Thursday, October 03, 2013

Tropical Storm Karen: October 3, Update A

A special quick update on TS Karen only (Jerry can wait!). The NHC upgraded the Caribbean Blobette directly from 'an area of interest' to a Tropical Storm with 60mph winds, which makes her a mid-strength Tropical Storm (TS range: 39-73mph). A bit behind on the magic ball there... they really should have named her yesterday!

The circulation is very good in the lower half of the troposphere, but there is nothing in the upper levels which is good - this means she's definitely not a hurricane. She did clip the northern tip of the Yucatan Peninsula last night but will shortly move completely away an into the gulf. You can see that she's not completely 'circular' because of this interaction with land in the satellite images (visible on top, infrared below):

The strongest convection is over the area of warmest water... but not only at the surface! It is warmer than 26.5 deg C in the upper ~150m, which is really deep. As she moves away from this part of the northern Caribbean, the warm water depth will decrease, so we should see a reduction in the convection. The other two factors she will bump into in the Gulf is the dry air to her north and west, and a bit stronger wind shear.

As for track, the current forecast has her going into Alabama late on Saturday night:

Looking at the pressure fields I have access to, it looks like she may curve to the east before that point which means the Florida panhandle or the north-central west coast of Florida. But keep in mind that the pressure fields are subject to change and I don't have as good information on this as the NHC. They have been pretty good on the track one day out, and fairly good two days out, so even if she doesn't make a direct line for Alabama, you guys may get a few drops of rain (of course, if the dry air and wind shear really kicks in, you may have a perfectly sunny day).

Must run, but more later,

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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