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 , 26. syyskuuta 2011 klo 12:07 (GMT)
High wind shear and dry air finally managed to kill off Tropical Storm Ophelia yesterday. The storm's remnants continue to fester a few hundred miles east of the Northern Lesser Antilles Islands, but dry air and moderate wind shear of 10 - 20 knots should make any regeneration of Ophelia slow. NHC gave Ophelia a 20% chance of regenerating by Wednesday in their 8 am Tropical Weather Outlook. In the far eastern Atlantic, Tropical Storm Philippe is headed west-northwest into the middle of the North Atlantic, and is not expected to trouble any land areas. Philippe is the 16th named storm this year, tying 2011 with 2008, 2003, and 1936 for 7th place for the most number of named storms in a year. Philippe's formation date of September 24 puts 2011 in 2nd place for earliest date of arrival of the season's 16th storm. Only 2005 had an earlier 16th storm. With only three of this year's sixteen storms reaching hurricane strength so far, though, this year has been near average for destructive potential. Atlantic hurricane records go back to 1851. Philippe has a modest chance to become the season's fourth hurricane; the 5 am EDT NHC wind probability forecast gave Philippe a 23% chance of intensifying into a hurricane by Tuesday afternoon. Wind shear is expected to steadily increase today to 15 - 20 knots, limiting Philippe's chances to become a hurricane.
Figure 1. MODIS satellite image of Hurricane Hilary at 2:25 pm EDT September 25, 2011. At the time, Hilary was a Category 3 storm with 125 mph winds. Image credit: NASA.
Eastern Pacific's Hurricane Hilary slowly weakening
In the Eastern Pacific, Hurricane Hilary has slowly weakened to a Category 3 hurricane with 120 mph winds. A trough of low pressure is expected to turn Hilary to sharply to the north on Wednesday, but most of the models do not bring Hilary ashore over Mexico's Baja Peninsula during the next five days. Since Hilary will be crossing cool water and encountering increased wind shear on its journey north, the storm is likely to be no stronger than a tropical depression if it does manage to reach the coast.
Figure 2. Microwave image from NASA's TRMM satellite showing the estimated rain rate of Typhoon Nesat at 4:56 am EDT Monday September 26, 2007. Rainfall rates of up to 0.8"/hour (yellow colors) were occurring along the southeast quadrant of the eyewall. Image credit: Navy Research Lab, Monterey.
Typhoon Nesat nears landfall in the Philippines
Typhoon Nesat, a Category 1 typhoon with 90 mph winds, is just a few hours from landfall near Casiguran on Luzon Island in the Philippines. Nesat was expected to intensify to a major Category 3 storm before landfall, but the typhoon ingested a large pulse of dry air that got wrapped into the core of the storm, slowing down intensification. The typhoon still has time to intensify into a Category 2 storm, but Nesat's wind and storm surge will not cause major devastation. Heavy rains from Nesat are a major concern, though. Recent microwave satellite images (Figure 2) show rains up to 0.8" per hour falling along the southeast quadrant of Nesat's center, and heavy rains of 5 - 10 inches will cause significant flooding in the Philippines. Nesat will lose strength during its crossing of the Philippines, but is expected to regain strength as it crosses the South China Sea before making another landfall near China's Hainan Island on Thursday.
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