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 , 4:16 PM GMT on September 25, 2011
Tropical Storm Ophelia is barely alive today, as high wind shear and dry air continue to take their toll on the storm. Satellite imagery shows that Ophelia has an oval, highly-stretched center of circulation, with almost no heavy thunderstorm activity near the center. Most of the storm's heavy thunderstorms are to the east of the center, with just a few puffs of thunderstorms occasionally popping up near the center. An analysis from the University of Wisconsin CIMMS group shows a high 25 - 30 knots of wind shear due to strong upper-level southwesterly winds. Water vapor satellite images show Ophelia is at the eastern edge of large area of very dry air.
Figure 1. Noon satellite image of Ophelia. It's tough to pick out a low-level center, and all of the storm's heavy thunderstorms lie several hundred miles to the east of the center. Ophelia is barely alive.
Forecast for Ophelia
The latest SHIPS model forecast predicts wind shear will drop to the moderate range, 15 - 20 knots, tonight through Tuesday morning. If Ophelia survives until tonight, the lower shear should allow the storm to make a bit of a comeback. Bermuda is the only land area that might be threatened by Ophelia, but it remains questionable whether or not Ophelia will still be a tropical storm when it makes its closest pass by Bermuda late in the week.
Philippe forms in the far eastern Atlantic
Tropical Storm Philippe formed in the far eastern Atlantic off the coast of Africa yesterday. 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 chance to become the season's fourth hurricane; the 11 am EDT NHC wind probability forecast gives Philippe a 45% chance of intensifying into a hurricane by Tuesday morning. Philippe is headed northwest and then north towards cooler waters, and is not a threat to any land areas.
Figure 2. MODIS satellite image of Hurricane Hilary at 1:40 pm EDT September 24, 2011. At the time, Hilary was a Category 4 storm with 140 mph winds. Image credit: NASA.
Eastern Pacific's Hurricane Hilary weakens to Category 3 strength
In the Eastern Pacific, Hurricane Hilary weakened slightly to a Category 3 hurricane with 125 mph winds. Hilary is headed west, away from Mexico, and the storm is small enough that its outer bands are not causing flooding problems for Mexico. A trough of low pressure expected to move over the Western U.S. by the middle of the week should be strong enough to turn Hilary to the north, eventually bringing Hilary to Mexico's Baja Peninsula. The timing of when Hilary might hit Baja is highly uncertain, though. The ECMWF model keeps Hilary offshore for the next 7 days, while the latest 06Z runs of the GFS and NOGAPS models predict Hilary could hit Central Baja on Friday.
Dangerous Typhoon Nesat headed for the Philippines
What may be the season's most dangerous storm in the Western Pacific, Typhoon Nesat, is headed west at 10 mph towards Luzon Island in the Philippines. Nesat is just a Category 1 typhoon with 80 mph winds, but has favorable conditions for intensification. Shear is a moderate 10 - 15 knots, Nesat is embedded in a very moist environment, has very warm sea surface temperatures of 30°C under it, and a very favorable upper-level outflow pattern above it. Nesat has plenty of time to intensify into a major Category 3 or 4 typhoon before its expected landfall on Luzon Island in the Philippines near 9 am local time Tuesday morning.
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