Good afternoon; I'm enjoying a very much needed day off from both college and commuting and I've had a bit of time to look at the upper air charts so let's get started; last night it rained at my house and what got my attention were the movement of the cells; they were south movers. As of 24/12Z; the 500 mb upper ridge is centered over Jackson, MS, it is a 589 (decameter or 5890 meter) upper high. There are general 10 meter height falls in the entire area with height falls in advance of a 582 upper low and a progressive positive tilt shortwave trough over Eastern Nebraska, Kansas and Central Oklahoma. There is a weak 587 upper low near Houston, TX. The longwave trough that has draped the Eastern United States has moved slightly more to the east with lowest heights near Florence, SC extending through Eastern Georgia, east of Tallahassee, FL to a COL near 28N 85W in the Gulf of Mexico; heights east of the longwave trough are neutral from the previous 12 hours with the exceptions a 10 meter height fall at Jacksonville, FL and 30 meters height fall near Charleston, SC where there is a tiny cutoff low along the trough; the height fall at Charleston suggests the trough has moved a bit to the east in the past 12 hours and the mid continental ridge with two centers; one over Mississippi and the other over Northern Mexico. The Bermuda subtropical upper ridge is centered slightly west of Bermuda. A steering path for the moment boils down to whether the GFS is correct or the ECMWF with its more left track is correct. I'm aware NOAA sampled the environment around Issac for the 24/00Z model run but I see no new data on the 12Z upper charts. To date the ECMWF has performed excellent depicting where the strongest of the multiple vortices are...maybe that's pure luck; I said last night the strongest vortices are in the southwest of the broader circulation and clearly today, Issac has consolidated around that point and is much better defined today.
The $64,000 question is where Issac is going and whether Florida will be impacted. The current track suggests Issac will be over land over Cuba for a good bit of time and NHC is right; what structure will it have exiting Cuba. Issac is huge in size and Florida will be affected by both rain and possibly water pushed up ahead by moderate southerly winds on the right size of the system; I see no evidence that Issac will be a major hurricane by the time it reaches the Northern Gulf Coast. Farmers from Alabama to Central Georgia to South Carolina will welcome the rain given much is this area is in a severe to exceptional drought; particularly Central Georgia and parts of Central South Carolina; what will not welcome additional rainfall is Northern Florida and Southeastern Georgia which were impacted by Debby with an excess of two feet of rain between Tallahassee and Appalachacola (don't ask me how to spell it).
The bottom line remains how strong will the upper air players be; what upper ridge will be the strongest and which one will influence east and west the track of Issac. Clearly the general track is set with a trough between the two upper ridges.
The models have a stout 597 upper high over the Intermountain West which means blazing hot weather for them and equally stout near 594 upper ridge in the Atlantic.
I don't see this system stalling; once again it is clear what the track is; a precise point is impossible. I do have concerns about intensity but we are all going to have to wait and see what structure Issac has once in the Florida Straits; until then, it is unrealistic to predict rapid intensification or any other intensities until Issac exits Cuba.
Our thoughts and prayers go out to those in Haiti who were displaced by the earthquake who live up under tents; once the center goes by and the wet side of the storm impacts their country; like Puerto Rico today, it may be a tough weekend that lies ahead for them.
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