Tropical weather analysis - July 30, 2012
Invest 99L
After a month of nary a single invest, one has finally been declared this morning in the eastern Atlantic, in association with a tropical wave. This wave, centered about 750 miles southwest of the Cape Verde Islands, is showing signs of organization. The shower activity is displaced west of the wave axis due to easterly shear.
Figure 1. Latest infrared satellite image of Invest 99L. Image credit: NOAA
The SHIPS brings the system to just under hurricane strength early Saturday morning. The current shear is expected to abate; however, I note that the thermodynamics do not look all that favorable. The global models respond to this with differing solutions. The ECMWF does not develop it and eventually shoots it westward into Central America as it follows the lower-tropospheric flow. The CMC is the fastest in calling for a full-fledged tropical cyclone in about 72 hours. The GFS projects a more delicate balance and slowly develops the system through the weekend. I prefer the GFS solution given the unfavorable thermodynamics, and the system's relatively low latitude. Also, given the fairly large wind field with the system, entrainment of dry air into the circulation as the low attempts to consolidate is distinctly possible.
Water vapor imagery depicts a large upper low near 26N 41W dropping southward toward 99L. All of the models initialized this feature and do not show appreciable interaction between the two systems. However, this vortex appears to be fairly strong above 500 mb, so 99L develops quicker than anticipated, it would likely move more toward the west-northwest and potentially miss the Lesser Antilles. This is the solution favored by the CMC. Again, given the subsidence lying in the path of the system, this seems unlikely for now. The models also have differing thoughts on the synoptic pattern at longer ranges. The GFS and ECMWF generally show a stronger and westward-expanding ridge, while the CMC prefers to linger a trough along the eastern seaboard. I am not going to waste time hypothesizing how things will evolve. Right now all we have is a tropical wave worth monitoring, and we should leave it at that pending future developments in either direction.
But I will say that given the system's low latitude, and the fact that it should remain relatively weak for the next few days, prompts me to prefer a system that tracks through the Caribbean and eventually into the Gulf of Mexico. I'm not particularly comfortable with even saying that much though, but that is the sort of track I see in my crystal ball should the system consolidate in the area it's in now.
Probability of development in 48 hours: 20%
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