Active tropics today

A disturbance ("94L") in the Gulf of Mexico has not gotten better organized today and has just about run out of time. Long range radar out of New Orleans shows the advance rain showers from 94L are already at the coast, and there are no signs of spiral banding, rotation, or organization in either the radar imagery or satellite loops of 94L. Wind shear has increased to 10-20 knots over the Gulf of Mexico, and it now appears unlikely 94L will be able to develop into a tropical depression.

Lesser Antilles disturbance 97L
Of greater concern is a tropical wave (97L) about 300 miles east of Barbados in the Lesser Antilles Islands. This wave has not gotten any better organized during the past 12 hours, as seen in the latest Satellite imagery. The wave is under about 10 knots of wind shear. The shear is forecast to remain below 10 knots through Tuesday, and there is some favorable anticyclonic outflow at high levels, and 97L has a good chance of developing into a tropical depression by Tuesday. At that point, the future evolution of the storm depends strongly on how far north it is. If 97L moves northwest over Puerto Rico on Wednesday, as the GFDL and some of the global models predict, it may encounter a zone of high wind shear associated with the bottom part of a trough of low pressure positioned to the north of Puerto Rico. This shear should keep the storm from becoming a hurricane. If 97L stays on a more west-northwest track and penetrates into the Caribbean Sea south of Puerto Rico, as predicted by the simpler BAMM model, the storm is likely to encounter less shear, and could grow into a hurricane. Regardless, 97L will bring heavy rain and gusty winds to most of the Lesser Antilles Islands tonight through Tuesday.

Links to follow for 97L
Martinique radar
Barbados weather
Guadaloupe weather
Martinique weather
St. Lucia weather


Figure 1. Microwave image from 4:46 pm EDT today showing low-level spiral bands starting to form on the west side of 96L. Image credit: Navy/NRL.

Far Atlantic disturbance 96L
A tropical wave "96L" in the far eastern Atlantic, about 650 miles southwest of the Cape Verdes Islands, has gotten more organized during the past 24 hours, as seen in the latest Satellite imagery. The circulation associated with the wave is unusually large. The storm will be a little slow to get going, since the storm is so far south. At the storm's current latitude--6 degrees north of the Equator--it cannot leverage the earth's spin very much to help spin up the huge circulation it has. Despite it's close proximity to the Equator, low-level spiral bands have already formed, as seen in recent microwave satellite images (Figure 1). The wave is under about 10 knots of wind shear. The shear is forecast to remain below 10 knots through Wednesday, and there is some favorable anticyclonic outflow at high levels. There is a good chance 96L will become a hurricane late this week, as forecast by the SHIPS intensity model. The Lesser Antilles Islands should anticipate the possibility that this will be a hurricane by the time it reaches the islands seven days from now, although it could miss to the north. It is possible 96L will encounter a zone of high wind shear beginning four days from now. The HWRF model develops 96L into a 55-mph tropical storm by Tuesday, then weakens the system the remainder of the week. The GFDL model does not develop 96L at all.

I'll edit this blog tonight to include the evening QuikSCAT pass, if it hits 96L. Otherwise, I'll be back Monday morning--and maybe I'll even talk about our one active storm, Jerry!

Jeff Masters