Late on Sunday afternoon, a weak surface low pressure system associated with an area of disturbed weather across the southern Lesser Antilles became better organized and became the season's 27th depression, Tropical Depression 27, at 10p Sunday night. Convection associated with the system is displaced to the east of the center of circulation due to the impacts of upper-level shear associated with a deep mid-latitude trough centered to the north of the system. Recent satellite images and radar imagery from Martinique (available at http://www.meteo.fr/temps/domtom/antilles/pack-public/animation/animMOSAIC2.html; unfortunately, the depression is moving out of radar range as of early Monday morning) do suggest that the system is becoming better defined, however, and has a shot at becoming a tropical storm sometime on Monday. If the depression were to be named, it would be the season's 24th tropical storm and would have the name Gamma.
Currently, upper-level winds are only marginal for development due to the aforementioned upper-level trough to the north of the system. However, over the next couple of days, this trough is expected to lift out, leaving the depression to the south of an upper-level ridge of high pressure across much of the SW Atlantic Ocean, providing favorable conditions for strengthening. Furthermore, oceanic heat content & temperatures across the Caribbean are more than sufficient for development. Assuming the depression survives the next day or so, it should have every opportunity to become a hurricane in the 3-5 day time frame. We've seen many storms thus far this season survive modest shear and I don't expect this one to be any different. Mid-level shear and dry air intrusions from the ridge to the north may serve to keep intensity in check to a small degree, though I still believe the forecast is on the conservative side through 5 days.
Over the next few days, underneath the influence of the trough and, later, the ridge to the north, the depression should gradually move toward the northwest and then west through the next 3-4 days. The track through 4 days looks pretty good from my end. The trough currently over the eastern US will likely pass well to the north of the depression -- along the northern extent of the upper ridge -- and have little to no impact on the track or intensity of the system. However, a strong trough of low pressure currently moving into the northwestern US will be moving into the eastern US in the 3-4 day time frame and off the coast shortly thereafter. As the depression moves into the western Caribbean toward the middle to end of the workweek, it should begin to feel the influence of this trough -- particularly if the depression is as strong as forecast.
A lot is still up in the air depending upon timing and intensity of both the depression and the trough, but the potential is there for yet another US impact from a tropical cyclone heading toward the weekend. The most likely target area is the eastern Gulf, but no area can be ruled out -- including a continued westward track into Central America if the depression moves faster than anticipated or the trough does not capture the system. However, at this point, I feel a path toward the northwest Caribbean with a gradual turn toward the north is the most likely scenario. As a result, I believe the 5 day position may be a little too far to the south...albeit not to a large degree.
Those across the entire Caribbean and eastern Gulf -- say, east of New Orleans -- should pay close attention to this developing system over the course of the week.
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