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Atlantic tropical update; Category 4 Typhoon Krosa slams Taiwan

By: Dr. Jeff Masters, 2:56 PM GMT on October 06, 2007

A tropical wave (91L) near 14N 51W, 650 miles east of the Lesser Antilles Islands, has become better organized today. Satellite loops show that 91L has developed a surface circulation and some heavy thunderstorm activity on the southeast side of the center. The storm may be close to tropical depression status, but wind shear of 20-30 knots over the system should keep further development very slow. By Sunday evening, wind shear should drop below 15 knots, and 91L may be able to develop further. The storm is headed northwest, and is expected to recurve out to sea without affecting any land areas.

Figure 1. Microwave satellite image of 91L showing some heavy thunderstorm activity on the southeast side of the storm. There is some hint of low-level spiral banding beginning to develop on the the lower left of the image, on the storm's south and southwest side. Image credit: Navy NRL Monterey.

Puerto Rico disturbance
A tropical disturbance (93L) about 200 miles north of Puerto Rico is kicking up some disorganized heavy thunderstorm activity that is visible on long range Puerto Rico radar. This morning's QuikSCAT pass showed very little in the way of a wind shift or strong winds. This disturbance is under 10-20 knots of wind shear, and may show some development over the next few days as it moves slowly north or northwest. Most of the models expect 93L to recurve out to sea without affecting any land areas. However, steering currents are weak in the region, and recurvature is not a sure thing. The GFDL models predicts 93L could become a weak tropical storm 5 days from now, but none of the other models develop the storm. The Hurricane Hunters are on call to investigate this disturbance Monday, if needed.

Western Caribbean disturbed weather
Limited and disorganized thunderstorm activity is present over the Western Caribbean. This area has been labeled "Invest 94L" by NHC this afternoon. Most of the computer models continue to show the possibility of a tropical depression forming here in the next 2-7 days, and moving over the Yucatan Peninsula. Given the current lack of activity there now, nothing is likely to develop today, but the Hurricane Hunters are on call to fly Sunday, if needed. Upper level winds over the Western Caribbean and Gulf of Mexico are forecast to be favorable for tropical storm development over the coming week, if a disturbance with some spin at low levels can get going.

Super Typhoon Krosa smashes into Taiwan
Typhoon Krosa, a formidable Category 4 storm with 145 mph winds, is making landfall in the northern portion of Taiwan. Latest Taiwan radar shows the storm well. Krosa has already killed at least two people and brought rains of 16 inches to portions of Taiwan. Rainfall may exceed one meter (39 inches) in some mountainous regions of the island. Krosa is the Cambodian word for crane.

Figure 2. Radar image of Krosa as it hit northern Taiwan at 14:30 GMT Oct 6, 2007. Image credit: Central Weather Bureau of Taiwan.

I'll have an update Sunday morning.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.