Florida gets soaked; Stan a major disaster in Central America

Tropical disturbance approaching Florida
The leading portion of the tropical disturbance over the central Bahama Islands has moved ashore in Central Florida today, bringing rains of up to three inches and wind gusts of 40 mph along the coast. Although the disturbance is not a threat to develop into a tropical depression today, the impact on Florida will be similar to that of a tropical depression--sustained winds of 30 mph, with gusts to 45 mph along the coast, along with 3 - 6 inches of rain and large battering waves. The disturbance currently has a weak surface circulation center just south of Andros Island. The shear over the storm is high, 10 - 20 knots, and development into a tropical depression is not possible until Wednesday or Thursday, when the shear may drop below 10 knots. However, the disturbance will be near or over the Florida Peninsula when that happens, limiting the chances for development. I believe that this system will not develop into a tropical depression at all. Instead, the disturbance will interact with an upper-level low pressure system and cold front on Thursday, and become a large--and very wet--ordinary low pressure system. This low will pump copious amounts of tropical moisture into Florida, Georgia, and the Carolinas over the next three days. By Thursday, a cold front swings onto the East Coast, and several areas of low pressure--all non-tropical--are expected to develop along the front Thursday through Saturday and move northeast, giving the entire East Coast drenching tropical rains.


Figure 1.Storm total rainfall from the Melbourne radar.

I speculated about the possibility yesterday of a tropical storm forming near the Carolinas and moving northwards along the coast. This is no longer expected, due to the high wind shear over the region.


Figure 1. BAMM and GFDL model forecast tracks of Bahamas tropical disturbance. The intensity forecast numbers from the SHIPS model are far too high; this system will be lucky to develop into a tropical depression.

Tropical Storm Stan
Stan stormed ashore on the coast of Mexico this morning as a Category 1 hurricane with 80 mph winds, and is expected to finally dissipate Wednesday morning over the Mexican mountains. The onshore winds blowing across the Pacific Ocean into the center of Stan have caused a major disaster in El Salvador, Guatemala, Honduras, Nicaragua, and Mexico. Guatemala is reporting four dead and many communities cut off by rising rivers, and 38 have been killed in El Salvador by mud slides triggered by heavy rains. The death toll will undoubtedly rise much higher. Since Stan's remains are going nowhere fast, as much as 20 inches of rain could fall over the next few days over the mountainous regions of these countries.

Stan's remains may re-organize and form of a new tropical storm over the Pacific, which could move northwest and threaten Baja later in the week. The NOGAPS and GFDL models predict that Stan's remains will linger over the Gulf of Mexico long enough to result in the formation of a new tropical storm there by the weekend. All this will depend on Stan's track; it is very unlikely we would get a new storm in both ocean basins.

Elsewhere in the tropics
Clouds from the tropical disturbance over the Bahamas extend southeastward to Puerto Rico and the Lesser Antilles Islands. The area of disturbed weather near Puerto Rico bears watching, as wind shear values here are 5 - 10 knots, the lowest of anywhere in this disturbance.

The region between Africa and the Lesser Antilles is quiet.

Jeff Masters