Fay slowly winding down; Caribbean disturbance 94L slowly winding up

Tropical Depression Fay has made the fatal mistake of heading inland, away from its oceanic source of sustenance, and now has little hope of reaching tropical storm strength again. Satellite loops show that Fay still has a large circulation covering most of the Southeast U.S., and it will take 2-3 days for the huge amount of angular momentum energy stored in such a large vortex to dissipate as the storm slowly spins down. No models are calling for Fay's center to emerge over water again, and it appears that "The Joker" is finally finished.

Fay's rains
Fay's rains continue to pile up over the Southeast (Figure 1). In Florida, Fay has dumped up to 25 inches of rain over the Melbourne area, 19 inches in Tallahassee, and 14 inches in Jacksonville. In Alabama, rainfall amounts up to seven inches have fallen, with up to eight inches in Georgia (Valdosta) and four inches in Mississippi (Jackson). Additional rains of 4-8 inches are likely over Louisiana, Mississippi, Alabama, Georgia, and the Florida Panhandle over the next 2-3 days.


Figure 1. Total rainfall for the seven days ending Sunday, August 24, at 8 am EDT. Image credit: National Weather Service.

On the plus side, Fay's rains are now moving into some of the most drought-stricken regions of the country--northern Alabama and northern Georgia. In fact, there is now concern about flooding in these regions later this week, if the remains of Fay continue to linger and bring eight or more inches of rain (Figure 2). Fay's rains have now increased the level of Lake Okeechobee by two feet. The lake level stands at 13.11 feet, which is still about 2 feet below normal.


Figure 1. Total forecast rainfall for the five days beginning at 8 am EDT Sunday August 24. Image credit: National Weather Service.

Disturbance 94L in the eastern Caribbean
Heavy thunderstorms associated with a tropical wave (94L) near 12N, 65W, in the eastern Caribbean, have grown more widespread over the past day. This morning's QuikSCAT pass missed 94L, but did show sustained winds of 40 mph north of the center. Visible satellite loops show evidence of rotation in the clouds at middle levels of the atmosphere, but no surface circulation as yet. The area covered by the heaviest thunderstorms is relatively modest. The storm has moistened its environment considerably, and dry air should be less and less of a problem for the storm over the next few days. Wind shear has fallen to a modest 10 knots over 94L and is decreasing. NHC is giving this system a medium (20%-50% chance) of developing into a tropical depression by Tuesday afternoon, and has scheduled a Hurricane Hunter flight to investigate on Monday afternoon.

The forecast for 94L
The models have had a tough time properly handling 94L, and have not been making believable forecasts of the storm's track and speed. The latest (8 am EDT Sunday) GFDL forecast appears to have the most believable forecast I've seen, developing 94L into a tropical storm that tracks over extreme Southwest Haiti, then into the region between Jamaica and Cuba. The NOGAPS and ECMWF models have also been developing 94L with each run the past few days. Heavy rain and high winds from 94L's circulation should affect Haiti's southern Peninsula on Tuesday morning, and spread to Jamaica and eastern Cuba by Tuesday night. The wind shear forecast for the Caribbean calls for very low values of wind shear around 5 knots for most of the coming week. Residents of Haiti, Jamaica, and Cuba should keep a careful eye on this potentially dangerous disturbance. I expect 94L will be a tropical depression by Tuesday, and will eventually grow into a tropical storm or hurricane that will threaten Cuba, the U.S., and/or the Bahama Islands late this week.

Links to follow
Aruba radar

Disturbance 95L in the middle Atlantic
Another tropical wave (95L), near 22N 55W, in the middle Atlantic Ocean, remains disorganized. Wind shear has increased to a marginal 15 knots over 95L, and is forecast to increase further in coming days, ranging between 15-25 knots over the next five days. Visible satellite loops show only a small amount of heavy thunderstorm activity, and 95L is battling a large amount of dry air that surrounds the storm and is interfering with development. NHC is giving 95L a low (<20% chance) of developing into a tropical depression by Tuesday. Several of the models do develop 95L late this week, and Bermuda should keep an eye on 95L. However, I doubt 95L will ever develop into a tropical depression.

Elsewhere in the tropics
Several of the computer models forecast that a tropical wave that is moving off the coast of Africa today will develop late this week.

My next blog will be Monday morning.

Jeff Masters