Rob Lightbown of Crownweather.com warned on Monday (30) of:

“… a fairly robust tropical wave that is located over the northern Leeward Islands early this afternoon. This system is producing some very squally weather with wind gusts of 60 to 65 mph being reported on Saint Barth a little while ago. This tropical wave is tracking west-northwestward and will likely affect the Virgin Islands as well as Puerto Rico by later this afternoon and especially tonight. Those of you in Puerto Rico and the Virgin Islands, be ready for locally heavy rainfall and strong winds with gusts to 60 mph possible. This disturbance will then likely affect the Dominican Republic and Haiti once we get into Tuesday. As for development chances: They are very low as the combination of land interaction and strong wind shear will prevent any sort of development. Given that, the very squally weather that is expected will sure make it feel like tropical storm conditions across the Virgin Islands and Puerto Rico by late this afternoon and tonight.

“Now, I am closely watching an area of disturbed weather, designated Invest 99L by the National Hurricane Center, located about 900 miles to the southwest of the Cape Verde Islands. Satellite imagery this afternoon showed some fairly disorganized shower/thunderstorm activity, however, it seems that the convection is very slowly increasing and this is a system that will need to be watched over the next few days. Why is that? Because wind shear values are forecast to remain light enough and the atmosphere is forecast to be moist enough to allow for development to occur. Additionally, the track of Invest 99L potentially brings it into the southern Leeward Islands and the northern Windward Islands, as well as across Barbados by very late Friday or during Saturday.

“The latest model guidance points to a slightly north of due west track this week with the GFS model forecasting modest intensification to perhaps a tropical storm while the European model forecasts very little development. The Canadian model seems to be the most aggressive forecasting 99L to intensify into a hurricane by Thursday into Friday and turn northwestward raking much of the Leeward Islands with hurricane conditions by Friday night and Saturday and then tracking towards the southeastern Bahamas by Sunday.

“It is of my opinion that the Canadian model is too aggressive with the intensification while the European model is not aggressive enough given the favorable environmental conditions ahead of 99L over the next few days. My thinking right now is for slow development and intensification to Tropical Storm strength by as early as Friday. I do think that the southern Leeward Islands, the northern Windward Islands and Barbados will be first-in-line for future Tropical Storm Ernesto with tropical storm conditions possible as early as Friday afternoon across these areas.

“Now, beyond the Leeward and Windward Islands, I think that the ridge of high pressure will be strong enough to keep Ernesto to be on a west-northwest track into the Caribbean by Sunday and Monday. Should the European model be correct and this system does not develop at all, then a eventual track into Central America could occur in about 10 days from now. Now, if Invest 99L does develop slowly and steadily, then a more northwesterly track towards Puerto Rico, Haiti and the Dominican Republic could materialize by next week.

“So, as I have already mentioned, I think a slow, but steady intensification seems most probable with 99L possibly becoming a tropical depression by Wednesday or early Thursday and then possibly a tropical storm by Friday with tropical storm conditions possible across Barbados, the southern Leeward Islands and the Windward Islands as early as Friday afternoon.

“Needless to say, I am monitoring Invest 99L very closely and I will keep you all updated on the latest.”

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