Disturbed weather continues in the Caribbean

By: Levi32 , 3:52 PM GMT on June 11, 2009

Tropical Tidbit from 12:00pm EDT June 11, 2009:
An upper trough continues to linger over the western Caribbean this morning, producing showers and thunderstorms in the diffluent flow on its east side. This trough is starting to move east, as seen in satellite imagery evidenced by the diffluent zone shifting east over Haiti and extreme eastern Cuba. An area of surface low pressure continues to sit under the southeast flank of the upper trough, enhancing thunderstorms north of Columbia and Panama. This low is getting sheared by the upper trough, and is currently not expected to develop during the next 48 hours.

During the next 2 days the upper trough is expected to lift out of the area, getting replaced by a weaker shortwave that will close off into a cut-off low that will move SW over Mexico and into the east Pacific. The backing away of this upper low will ventilate the western Caribbean and allow a low-shear environment to develop in 72-96 hours. This time-frame may vary depending on the behavior of the upper trough, which is the main point on which the models have been disagreeing.

Meanwhile, the area of low pressure in the southern Caribbean will be drifting slowly northwest as the upper trough gives it room to do so. The models are coming into fair agreement on the evolution of this system. The CMC and NOGAPS depict a weaker system with a northwest track over the southern Yucatan Peninsula and into the western Gulf of Mexico. The GFS has completely dropped the low, but continues to handle the entire situation poorly, and thus I don't really care. The NAM has taken its rightful position as a terrible tropical forecaster and joined the GFS in its poor handling of the situation.

The ECMWF more or less agrees with the CMC and NOGAPS, forecasting a weak low to drift north of Honduras Monday through Wednesday of next week before advecting into the southern Gulf of Mexico under the influence of a deep-layer high over the north gulf coast. This has been my model of choice from the beginning, as it has been the only one properly handling the timing of this feature as the shear gradually relaxes in the western Caribbean.

Development of this low remains uncertain, as factors like land interaction with central America are hard to pinpoint right now. At this point I don't foresee significant development during the time that it will have in the Caribbean, but depending on how it looks in 5 days, it may try to develop in the Gulf of Mexico. Regardless of development, this system will continue to enhance rainfall over Jamaica, Hispaniola, eastern Cuba, and the Bahamas over the next couple days, with amounts of 1-3 inches generally expected. I will continue to monitor this system for any development as it drifts northwestward over the next few days.

Elsewhere in the Alantic....a strong tropical wave along 52W is generating an area of thunderstorms to the east of its axis. This wave has a strong low-level signature on visible satellite imagery and 850mb vorticity maps. The wave is about to enter an area of subsidence due to upper confluence associated with a ridge of high pressure, which should prevent the windward islands from getting much rain as the wave passes tomorrow. This wave is not a threat to develop at this time due to northerly wind shear, but it should be watched down the road in 5-7 days when it enters the western Caribbean, where the environment will be more conducive for development.

We shall see what happens!

West Caribbean Visible Satellite: (click image for loop)

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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3. Levi32
9:51 PM GMT on June 11, 2009
18z GFS continuing to move everything out to the north way too fast before the upper low has a chance to retreat to the SW. On the surface map you can almost see the remnant surface circulation in the southern Caribbean, which is where the low should be on the model, while the surface trough races up near Cuba.

48-hour GFS surface:

48-hour GFS 200mb:

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2. TampaSpin
5:04 PM GMT on June 11, 2009
Good Job!
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About Levi32

Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.

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