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August 2013

Tropical Development Possible Next Week in the NW Caribbean or Gulf of Mexico

   Posted by Levi at 1:22am on August 9, 2013

There are currently no significant tropical disturbances in the Atlantic, but one is likely to form in the western Caribbean next week, and will have a good shot at developing into a tropical cyclone. The originating feature is a broad, deep-layer wave of low pressure located east of the lesser Antilles, most pronounced at the 500mb level in 18z GFS analysis. This is the system I mentioned in my video on Sunday as a potential threat next week. Although there are currently few clouds associated with this feature, that should change in a few days. The wave will move westward through the Caribbean, and once west of 75-80W, it will serve as a brake on the trade wind flow coming in behind it from the east. This will cause air to pile up and rise in the western Caribbean, and widespread thunderstorms will likely result. This will likely happen in 5-7 days, resulting in at least a weak area of low pressure in the western Caribbean.

As the low moves northwestward, it will be moving into a progressively more favorable environment as ridging balloons aloft over the NW Caribbean and an upper low backs away to the west, illustrated by the GFS Day 7 upper wind forecast. The WNW to ESE orientation of the jet stream to the north over the U.S. will likely allow upper ridging to continue ballooning into the Gulf of Mexico over the disturbance, an environment conducive for tropical development. None of the main global models show significant development of this disturbance, but given the favorable environment it will be moving into, I think it will be a threat to develop in the vicinity of the NE Yucatan Peninsula. The latest runs of the GFS have begun hinting at a tropical storm forming in the Gulf of Mexico, beginning to support this idea. The GFS and CMC ensemble means have also recently begun to show an increasingly wet NW Caribbean in about a week from now, indicating heavy precipitation associated with a strong tropical disturbance.

If a tropical storm does form in the NW Caribbean or southern Gulf of Mexico, its future track will be of obvious interest. The pattern a week from now is forecasted to feature a washed out (stalled) front draped over the southern U.S., evident as deeper blues in this forecast image. The upper trough that brought this front in is likely to stall near the eastern seaboard and leave a weakness over the eastern gulf through which our disturbance could move on a northeastward path towards Florida. However, given the washed out nature of the front with high pressure building behind it, it may be difficult for a disturbance near the Yucatan Peninsula to recurve into Florida. Also, the 500mb pattern for storms near the Yucatan Peninsula that end up hitting east of the Mississippi typically features a strong trough coming down from the Midwest, not a trough that is in the process of leaving the SE US like what is forecasted for next week. Thus, a more likely path to me currently seems to be westward or northwestward into the western Gulf of Mexico towards northern Mexico or southern Texas. However, considerable uncertainty exists, as this forecast is for at least a week from today, and the track of the disturbance may be influenced by whether it even develops into a storm or not. Details about the future of this system in the Gulf of Mexico will be better known in 5-7 days when it is trying to develop in the western Caribbean.

The concept chart below illustrates my overall thoughts for this system next week. I will likely post a video update in a couple of days, especially if the computer models begin to support development of this system.