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 , 3:40 PM GMT on August 31, 2013
A tropical wave that emerged from the coast of Africa on Friday (Invest 96L) is headed west-northwest towards the Cape Verde Islands. This wave is struggling against high wind shear of 20 - 25 knots. The shear is expected to drop to the moderate level on Sunday, then increase again to the high level on Monday through Thursday. In their 8 am EDT Saturday Tropical Weather Outlook, NHC put the 5-day odds of development at 40%, and the 2-day odds at 40%. Our reliable models for tropical cyclone genesis show little or no development of 96L. This disturbance is unlikely to affect any land areas except the Cape Verde Islands.
Figure 1. MODIS satellite image of Invest 96L off the coast of Africa, taken at 8:30 am EDT on August 31, 2013. Image credit: NASA.
Disturbance 96L moved very slowly across the Sahel region of Africa during the week, dumping torrential rains on Wednesday that triggered flash floods that killed at least 55 people in Mali's capital city, Bamako. Serious flooding also affected neighboring Burkina Faso, Gambia, Guinea, Niger and Senegal. Buildings have collapsed, roads have been rendered impassable, and valuable farmland is submerged beneath flood water, affecting over 200,000 people. More than 100 homes were swept away as the Niger River burst its banks, bringing down bridges and submerging entire streets.
Figure 2. People hold a rope to help rescuers climbing down a roof of a house in a flooded area of Bamako, Mail, on August 28, 2013. At least 55 people have been killed in flash floods caused by torrential rain. Image credit: HABIBOU KOUYATE/AFP/Getty Images)
Figure 3. MODIS satellite image of tropical wave 96L over Mali on August 28, 2013. The storm dumped torrential rains on Mali's capital city, Bamako, which killed at least 55 people. Image credit: NASA.
Disturbance approaching Lesser Antilles no immediate threat to develop
A tropical wave located about 400 miles east of the Lesser Antilles Islands is moving westward at 15 mph, and has changed little over the past three days. The wave has a modest amount of spin, but only a limited amount of heavy thunderstorm activity. In their 8 am EDT Saturday Tropical Weather Outlook, NHC put the 5-day odds of formation of this disturbance at 10%, and the 2-day odds at 0%. Wind shear is a high 20 - 30 knots over the system, and is expected to stay high through Monday. An area of dry air and dust from the Saharan Air Layer (SAL) surrounds the disturbance and is interfering with development. Wind shear may fall to the moderate level in 4 - 5 days when the wave reaches the Central Caribbean, increasing the odds of development then. Of our three reliable models for predicting genesis, the UKMET, GFS, and European models, only the UKMET model develops the disturbance, predicting it will become a tropical depression south of Haiti on Thursday. The wave will spread heavy rains and gusty winds to the Lesser Antilles Islands on Sunday and Monday.
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