Thursday, 15 August 2002: 4:30 PM
Tornado Distribution Associated with Hurricane Floyd 1999
Albert E. Pietrycha, Penn State Univ., University Park, PA; and C. D. Hannon
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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.
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