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Posted at 11:25 AM ET, 08/26/2009

Meet Tropical Storm Danny

By Greg Postel

Impacts on U.S. uncertain; Worst may stay offshore

* Our Full Forecast | UnitedCast | Hurricane Tracking Center *


Infrared satellite view of Tropical Storm Danny this morning. As of 11 a.m., Danny was about 775 miles south-southeast of Cape Hatteras, N.C. Courtesy NOAA.

By Greg Postel, Hurricane Expert

The National Hurricane Center has named the poorly organized cloud mass east of the Bahamas Tropical Storm Danny. Though Danny's top winds have increased to 45 mph, the system will need to overcome significant obstacles if it is to intensify into a hurricane.

A minority of the recent model runs hint that the Outer Banks of North Carolina may feel some of Danny's effects within about three days. There is much uncertainty in this scenario, however, with higher rain chances, breezy conditions and big surf the primary threats.

Just as uncertain is whether any of Danny's rains or breezes will affect the D.C. area and Eastern Shore late Friday into this weekend.

Keep reading for more on Tropical Storm Danny...


Satellite image showing location and strength of Saharan Air Layer -- dry air that originates from the Sahara Desert in North Africa. Courtesy University of Wisconsin.

At this time, Danny's circulation is associated with an upper-level cyclone, and very likely has many attributes similar to that of a midlatitude system (e.g., a Nor'easter). This setup is typically hostile to tropical development. In particular, the dry, non-tropical air on its periphery (red shading in image to the right) and the strong wind shear (winds that change direction and/or speed with height and tend to rip storms apart or prevent them from getting stronger) near the edges of the circulation tell me that it has yet to acquire truly tropical characteristics.

The nearly comma-shaped asymmetry in the cloud pattern tells us that the ingredients for significant intensification are not yet in place. Most of the thunderstorm activity is displaced well to the east of the center of the low-level swirl, typical of a highly sheared circulation.

The latest track guidance suggests that the system will likely re-curve away from the United States as it moves north, thanks to a strong midlatitude low-pressure system that is on its way to the East Coast from central Canada. The midlatitude feature should arrive in time to deflect Danny away from shore (similar to what we saw with Hurricane Bill).

The approach of the midlatitude system should also limit Danny's chances for intensification. Even in the event the center makes a close approach to the coast, the worst weather should be displaced east of the center's track and remain offshore.

By Greg Postel  | August 26, 2009; 11:25 AM ET
Categories:  Tropical Weather  
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Comments

Kennedy funeral Saturday afternoon in Boston, about the time Danny arrives there. Are they sure they know what they are doing?

Posted by: RossPhx | August 26, 2009 7:49 PM | Report abuse

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