21st Conf. on Severe Local Storms


Tornado Distribution Associated with Hurricane Floyd 1999

Albert E. Pietrycha, Penn State Univ., University Park, PA; and C. D. Hannon

On the evening of 15 September 1999, Hurricane Floyd made landfall at Bald Head Island, NC; 0630 UTC 16 September. Floyd was a large and intense Cape Verde hurricane that affected the central and northern Bahamas before making landfall on the North Carolina coast. At its peak intensity, Floyd reached the top end of category four (with winds >69 m s-1) on the Saffir/Simpson hurricane scale, and arrived onshore as a category two hurricane. Prior to and during the time of landfall the hurricane interacted with a coastal front situated along the coastal plain of the Carolinas and Virginia, and remained coupled with the front as the hurricane weakened rapidly, and accelerated northward along the East Coast into New England.

Eighteen tornadoes associated with Floyd were reported in the U.S. and all occurred in North Carolina on the day of landfall. 88.9% (16 of 18) of the tornadoes developed immediately along and/or within the warm side of the coastal front. The two strongest tornadoes produced F2 damage. Cross-sectional analysis normal to the front of potential temperature utilizing rawinsonde data, and surface observations revealed a 1 km deep surface layer of cold air existed westward from the coastal front to the mountains of North Carolina and Virginia. The lack of tornadoes west of the boundary was attributed to the inhibiting influence of the strong cold pool west of the coastal front. In this case, the possibility for tornado genesis appears to have been greatly diminished, given the elevated nature of the storms along and over the cold pool.

extended abstract  Extended Abstract (204K)

Session 15, Tropical Cyclone Tornadoes and Low-Latitude Severe Storms
Thursday, 15 August 2002, 4:30 PM-5:30 PM

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