The area of convection that has been percolating within the Caribbean has acquired sufficient organization and speed to be named Tropical Storm Rafael (at 2100 UTC on 4 November, near the end of the animation, above, created at the CSPP Geosphere site). The storm is approaching the island of Jamaica where Tropical Storm Warnings are in effect.

Rafael is currently in a region of warm sea-surface temperatures and low shear (imagery below is taken from SSEC/CIMSS’s tropical weather website), and slow strengthening is forecast as it moves between Jamaica and the Caymans en route to western Cuba.

The area of rich moisture that is supporting Rafael’s convection has been over the western Caribbean since late October. The animation for November of TPW from the MIMIC site (online archive) is shown below. Note, however, the relative dryness over the Gulf of Mexico, where Rafael is forecast to be by week’s end. The storm would have to overcome a significant amount of dryness to remain intense.

Advanced Clear-Sky Processor for Ocean (ACSPO) Sea Surface Temperatures from VIIRS, below, shown with I05 (11.45 µm) data (NOAA-20 data were downloaded at the CIMSS Direct Broadcast site and processed with CSPP software). Note the lack of convection over the Gulf of Mexico, and the water temperatures. Red in the SST enhancement below is approximately 80^oF. Shelf waters are relatively cool.

GOES-East airmass RGB imagery, below, shows Rafael developing within a moist airmass — that is, a green region within the RGB. As it moves northwestward, however, the environment becomes less favorable; this is indicated by regions with more orange. (Here is a Quick Guide on airmass RGB; here is another one)

More information on Rafael is available from the National Hurricane Center. Interests in the northwest Caribbean and in the Gulf of Mexico should monitor the progress of this storm.

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