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 , 1:51 PM GMT on July 26, 2006
The disturbance in the Gulf of Mexico has moved far enough on shore that it no longer has a chance to become a tropical depression. This system will bring heavy (and welcome!) rains to portions of Texas and Louisiana over the next two days.
Tropical Depression Daniel has decayed into a swirl of low clouds, and is expected to dissipate before reaching the Hawaiian Islands. All the Hurricane Hunter flights scheduled to investigate the storm have been canceled.
A tropical wave a few hundred miles east of the northernmost Lesser Antilles Islands is moving west to west-northwest at 15-20 mph. The amount of thunderstorm activity associated with this wave has increased over the past day, as the dry Saharan air surrounding the wave has gradually diluted. However, the wave is now under 30 knots of vertical wind shear. This wind shear is being created by the counter-clockwise flow of air around an upper-level low pressure system to the north of Puerto Rico. This low is not expected to move much the next five days, and should continue to create hostile wind shear over the wave. The wave will spread showers and gusty winds to Puerto Rico on Thursday, and the Bahama Islands on Friday and Saturday. By Saturday, as the wave approaches Florida, it will not be as close to the upper-level low, and the shear may lessen, potentially allowing some development. The wave is expected to turn north towards the Carolinas and not enter the Gulf of Mexico.
Figure 1. Water vapor image from 8:15 am EDT today shows a tropical wave surrounded by dry Saharan air approaching the Lesser Antilles Islands. The brown colors show the driest air, and whites and blues show where the most moisture is. You can see a large swirl of moisture north of Puerto Rico that marks the counter-clockwise rotating upper-level low pressure system that is bringing hostile wind shear over the tropical wave.
Long range forecast
The past four runs of the GFS model have consistently shown a powerful Cape Verdes-type hurricane forming off the coast of Africa August 3, tracking westward, and hitting the northernmost Lesser Antilles Islands on August 7. While I will be amazed if this forecast verifies--since our computer models are not very talented at forecasting tropical storm formation one day in advance, let alone a week or ten days in advance--it does serve as a reminder that we are entering August next week, and we should not be surprised if these most dangerous of hurricanes start forming from tropical waves coming off the coast of Africa.
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