Is Danny really a tropical storm?

August 27, 11:18 PMRaleigh Climate ExaminerDean Grubbs

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Is Danny really a tropical storm? Such a system would feature a defined circulation of strong thunderstorms and maximum sustained winds between 39-74 mph (Wikipedia). The Plymouth state weather center specifies that even a depression must have a defined circulation.

The National Hurricane Center also defines a Tropical Cyclone as being a "A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center."  They further specify that " a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects)."

I ask again: based on the above information is "Danny" really a Tropical Storm?

What I see in the water vapor signature below is a loosely organized cluster of thunderstorms which lacks a visible center of circulation.  The Tropical Upper Tropospheric Trough has a very organized center of circulation near New Orleans compared to "Danny".

Water Vapor Image from Univ of Wisconsin SSEC 10:00 PM EDT
27 Aug 2009

 

 The 1100 PM Danny Discussion was just released. In it the forecasters describe the storm as being disorganzed and possibly "becoming" an extratropical cyclone.  The strongest winds being "displaced" well northeast of the center is a non-tropical characteristic.  Furthermore the Forecast Advisory defines Danny's lowest pressure as being 1008 mb and shows no tropical storm force winds in the SW quadrant.  Further research reveals that there is a 1024 mb High located in the NE Atlantic which is apparently providing contrast to the storm's low pressure.

Therefore my analysis of the situation is that Danny is either an open tropical wave with baroclinic characteristics (the contrast between high and low pressure) or he is merely a cluster of strong thunderstorms NE of a dying center.

Whether the storm system attempts to reorganize in a tropical fashion or not will have a big effect on how the interaction between the TUTT  located to its west and a very strong cold front moving in our direction from the north.  Coastlines would welcome the demise of Danny.  Could energy and moisture from the system enhance NC and VA thunderstorm activity on Friday and Saturday?  Stay tuned!