Summary- Where is it now: Tropical Atlantic, along 43W
- Where will it be: Lesser Antilles by Tuesday the 18th, central Caribbean on Thursday the 20th, western Caribbean by Saturday the 22nd.
- Model support: Minimal from the GEFS. A few weak members from EPS. Some support from GEFS-Parallel and GEPS members but location varies considerably. Keep an eye on the deterministic models, but the ensembles are probably more worth your time for general development chances given the uncertainties.
- What to watch for: Environmental conditions over the Caribbean and the possibility that the currently muted wave may gain convection and vorticity as it moves into the Caribbean
It's currently devoid of convection and takes up an assuming presence in the wake of Tropical Storm Josephine, but it definitely has potential. Right now, the wave's associated moisture pouch is rather low in amplitude, with most of the moisture remaining south of 15N (by comparison, a more
lucrative wave over Africa is pushing its moisture up to beyond 20N).
As we begin to move towards peak season, it's worth monitoring each tropical wave on their two-week treks across the Atlantic. If this particular tropical wave is able to generate some deep vorticity-generating convection on approach to the Lesser Antilles, then the wave can increase in amplitude and develop into a more stout presence in the eastern Caribbean. The GEM shows this sort of evolution,
generating a pocket of vorticity in about a day's time that allows the wave to eventually crest as it moves across the Caribbean. Tropical cyclogenesis would be favored in that case (the GEM does have a TC after that point, but this is rather far out and the fine details shouldn't really be the focus at this range).
This is just one scenario; alternatively, if conditions are unsupportive of convection, then the wave may remain low in amplitude and fail to gain the requisite vorticity in the Caribbean to kickstart future development (i.e. the
GFS). In either case, it appears that wave amplification on approach and through the Lesser Antilles seems to be the thing to watch for this wave if it is to develop in the Caribbean, though the lack of such amplification does not preclude possible development further west in the Bay of Campeche, western Gulf, or eastern Pacific.
The wave's trek across the Caribbean coincides with the
approach of strong upper-level divergence moving into the western Atlantic. As has been discussed on the seasonal indicators thread, the
mid- to long-range synoptic patterns favor westward tracks through the Caribbean and the possibility of northward curvatures in the Gulf as a result of enhanced ridging over the Bahamas/Greater Antilles region (the Sargasso Sea). This is noted on both the
GEFS and
GEFS-Para, for instance, which juxtapose westward extending ridging with a strong trough over the Eastern US. Setups like these favor pronounced poleward outflow jets (between the trough and ridge) and upper-level anticyclones to feed that poleward jet, so it is no surprise that some of the ensemble guidance shows a
broad upper-level anticyclone spanning much of the Caribbean. If the tropical wave over the central Atlantic develops, it could make use of this environment within the Caribbean depending on its alignment with the anticyclone. We'll also need to watch for how moist the Caribbean gets over the next week. As for sea surface temperatures, well, I think
this puts it rather succinctly.
589KB. Composite of infrared satellite and total precipitable water (from RealEarth) and the NHC Tropical Surface Analysis
