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 , 13:38 GMT le 08 octobre 2009
Tropical Depression Henri continues to suffer from high wind shear of 20 knots, and appears on its way to dissipation. Visible satellite loops show that the shear has exposed Henri's low level center to view, and this center has become less circular and not as well defined. Henri's heavy thunderstorms have been shrinking in areal coverage and intensity, and are displaced from the center--signs of a highly sheared tropical storm that has little time left to live.
All of the reliable global computer models show weakening and dissipation of Henri by Friday, due to high wind shear. Wind shear in the vicinity of Henri's remains is predicted to fall to the moderate range by Saturday, but at that time it appears that the storm will be moving over the Dominican Republic, which will disrupt whatever is left of the storm's circulation. Henri's remains may bring heavy rains of 2 - 4 inches the the Dominican Republic and Haiti Saturday through Monday. By Tuesday, the remains of Henri will likely be moving across Florida and/or Cuba and into the Gulf of Mexico, where we will need to watch the system for re-development.
Figure 1. Morning satellite image of Henri (top) and a new tropical wave we're watching (bottom). The tropical wave south of Henri, just off the coast of South America, has become disorganized.
Tropical wave south of Henri
A tropical wave south of Henri, just north of the coast of South America and a few hundred miles east-southeast of the southernmost Lesser Antilles Islands, has grown less organized since yesterday. Both the areal coverage and intensity of the heavy thunderstorm activity has decreased, and there are no signs of organization to the cloud pattern. This wave is under about 10 knots of wind shear, but is too close to the Equator to be able to take advantage of the Earth's spin to help it spin up into a tropical depression very quickly. Also, the wave may pull in some dry, stable air from South America as it scoots just north of the coast over the next few days. NHC is giving this disturbance a low (less than 30% chance) or developing into a tropical depression by Saturday. There are no computer models showing development of this system.
Figure 2. Tropical Storm Parma (left) and Typhoon Melor (right) on October 7, 2009. At the time, Melor was a Category 4 typhoon with 135 mph winds, and Parma was a tropical storm with 60 mph winds. The two storms were close enough together that they rotated around a common center counter-clockwise, in an interaction known as the Fujiwara Effect. This forced Parma to reverse course and pass over the Philippines from west to east, after the storm had already crossed the islands from east to west. Now that Melor is gone, Parma is crossing the Philippines once more from east to west. Image credit: NASA Earth Observatory.
Typhoon Melor made landfall yesterday on Japan's Honshu Island south of Osaka as a Category 1 typhoon with 85 mph winds. The typhoon killed two people and caused some moderate damage to the coastal region of southern Japan where it came ashore.
In the Philippines, Tropical Depression Parma is making its third traverse over the Philippines' Luzon Island. is expected to dump up to six more inches of rain today over the already sodden portions of northern Luzon. The storm is being blamed for 22 deaths and millions in agricultural damage.
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