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TD 2 forms in the Atlantic; hundreds feared dead from Typhoon Morakot; Felicia hits

By: Dr. Jeff Masters, 1:55 PM GMT on August 11, 2009

Tropical Depression Two has formed out of the strong tropical wave off the coast of Africa we've been watching, and has a good chance of becoming the Atlantic hurricane season's first named storm. Satellite loops of the storm show that heavy thunderstorm activity is increasing near the storm's center, and low-level spiral bands are getting better established. However, dry air to TD 2's north is interfering with this process, and the storm is being slow to organize. This morning's QuikSCAT pass missed TD 2.

Figure 1. Current satellite image of TD 2.

Wind shear over the storm is low, 5 knots, and is expected to remain low to moderate, 5 - 15 knots, through Thursday. Sea Surface temperatures are a marginal 26 - 27°C, and there is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly. However, does appear likely that TD 2 has enough going for it that it will be able to become Tropical Storm Ana later today or on Wednesday. Most of the computer models show some weak development, but none of them predict TD 2 will become a hurricane. It is unusual for storms forming this far north to make it all the way across the Atlantic to hit the Lesser Antilles Islands, and the current NHC forecast track aiming TD 2 north of the islands appears to be a good one.

Elsewhere in the Atlantic
Two other tropical waves, one passing through the Lesser Antilles Islands, and one about 600 miles east of the islands, are mentioned in NHC's Graphical Tropical Weather Outlook. Both of these waves have very limited heavy thunderstorm activity that is not increasing, and are not a threat to develop over the next two days. None of the computer models develop either of these waves.

A large, disorganized tropical wave is just leaving the coast of Africa, south of the Cape Verdes Islands. The GFS and ECMWF models continue to predict the possible development of this wave late this week.

Figure 2. Track and total rain amount from Typhoon Morakot. Image credit: NASA/GSFC.

Death toll from Typhoon Morakot in the hundreds
The death toll from Typhoon Morakot continues climb, as a landslide triggered by the storm's heavy rains hit the small town of Shiao Lin in southern Taiwan. Shiao Lin has a population of 1,300, and 400 - 600 people are missing in the wake of the landslide. Morakot killed an additional 41 elsewhere on Taiwan, with 60 missing. Earlier, the storm killed 22 in the Philippines, and went on to kill 6 in mainland China, which it hit as a tropical storm with 50 mph winds and heavy rain. Morakot's heavy rains caused an estimated $1.3 billion in damage to China.

Morakot moved very slowly as it passed over Taiwan, dumping near world-record amounts of rain. Alishan in the mountains of southern Taiwan recorded 91.98" of rain over a two-day period, one of the heaviest two-day rains in world history. The world 2-day rainfall record is 98.42", set at Reunion Island on March 15 - 17, 1952. Alishan received an astonishing 9.04 feet of rain over a 3-day period. The highest 1-day rainfall total ever recorded on Taiwan occurred Saturday at Weiliao Mountain in Pingtung County, which recorded 1.403 meters (4.6 feet or 55 inches) or rain. Nine the ten highest one-day rainfall amounts in Taiwanese history were reached on Saturday, according to the Central Weather Bureau.

Felicia continues to weaken, but is a flash flooding threat to Hawaii
Tropical Storm Felicia continues to steadily weaken, thanks to high wind shear of 30 knots. Recent satellite loops show that almost no heavy thunderstorm activity remains, and what little there is has been pushed to the northeast side of the center, exposing the surface center as a swirl of low clouds.

Figure 3. Tropical storm Felicia appeared as a swirl of low clouds with one spot of heavy thunderstorm activity to the northeast as it approached Hawaii yesterday evening.

High wind shear will continue to weaken Felicia today, and the storm is unlikely to cause major flooding problems as it moves over the islands today. The greatest danger of flooding will be over the northern islands, where Felicia's main moisture is concentrated.

Link to follow:
Wundermap for Hawaii

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I'll have an update Wednesday morning.


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