Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 4:34 PM GMT on October 05, 2005
Return of Stan
A large area of thunderstorms broke off from Stan this morning, and has emerged into the Yucatan Channel. Satellite imagery this morning has shown some improved organization of this feature, and with wind shear 10 knots over it, there is a chance of a tropical depression or tropical storm forming later today or tomorrow as the system tracks north-northeast towards western Florida. If this system were to be named, it would get the new name Vince, and not Stan, since the primary circulation of that storm pushed into the Pacific Ocean this morning.
Winds at the NOAA buoy 42056 at 20N 85W in the Yucatan Channel just switched from easterly to westerly at 11 am EDT today, suggesting that a closed circulation has already formed. Winds at this buoy were 25 mph gusting to 34 mph, and wind estimates from the latest QuikSCAT satellite pass were as high as 45 mph in this region. Regardless of whether or not this system develops into a tropical storm, southwest Florida can expect tropical storm conditions Thursday afternoon when this system comes ashore. The system will continue to the northeast and drench the areas already dumped on by Tropical Storm Tammy, and the entire East Coast needs to be concerned about serious flooding problems from this one-two punch.
I'll update this blog by 4pm today. The remainder of this morning's blog appears below, unchanged.
Figure 1. BAMM model track for tropical disturbance off of the Yucatan.
Tropical Storm Tammy formed 20 miles offshore from Cape Canaveral this morning. With 19 named storms, the Hurricane Season of 2005 has now tied 1995 as the second busiest ever. Only 1933, with 21 storms, has had more.
Tammy formed in the presence of some unusually high wind shear from an upper-level low pressure system in the Gulf of Mexico--about 15 - 20 knots--which is decreasing enough this morning to allow some intensification. Radar animations out of Melbourne, Florida, show an intense area of thunderstorms, well offshore, that are increasing in echo intensity. No ships or buoys have actually measured tropical storm-force sustained winds of 40 mph yet, but it is likely that such winds are occurring in the most intense convection to the east of the center. Infrared satellite images confirm that this area is growing in size and intensity, and some very cold cloud tops are now appearing. As long as the center remains offshore, Tammy may continue to intensify. Intensification into a hurricane is not expected, and would be a major surprise, due to the high wind shear. It is more likely that the center will move onshore tonight as a weak tropical storm with maximum winds in the 40 - 50 mph range. In any case, the primary threat from Tammy will be from her rains. Bands of heavy rain will move onshore the coasts of northern Florida, Georgia, and the Carolinas over the next few days, creating flooding problems, particulary in Georgia, where the precipitation will be heaviest and the soil is moister.
Figure 2. Mild drought conditions cover South Carolina, which will slow flooding in that state. Flooding is more likely to be a problem in Georgia and perhaps North Carolina, where the soil is moister.
Tammy is being drawn northward by a trough and its associated cold front that are expected to arrive over the East Coast on Friday. The remains of Tammy will track up the front, drenching the entire East Coast, and it is likely that at least one more area of low pressure--probably not a tropical storm, but it could be--will develop along the front late in the week and move northeast, giving the entire East Coast additional heavy rain.
Stan dissipated this morning over the Mexican mountains, and his circulation is pushing onward into the Pacific Ocean, where a new tropical storm may form. Little enough of Stan remains in the southern Gulf of Mexico to allow a new tropical storm to form there later in the week, although the NOGAPS model is still calling for that to happen.
Stan's onshore winds blowing across the Pacific Ocean into his center caused a major disaster in El Salvador, Guatemala, Honduras, Nicaragua, and Mexico. In Mexico's southernmost state of Chiapas, a river overflowed its banks and tore through the city of Tapachula, destroying numerous houses. Guatemala is reporting four dead, Nicaragua nine dead, and 49 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 will still generate rain over the area for two more days.
Elsewhere in the tropics
The area of disturbed weather near Puerto Rico has diminished, and tropical storm formation is not expected here or anywhere else in the Atlantic through Thursday.
I'll have an update about 3pm today when the Hurricane Hunters arrive at the storm.
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