Watching three tropical waves

Heavy thunderstorms continue over the waters east of Florida this morning along an old cold front. Wind shear is 10-15 knots in a narrow band along this old front, which is low enough to allow some development to occur. A non-tropical area of low pressure developed yesterday near 28N 74W, a few hundred miles east of Cape Canaveral, Florida. Preliminary forecast tracks for this low are plotted in Figure 1. However, visible satellite imagery from this morning reveals that a new area of low pressure is developing much closer to the Florida coast near 27.5N 78W, about 150 miles east of Vero Beach. Long range radar out of Melbourne is also showing an increase in thunderstorm activity off the coast in association with this developing low. This low is drifting slowly southwards, and we don't have any premilinary model tracks from NHC for it. My guess is that this new low will dominate the circulation and the old low NHC has been tracking will dissipate later today. The East Coast of Florida near Vero Beach and West Palm Beach could get heavy rain today as this new low continues to develop.

Development along old fronts is usually slow, so the earliest we should expect a tropical depression to form from either of these two lows is Tuesday. There is a significant amount of wind shear on either side, plus plenty of dry air to the north, so anything that develops will likely struggle to intensify. The Hurricane Hunters are scheduled to investigate this system on Tuesday afternoon.

The computer models are forecasting that any low that forms along the old front will begin moving northwestwards towards the Carolinas over the next three days, in response to a trough of low pressure swinging across the eastern U.S. When the trough moves out to sea on Thursday, high pressure is forecast to build back in, forcing the system back towards the west, or leaving it nearly stationary off the East Coast. None of the computer models forecast that the storm will grow to anything stronger than a 45-mph tropical storm.


Figure 1. Current satellite of the Florida region.


Figure 2. Preliminary models tracks for the East Coast disturbance.

Tropical wave in the eastern Caribbean
A tropical wave a few hundred miles west of the Lesser Antilles Islands is moving west-northwestward at 10-15 mph. While the wave is an area of low wind shear (5-10 knots), it is embedded in a large area of dry air, which is keeping thunderstorm activity minimal. A QuikSCAT pass from 5:48am EDT today showed no surface circulation and top winds below 20 mph. The dry air should keep any development slow today. Wind shear is expected to remain below 10 knots near the wave's location through Tuesday, but the long-term prospect of this system becoming a hurricane is very low. The wave is headed for the Western Caribbean, where high wind shear associated with an upper-level low pressure system will dominate all week. The Hurricane Hunters mission scheduled for today was canceled, due to the wave's lack of organization. NHC did not run their package of preliminary model tracks on it this morning, and this may be the last mention I give of this system.

New wave off of Africa
A large and impressive tropical wave has moved off the coast of Africa today, a few hundred miles southeast of the Cape Verdes Islands. The wave has a well-defined circulation at mid-levels, and is under about 10 knots of wind shear. It could develop into a tropical depression in the next few days as it moves west-northwest just south of the Cape Verdes Islands.

Figure 3. Preliminary models tracks for the Cape Verdes Islands disturbance.

I'll be back with an update Tuesday, unless some significant development occurs. On either Tuesday or Wednesday, I plan to post my outlook for the remainder of August. Is today's activity a sign the tropics are heating up?

Jeff Masters