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 , 11:22 PM GMT on September 06, 2006
Florence continues to struggle with wind shear today, and is managing just a slow intensification. Compounding Florence's troubles is the presence of some dry air at mid levels, as revealed this afternoon in the appearance of arc clouds at the surface. Dr. Jason Dunion of NOAA's Hurricane Research Division has posted a blog this evening showing some examples of these arc clouds. What happens is that a ribbon of dry air at mid levels gets sucked into a thunderstorm inside of Florence, which then creates a strong downdraft that leaves its mark at the surface as an arc cloud that expands out in a semicircle.
Hurricane Hunters in the air
The Air Force Hurricane Hunters are in the air off the North Carolina coast investigating a new area of concern that developed along the old cold front off the Carolina coast. So far, they've found peak winds of 20 mph at flight level (500 feet), but they aren't done investigating the system yet. This storm, designated "Invest 92L" by NHC this afternoon, is expected to move rapidily northeast away from North Carolina and become an extratropical storm Thursday night. If the Hurricane Hunters find a tropical depression, I'll post an update tonight.
Figure 1. Preliminary model tracks for Invest 92L, a tropical disturbance off the North Carolina coast.
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