An Air Force Hurricane Hunter aircraft investigated the low pressure system centered about 150 miles southeast of the North Carolina/South Carolina border this afternoon, but did not find winds strong enough to support calling it a tropical depression. Peak winds were only 25 mph at the surface, and winds of 30 mph are required before NHC will classify a system as a tropical depression. The storm does have a well-defined closed circulation, but satellite imagery and long range radar out of Wilmington, NC
haven't shown much change in the system's organization today. With warm 84F (29C) waters underneath and wind shear of only 10 knots, I wouldn't be surprised to see this storm become a tropical depression or even a weak tropical storm by Thursday afternoon. However, the system has to act fast, since it will have a very hostile environment by Thursday night. A trough swinging off the East Coast today is expected to drag a filament of very strong jet stream winds southwards to Florida by Thursday night. These jet stream winds are forecast by both the GFS and NAM models to bring 100-150 knots of wind shear over the disturbance, which will easily tear it apart. Considering that wind shear over 20 knots is unfavorable for tropical storms, the 5pm NHC tropical weather outlook, "upper-level winds become increasingly unfavorable for development on Thursday", is a little understated!
High pressure building in behind the trough of low pressure should force the system towards the west or southwest through Thursday night. South Carolina could see some heavy rains and gusty winds Thursday night into Friday from the storm, but a storm strong enough to cause significant damage would be a major surprise.Figure 1.
Current long range radar out of Wilmington, NC.Figure 2.
Preliminary models tracks for the East Coast disturbance.Elsewhere in the tropics
There are no other threat areas to discuss. If you missed it, my discussion of the outlook for the remainder of August was posted in my previous blog.