At the time of yesterday's update, Isidore was a strong TS with a strengthening trend. At 21Z yesterday, he reached CAT1 hurricane status, then at 09Z this morning, reached CAT2 status and low-lying western Cuba (and perhaps the occassional eyewall cycle as the storm re-organizes itself) is the only obstacle to further intensification. The central pressure fell 24mb in the past 24 hours, and 13mb in the past 12 hours, so the storm is not yet qualified as a rapid intensifier (some classic definitions can be found at http://www.nrlmry.navy.mil/~chu/chap6img/tab605.jpg and a recent definition is +31kts/day). It will be a very well-observed storm, in terms of aircraft flights into it, around it, and sensors dropped into the ocean ahead of and under it to record the depth of the warm water (latest data I know about: 29.5-30.0C running 50-70m deep, which is an amazing amount of energy available to this storm... it's a 230'-deep bathtub of 86F water!). At 15Z, Hurricane Isidore was located at 21.7N 83.9W (just a few miles south of the western Cuban coast) and tracking WNW at 7kts. Maximum sustained winds have reached 90kts and the MSLP has plummeted to 966mb. Despite this low pressure, an eye has still not formed, which from my experience is very unusual. However, the inner precipitation structure -as revealed by microwave imagery- does contain the mature features one would expect from a 966mb hurricane. A Hurricane Watch and Tropical Storm Warning are in effect for most of the northern Yucatan Peninsula, and a Hurricane Warning is still in effect for all of western Cuba and the Isle of Youth. You can download and print a high-quality map from http://www.mcwar.org/gallery/tropics/MESO_atl_blank.ps if you wish to keep up with the track of this storm. The intensity forecast is relatively simple for a change... it's in a very favorable environment; both the ocean and the atmosphere will allow it to continue to strengthen, seemingly well into the major hurricane domain (CAT3, 4, 5). However, just to keep the operational tropical meteorologists on their toes, the track is far from trivial to forecast. It's hard to find even two models that agree on a scenario, let alone a concensus. The official NHC forecast takes Isidore past western Cuba and into the southeastern Gulf, slows him down and turns him slightly westward. This seems quite reasonable, and after that, I suspect some sort of a more northward turn, in advance of the next trough. At any rate, the US is not threatened by landfall through the end of the weekend, but should be taking that time to prepare for one. Elsewhere, there's a broad circulation with a 1010mb Low and scattered deep convection at about 29N 52W (roughly 14 degrees ESE of Bermuda). Vertical shear is fairly low, the SST there is about 27.5C, but the vorticity center is still somewhat elongated and disorganized. Should this develop, the next number/name on deck is 12/Kyle.
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