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 , 2:22 PM GMT on September 27, 2006
Typhoon Xangsane, potentially the most dangerous tropical cyclone to affect the world this year, is battering the Philippine Islands today with Category 4 winds. Xangsane was a mere tropical storm yesterday, and was expected to hit the Philippines as a tropical storm or weak Category 1 typhoon at worst. Xangsane confounded the experts and put on a remarkable intensification spurt that brought it from tropical storm strength to a Category 4 typhoon in just 24 hours. The intensification was not expected, since the typhoon's circulation hugged the coast for much of this period.
Figure 1. Typhoon Xangsane at landfall in the Philippines. Image credit: Navy Research Lab.
The Philippines are very vulnerable to high death tolls from major typhoons, due to the high terrain that spawns deadly mudslides and floods. Xangsane is forecast to pass over the capital, Manila--the most heavily populated area of the country. These factors, plus the unpreparedness of the population due to the poor forecasts of Xangsane's intensification, make Xangsane a very dangerous storm for the Philippines. The last significant typhoon to affect Manila was 1995's Supertyphoon Angela, which killed 740, left 650,000 homeless, and caused severe damage to the agricultural areas surrounding the capital. Angela was one of 14 tropical storms or typhoons to affect the typhoon-prone Philippines that year.
Wind reports from Legospi and Catanduanes showed sustained winds of 63 mph and 45 mph, respectively so far today, with higher gusts. The winds have not yet picked up at the capital of Manila, where Xangsane is expected to pass Friday as a Category 2 typhoon. Interaction with land should weaken Xangsane on its passage over the Philippine Islands, but the typhoon should intensify once more this weekend into a major typhoon before hitting Vietnam.
New threat approaching Lesser Antilles Islands
A new area of concern has developed this morning near 17N 58W, about 500 miles east of the northernmost Lesser Antilles Islands, in association with a tropical wave moving west-northwest at 15 mph. The wave has developed a sharp increase in its heavy thunderstorm activity, and there are signs of a surface circulation in visible satellite imagery. Winds at a buoy at 16N, 58W, just to the south of the disturbance, have gone from northeast to north-northwest in the past few hours, signifying that this disturbance might have a closed circulation. Unfortunately, this morning's QuikSCAT pass missed the disturbance, and we'll have to wait until about 8pm EDT for a new pass. The disturbance will bring showers and gusty winds to the northern Lesser Antilles Islands Friday morning. The disturbance is under about 10 knots of wind shear, and the shear is expected to remain at 10 knots or below the next few days. This may allow some development, and we will need to keep a close eye on this wave. I imagine it will end up recurving between Bermuda and the U.S. East Coast, but it is too early to be confident of this.
We also need to watch the cloud-covered areas of the ocean surrounding the U.S. where cold fronts stall out over the next week. One such area to watch is off the North Carolina Outer Banks today, where a tropical low could develop and scoot quickly northeastward out to sea. The Western Caribbean near the Yucatan Peninsula could see some development early next week, when a strong cold front is expected to push off the East Coast of the U.S. and stall out over this region.
Disturbance 96L near tropical depression strength
The tropical wave (96L) we've been watching, at 26N 52W, about 850 miles east-northeast of the northern Lesser Antilles Islands, is near tropical depression strength. Wind shear has dropped from 20 knots yesterday to 15 knots today, which has allowed more heavy thunderstorm activity to build to the east of the center of circulation. The QuikSCAT pass from 5am EDT this morning showed winds of 25-30 knots (30-35 mph) in some of the heavier squalls. The storm is in a moist environment, the ocean beneath is warm, and I do expect that the shear will remain low enough to allow 96L to develop into a tropical depression in the next day or two, as forecast by the Canadian and GFDL models. All of the models predict that 96L will turn north and recurve out to sea, and will not be a threat to any land areas.
Figure 1. Preliminary models tracks for Invest 96L.
I'll have an update Thursday morning, or later today if the new wave approaching the Lesser Antilles islands looks significant.
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