Tropical Depression 4 formed last night after a major burst of convection, seen on the satellite image below. This convection, while strong at the time, has weakened and the low level circulation has gradually weakened throughout this morning and early afternoon. Some additional increase in strength is expected but Firsthand Weather does not anticipate that TD Four will become a Tropical Storm at this time.
Regional Conditions in the Tropics
Currently, dry air from an earlier Saharan Air Layer continues to be in place over the Atlantic as seen on the Water Vapor image above. The entrainment of this dry air continues to be the biggest prohibiting factor preventing Tropical Depression 4 from increased development. As Chris had forecast in his previous article, other conditions are currently conducive for tropical development at this time, but wind shear is expected to increase as Tropical Depression 4 moves north of the Lesser Antillies. This will cause the depression to weaken into a Post Tropical Cyclone and dissipate before reaching the coast of the United States.
Tropical Depression 4 Expected Track and Model Analysis
At this time, Tropical Depression 4 is moving West-Northwest around 21 mile per hour. This track is expected to continue for then next couple of days as Tropical Depression 4 moves just north of the Lesser Antillies. 4 should then continue on that general heading until dissipation to the Northeast of the Bahamas.
The latest GFS model, show below, does show some marginal strengthening in the short term, and the forecast calls for maximum sustained winds to reach 35 miles per hour, but beyond the next day or 2, conditions become unfavorable and the Tropical depression quickly comes apart as shown in the second image.
As seen in this second image, the weakening system begins to dissipate while North of Puerto Rico and then completely dissipates in later images.