About Jeff Masters
Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 11:30 PM GMT on July 12, 2005
Satellite imagery shows that the deep convection at the center of Emily continues to become better organized, nice banding features have developed, and upper-level outflow is steadily improving. Emily is advancing over warmer and warmer waters, and the upper-level winds ahead of it look very favorable for intensification. NHC brings Emily up to a Category 3 in three days' time, and I cautiously agree.
Cautiously, because I note that Emily is now moving a little south of due west--it's latitude went from 11.4 to 11.0 North the past six hours. This may have been due to an internal re-organization where the center got sucked underneath where the deepest convection was. The computer forecast models predict that a west to west-northwest motion should begin shortly. However, if Emily's motion continues westward or slightly south of westward, the storm will enter the southeast Caribbean Sea--which historically has been very unfavorable for tropical storms. I've seen countless impressive-looking tropical storms cross through the Windward Islands between 11 and 13 North Latitude, only to weaken or die once they get into the southeastern Caribbean. The reasons for this weakening are not well understood, but one theory is that the presence of the South American land mass to the south cuts off an important source of low-level moisture to developing tropical storms, or entrains dry air into them.
If one looks at the past 20 years of data and finds all hurricanes and tropical storms that crossed into the southeast Caribbean between 11 and 13 North Latitude, here's what one finds:
Two tropical storms that weaken, but later regain their strength:
Six tropical storms that die:
Two tropical storms that intensify into hurricanes:
One hurricane that intensifies:
So, in the past 20 years, over 70% of the tropical storms and hurricanes that have crossed into the southeastern Caribbean have died or weakened. But this is the hurricane season of 2005. The normal rules do not apply. Or in the words of NHC hurricane forecaster Dr. James Franklin in today's 5pm discussion, "So far...the 2005 hurricane season seems to have little interest in climatology."
I predict Emily will follow it's namesake storm, Emily of 1987, and continue to intensify once it crosses the Windward Islands into the southeastern Caribbean.
Dr. Jeff Masters
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