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.
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