Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 4:51 PM GMT on June 03, 2009
Tropical Tidbit from 12:30pm eastern time:
Across the Atlantic and Eastern Pacific things remain very quiet for the beginning of the hurricane season, but we may have a mischievous trouble-maker down the road here playing games in the Caribbean. I'll tell you why.
Right now the current situation is we have a weak area of low pressure (1013mb) near the mouth of the Mississippi River, which formed yesterday under a broad area of showers and thunderstorms in advance of an upper shortwave trough moving through eastern Texas, Arkansas, and western Louisiana. In about a day or so this weak low will move northeast and merge with a cold front which is currently moving through north Texas and NW Arkansas, forming one low pressure system over the SE states that will move NE off the eastern Seaboard in 60-72 hours.
The catch is that a piece of the shortwave trough is going to get left behind near the north gulf coast and split off from the westerlies, along with a surface remnant low. Events like this are called "trough-splits", and are one of the main causes of early-season tropical cyclones in the western Atlantic, especially the Gulf of Mexico and the Caribbean. I put together a little animation of this morning's 06z GFS 500mb 0-180 hours to show you how this occurs:
Now over the next 5-7 days this upper-level piece will drift southward into the NW Caribean, where the GFS forms a surface low at 120 hours. Yes it's shown as a shallow warm-core sub-tropical low, but that is typical of how trough-split systems begin, and it will be over SSTs of 28C. The environment doesn't look very favorable down there right now with the sub-tropical jetstream screaming through the area, but during the next 5 days the models are forecasting the upper high in the eastern Pacific to start moving north and bulging up into Mexico and the western GOM. This, coupled with the upper piece from the GOM moving south, will effectively split the sub-tropical jet over the Caribbean, leaving an area of lower shear for the low to deal with.
This is one of those things that will need to be watched carefully as it evolves. It may not happen at all and the split-off feature may dissipate all-together, but the GFS has been sniffing it out (on the new 12z run also), and it's a possibility worth investigating. Again, trough-splits are one of the main causes of early-season tropical storms, so they deserve attention. I will continue to monitor this area over the next several days.
We shall see what happens!
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