Rob Lightbown of Crown Weather Services
Monday, May 28, 2012 9:00 am
Some of you may be asking about the area of disturbed weather in the western Caribbean near the Cayman Islands and just west of Jamaica. This disturbed weather is being created mainly by vorticity in the middle levels of the atmosphere and a large amount of divergence (basically large amounts of air expanding out upstairs in the atmosphere).
At this point, development into a tropical cyclone is quite low in the short term as there is little or no low-level convergence and no vorticity or spin near the surface. Additionally, wind shear values across the central and western Caribbean are between 30 and 40 knots which is too hostile for any sort of development.
Later on this week and into this weekend, however, this area of disturbed weather may need to be watched more closely as it is forecast to move into the northwestern Caribbean and the Yucatan Channel where environmental conditions are a little more favorable for development. The NAM model forecasts that an area of low pressure may spin up near the Gulf of Honduras by late Wednesday into Thursday. None of the other model guidance forecast any spin-up low pressure systems in the western Caribbean.
My thinking as of this morning is that the chances for tropical development in the western Caribbean for much of this week is nearly zero. Should this area of disturbed weather persists then this might be something that needs to be watched by this weekend. It should be pointed out that even though the GFS and European model guidance do not develop any sort of low pressure system development, they do keep much of the Caribbean wet and stormy for the next 5 to 7 days and that is the type of persistence you are looking for when dealing with possible tropical development.