon. A chance of storms will continue on Saturday. A cold front will begin to push into the region on Sunday and stall early next week providing a good chance of showers and thunderstorms. Cooler and drier conditions will invade the region by next week.
Near term (12 hr): A very interesting but fairly difficult forecast. The closed off upper level low will become an open wave and converge with Tropical Storm Danny. The juxtaposition of these two features will create a dynamic and complicated scenario this afternoon. A zone of surface convergence should set up near the piedmont later this afternoon. Upper level support isn't too impressive... still anticipate likely chance for convective development this afternoon. Precip on the wet side of Danny's circulation is hardly in existence with westerly shear having sheared most of the precip to the east of the center... therefore am less concerned with direct precip from Danny. Breaks in the cloud cover should enhance SBCAPE above 2000 J/Kg by this afternoon. PW values of 1.8 to 1.9 inches are currently in the region. There is also no sign of a capping inversion therefore expect storms with heavy rain to develop along regions of convergence. Will go likely PoPs this afternoon and high chance overnight. High around climatology due to cloud cover and low slightly higher than persistence due to the same reasoning.
Short term ( 12 -60 hr): Attention will shift from tropical storm Danny and the upper level low in the south toward the strengthening and transient upper low near the great lakes. A relatively strong cold front will approach the area from west increasing rain chances through Sunday afternoon. We have a good chance for storms Saturday afternoon being in the warm sector. A 500 mb impulse will move through Saturday night therefore will keep high chance PoPs through the night on Saturday. Will go with climatological high and persistent low. Cloud cover and showers will impact lows. Will lower PoPs on Sunday to high chance. Increased shear will improve storm organization, but most of the upper level dynamics will be to the west. Severe threat will increase but not enough to warrant anything other than a mention at this time.
Long term (Beyond 60 hr):
Trough will deepen and the cold front will stall and weaken in the early part of the week bringing a chance for showers and storms on Monday and Tuesday before slowly moving past the region. Will go high chance on Monday and Tuesday. Once confidence grows in the timing of the front and upper level support. Autumn weather will invade the area after the passage of the front through the end of the week.
Forecast:
Friday afternoon: 60% chance of storms with heavy rain possible at times. Precip .25 inches but higher in storms. High 86
Friday night: 40 % chance of showers and storms.. precip less than .1 inches
Saturday: 40 % chance of showers and storms through the night.. precip less than .1 inches High 89 low 72
Sunday: 50 % chance of showers and storms mainly before 10 pm.. precip .1 - .25 inches High 89 low 72
Monday: 40% chance of showers and storms after 2 pm High 85 low 72
Tuesday: 40% chance of showers and storms through the night. High 85 Low 72
Wednesday: Mostly cloudy in the morning partly cloudy in the afternoon High 81 Low 65
Thursday: Partly Cloudy High 79 Low 60
Review of RAH AFD: Need to watch for dry air on Saturday. Keep a good eye out on upper divergence as well. A lot of stuff to look at through with a full forecast. RAH breaks it up into several sections. Precip early next week may be some overrunning. When looking at theta e to determine position of front need to consider that part of the hold up is due to downsloping effect. So I need to look at the pressure field and wind direction to determine if front has passed.
Synoptic analysis: A closed low in the deep south will open up and converge with Tropical Storm Danny. Thunderstorm chances will increase this afternoon. A chance of storms will continue on Saturday. A cold front will begin to push into the region on Sunday and stall early next week providing a good chance of showers and thunderstorms. Cooler and drier conditions will invade the region by next week.
Near term (12 hr): A very interesting but fairly difficult forecast. The closed off upper level low will become an open wave and converge with Tropical Storm Danny. The juxtaposition of these two features will create a dynamic and complicated scenario this afternoon. A zone of surface convergence should set up near the piedmont later this afternoon. Upper level support isn't too impressive... still anticipate likely chance for convective development this afternoon. Precip on the wet side of Danny's circulation is hardly in existence with westerly shear having sheared most of the precip to the east of the center... therefore am less concerned with direct precip from Danny. Breaks in the cloud cover should enhance SBCAPE above 2000 J/Kg by this afternoon. PW values of 1.8 to 1.9 inches are currently in the region. There is also no sign of a capping inversion therefore expect storms with heavy rain to develop along regions of convergence. Will go likely PoPs this afternoon and high chance overnight. High around climatology due to cloud cover and low slightly higher than persistence due to the same reasoning.
Short term ( 12 -60 hr): Attention will shift from tropical storm Danny and the upper level low in the south toward the strengthening and transient upper low near the great lakes. A relatively strong cold front will approach the area from west increasing rain chances through Sunday afternoon. We have a good chance for storms Saturday afternoon being in the warm sector. A 500 mb impulse will move through Saturday night therefore will keep high chance PoPs through the night on Saturday. Will go with climatological high and persistent low. Cloud cover and showers will impact lows. Will lower PoPs on Sunday to high chance. Increased shear will improve storm organization, but most of the upper level dynamics will be to the west. Severe threat will increase but not enough to warrant anything other than a mention at this time.
Long term (Beyond 60 hr):
Trough will deepen and the cold front will stall and weaken in the early part of the week bringing a chance for showers and storms on Monday and Tuesday before slowly moving past the region. Will go high chance on Monday and Tuesday. Once confidence grows in the timing of the front and upper level support. Autumn weather will invade the area after the passage of the front through the end of the week.
Forecast:
Friday afternoon: 60% chance of storms with heavy rain possible at times. Precip .25 inches but higher in storms. High 86
Friday night: 40 % chance of showers and storms.. precip less than .1 inches
Saturday: 40 % chance of showers and storms through the night.. precip less than .1 inches High 89 low 72
Sunday: 50 % chance of showers and storms mainly before 10 pm.. precip .1 - .25 inches High 89 low 72
Monday: 40% chance of showers and storms after 2 pm High 85 low 72
Tuesday: 40% chance of showers and storms through the night. High 85 Low 72
Wednesday: Mostly cloudy in the morning partly cloudy in the afternoon High 81 Low 65
Thursday: Partly Cloudy High 79 Low 60
Review of RAH AFD: Need to watch for dry air on Saturday. Keep a good eye out on upper divergence as well. A lot of stuff to look at through with a full forecast. RAH breaks it up into several sections. Precip early next week may be some overrunning. When looking at theta e to determine position of front need to consider that part of the hold up is due to downsloping effect. So I need to look at the pressure field and wind direction to determine if front has passed.
Thursday, August 27, 2009
Thursday Aug 27
Past day verification and analysis: Low of 70 with no precip - I predicted a low of around 70 for the evening forecast/Thursday low... I'm off to a good start.
Synoptic analysis:
Upper level low in the SE will begin to shift eastward today. Chance of afternoon storms today as the dry stream of air lifts north of the region. Danny will approach the Outer Banks Friday afternoon/evening and potentially interact with upper level support to increase storm chances. A cold front will move through Sunday enhancing the chances for Thunderstorm activity. Moisture is limited but available with PW values exceeding 1.2 inches.
Near term (12 hr):
NAM is showing an increased chance of convection later this afternoon centered over the northern piedmont. SBCAPE has already exceeded 2500 J/Kg. Storms will be scattered and unorganized due to a lack of sufficient shear. The stream of dry air in the upper atmosphere has shifted to our north based on water vapor. Initiation of storms looks to be a weak pressure anomaly at the surface based on the latest RUC. This is currently located just west of Winston Salem. Severe winds due to downdrafts are possible this afternoon. NCAPE values are not too impressive but can't rule out small hail and weak downdrafts if storms develop. Will go with climatological chance PoPs for the triangle without mention of severe. Will lower temps slightly due to enhanced cumulus cloud cover this afternoon. No reason not to stick with persistence on the overnight low.
Short term ( 12 -36 hr):
In the short term concentration shifts towards the impact of the deep south upper level low and tropical storm Danny. Current guidance has Danny moving just east of the Carolina coast and northward toward Boston. 12z Nam has the track shifted slightly west. Although... I will strictly follow NHC/HPC guidelines for now. The interesting part is how Danny will interact with the upper low over the deep south which is forecast to shift east. The closed low will lift and become open toward the end of the short term. 500 mb vort max will approach late in the day on Friday. At the same time a zone of convergence could form from the juxtaposition of Danny and southerlies ahead of a low pressure in Indiana. The thinking is that a band of showers and storms will set up near the triangle due to all of these factors.... Therefore will go with greater than climatological chances of precip on Friday. Also, could see bands directly associated with Danny also effect the eastern piedmont. Will go with climatological temps despite southerly winds due to clouds associated with Danny. These clouds also might reduce available convective potential cenergy... but not enough to lower PoPs.
Long term (Beyond 36 hr):
The open wave in the deep south will lift out of the region and focus will shift toward a deepening upper level low near the great lakes which will eventually become closed. Latest model guidance is stronger and more transient with the upper low. The triangle will be under the right entrance region of the upper level jet associated with this closed low. A surface low will move down stream of the upper low and eventually become stacked. A relatively strong trailing cold front for this time of year will approach the region on Sunday afternoon. GFS theta e analysis shows the cold front not moving through until Tuesday afternoon (oh the agony). Therefore the GFS shows storms developing on Sunday and Monday. Not currently confident that the cold front will stall over the region on Monday therefore will only go with slight chance PoPs... but do feel confident that numerous storms will develop on Sunday to warrant likely PoPs. Will go above climatology on Saturday afternoon due to being in the warm sector, therefore enough instability should exist to warrant high chance. Will keep an eye on the severe threat on Sunday as shear and helicity will be enhanced due to better upper level support. Will keep temps at climatology due to increased cloud coverage. After cold front moves through expect dry and cooler conditions.
Forecast:
Wednesday afternoon: 30% chance of storms. Precip less than .1 inch except higher in storms. High 93
Thursday night: 30% chance of showers and storms before 10 PM. Low around 70.
Friday: 50% chances of storms mainly after 2 PM. 40 % chance of storms through the night. High 87 Low 72 precip .25 inches
Saturday: 30% chance of storms in the afternoon. High 88 low 71. precip less than .1 inches
Sunday: 60% chance of storms mainly after 2 pm. high 86 low 71. precip .3 inches
Monday: 30% chance of storms mainly after 2 pm. high 85 low 68. precip less than .1 inches
Tuesday: Mostly cloudy giving way to sun in the afternoon high 83 low 60
Wednesday: Clear and seasonably cool high 80 low 60
Review of RAH AFD: Near term: I took a look at the sounding but I missed the inversion layer in the mid atmosphere. It looks like that has a good chance to be overcome though. I'll be sure to look for that next time.
Synoptic analysis:
Upper level low in the SE will begin to shift eastward today. Chance of afternoon storms today as the dry stream of air lifts north of the region. Danny will approach the Outer Banks Friday afternoon/evening and potentially interact with upper level support to increase storm chances. A cold front will move through Sunday enhancing the chances for Thunderstorm activity. Moisture is limited but available with PW values exceeding 1.2 inches.
Near term (12 hr):
NAM is showing an increased chance of convection later this afternoon centered over the northern piedmont. SBCAPE has already exceeded 2500 J/Kg. Storms will be scattered and unorganized due to a lack of sufficient shear. The stream of dry air in the upper atmosphere has shifted to our north based on water vapor. Initiation of storms looks to be a weak pressure anomaly at the surface based on the latest RUC. This is currently located just west of Winston Salem. Severe winds due to downdrafts are possible this afternoon. NCAPE values are not too impressive but can't rule out small hail and weak downdrafts if storms develop. Will go with climatological chance PoPs for the triangle without mention of severe. Will lower temps slightly due to enhanced cumulus cloud cover this afternoon. No reason not to stick with persistence on the overnight low.
Short term ( 12 -36 hr):
In the short term concentration shifts towards the impact of the deep south upper level low and tropical storm Danny. Current guidance has Danny moving just east of the Carolina coast and northward toward Boston. 12z Nam has the track shifted slightly west. Although... I will strictly follow NHC/HPC guidelines for now. The interesting part is how Danny will interact with the upper low over the deep south which is forecast to shift east. The closed low will lift and become open toward the end of the short term. 500 mb vort max will approach late in the day on Friday. At the same time a zone of convergence could form from the juxtaposition of Danny and southerlies ahead of a low pressure in Indiana. The thinking is that a band of showers and storms will set up near the triangle due to all of these factors.... Therefore will go with greater than climatological chances of precip on Friday. Also, could see bands directly associated with Danny also effect the eastern piedmont. Will go with climatological temps despite southerly winds due to clouds associated with Danny. These clouds also might reduce available convective potential cenergy... but not enough to lower PoPs.
Long term (Beyond 36 hr):
The open wave in the deep south will lift out of the region and focus will shift toward a deepening upper level low near the great lakes which will eventually become closed. Latest model guidance is stronger and more transient with the upper low. The triangle will be under the right entrance region of the upper level jet associated with this closed low. A surface low will move down stream of the upper low and eventually become stacked. A relatively strong trailing cold front for this time of year will approach the region on Sunday afternoon. GFS theta e analysis shows the cold front not moving through until Tuesday afternoon (oh the agony). Therefore the GFS shows storms developing on Sunday and Monday. Not currently confident that the cold front will stall over the region on Monday therefore will only go with slight chance PoPs... but do feel confident that numerous storms will develop on Sunday to warrant likely PoPs. Will go above climatology on Saturday afternoon due to being in the warm sector, therefore enough instability should exist to warrant high chance. Will keep an eye on the severe threat on Sunday as shear and helicity will be enhanced due to better upper level support. Will keep temps at climatology due to increased cloud coverage. After cold front moves through expect dry and cooler conditions.
Forecast:
Wednesday afternoon: 30% chance of storms. Precip less than .1 inch except higher in storms. High 93
Thursday night: 30% chance of showers and storms before 10 PM. Low around 70.
Friday: 50% chances of storms mainly after 2 PM. 40 % chance of storms through the night. High 87 Low 72 precip .25 inches
Saturday: 30% chance of storms in the afternoon. High 88 low 71. precip less than .1 inches
Sunday: 60% chance of storms mainly after 2 pm. high 86 low 71. precip .3 inches
Monday: 30% chance of storms mainly after 2 pm. high 85 low 68. precip less than .1 inches
Tuesday: Mostly cloudy giving way to sun in the afternoon high 83 low 60
Wednesday: Clear and seasonably cool high 80 low 60
Review of RAH AFD: Near term: I took a look at the sounding but I missed the inversion layer in the mid atmosphere. It looks like that has a good chance to be overcome though. I'll be sure to look for that next time.
Tuesday, August 25, 2009
Wed. 8/26 Forecast
Past day verification and analysis: NA
Synoptic analysis:
Closed upper level low low pressure currently located over the deep south along with a surface high over the southern Apps will lead to dry warm conditions through today and into tonight.
Near term (12 hr):
A strong upper level low is centered near Mississippi. HPC has drawn a pair of high pressures along the southern Appalachians. These 2 features have combined to form subsidence leading to a warm dry environment. The air above 650 mb is extremely dry which can be seen on water vapor and current soundings out of GSO. Expect this pattern to continue through the night. Cloud cover over night should be minimal due to the subsidence and dry air. Also, expect the inversion layer to keep surface winds relatively calm.
Short term ( 12 -36 hr):
The warm dry pattern will continue in the short term with the upper level low slowly shifting eastward. However... models show a weak impulse entering the forecast region at around 0z Friday... which should enhance shower chances Friday. Moisture levels are marginal and neither the NAM nor the GFS are bullish with QPF so will go with only summer climatological chances for Friday afternoon. CAPE and associated convection appear to be limited due to afternoon cloud cover Friday afternoon. This implies surface temps on Friday will be lower then persistance by several degrees. If cloud cover is not a factor on Friday then expect a good chance of afternoon thunderstorms.
Long term (Beyond 36 hr):
The long term starts out messy as the upper level low shifts east and interacts with Tropical Storm Danny. NHC currently predicts Danny to move just off the North Carolina shore. CCW winds around Danny could interact with SW winds along a surface low in Tennessee.... which could create a zone of convergence Saturday afternoon... moisture is limited however. Will go chance PoPs Saturday afternoon. A closed low will set up later in the forecast period as Danny exits the region. The associated trough will deepen... expect impulses to ride along this trough enhancing the chances for precip later in the weekend and into early next week. The trough will hold on but dampen as the middle of the week nears. The timing of these impulses are anyones guess in the long range. A cold front will come through sometime during the day on Monday. After this a relatively strong high pressure will build in from the west. Will stick with chance pops through Monday with partly cloudy skies on Sunday. Highs will be slightly below climatology due to expected cloud cover associated with any impulses.
Forecast:
Wed night: Clear with a low around 70
Thursday: Sunny and hot.. High 95 low near 70
Friday: 30% chance of storms.. precip less than .1 inches.. High 85 Low 69
Saturday: 30% chance of storms.. precip less than .1 inches.. High 85 low 70
Sunday: 30% chance of afternoon storms.. precip less than .1 inches.. High 82 low 70
Monday: 30% chance of afternoon storms.. precip less than .1 inches.. High 82 low 70
Tuesday: Partly Sunny.. High 82 low 70
Synoptic analysis:
Closed upper level low low pressure currently located over the deep south along with a surface high over the southern Apps will lead to dry warm conditions through today and into tonight.
Near term (12 hr):
A strong upper level low is centered near Mississippi. HPC has drawn a pair of high pressures along the southern Appalachians. These 2 features have combined to form subsidence leading to a warm dry environment. The air above 650 mb is extremely dry which can be seen on water vapor and current soundings out of GSO. Expect this pattern to continue through the night. Cloud cover over night should be minimal due to the subsidence and dry air. Also, expect the inversion layer to keep surface winds relatively calm.
Short term ( 12 -36 hr):
The warm dry pattern will continue in the short term with the upper level low slowly shifting eastward. However... models show a weak impulse entering the forecast region at around 0z Friday... which should enhance shower chances Friday. Moisture levels are marginal and neither the NAM nor the GFS are bullish with QPF so will go with only summer climatological chances for Friday afternoon. CAPE and associated convection appear to be limited due to afternoon cloud cover Friday afternoon. This implies surface temps on Friday will be lower then persistance by several degrees. If cloud cover is not a factor on Friday then expect a good chance of afternoon thunderstorms.
Long term (Beyond 36 hr):
The long term starts out messy as the upper level low shifts east and interacts with Tropical Storm Danny. NHC currently predicts Danny to move just off the North Carolina shore. CCW winds around Danny could interact with SW winds along a surface low in Tennessee.... which could create a zone of convergence Saturday afternoon... moisture is limited however. Will go chance PoPs Saturday afternoon. A closed low will set up later in the forecast period as Danny exits the region. The associated trough will deepen... expect impulses to ride along this trough enhancing the chances for precip later in the weekend and into early next week. The trough will hold on but dampen as the middle of the week nears. The timing of these impulses are anyones guess in the long range. A cold front will come through sometime during the day on Monday. After this a relatively strong high pressure will build in from the west. Will stick with chance pops through Monday with partly cloudy skies on Sunday. Highs will be slightly below climatology due to expected cloud cover associated with any impulses.
Forecast:
Wed night: Clear with a low around 70
Thursday: Sunny and hot.. High 95 low near 70
Friday: 30% chance of storms.. precip less than .1 inches.. High 85 Low 69
Saturday: 30% chance of storms.. precip less than .1 inches.. High 85 low 70
Sunday: 30% chance of afternoon storms.. precip less than .1 inches.. High 82 low 70
Monday: 30% chance of afternoon storms.. precip less than .1 inches.. High 82 low 70
Tuesday: Partly Sunny.. High 82 low 70
This is a weather blog for the Triangle of North Carolina. This blog will contain a daily forecast along with an area forecast discussion. Links to forecasting maps and discussions will also be provided so that the viewers of the website can follow along with the discussion. Other random information will also be posted from time to time.
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