Thursday, May 01, 2008

More on the Virginia tornadoes

Last night, the Weatherbrains crew, consisting of meteorologists James Spann, Brian Peters, J.B. Elliott, and Kevin Selle, interviewed Meteorologist Brian Jackson of the Wakefield , Virginia National Weather Service Office. Mr. Jackson provided some insight into the tornado event that occurred in southeast Virginia on Monday. He said that so far seven tornadoes have been confirmed. Two were rated EF0, four were rated EF1, and one was rated EF3.

The first tornado touchdown was in the Colonial Heights area. Unfortunately there was no advanced warning for that tornado. According to Mr. Jackson, NEXRAD was showing no strong rotational signature. He said that this was spawned by a LWEP or line echo wave pattern and that the rotation formed very low. Interestingly the first report of this tornado came from a fellow NWS employee who was at the Best Buy store when the tornado occurred.

The worst (EF3) damage occurred around the north side of downtown Suffolk and near the Highpoint neighborhood and golf course. Warnings with adequate lead time were in place for this tornado and all other tornadoes after the first one. The Suffolk tornado was spawned by a supercell.

An EF1 tornado moved through the Norfolk Naval Base. Mr. Jackson referred to video that showed that tornado passing in front of the big battleship there.

Interestingly, the first tornado that struck the Colonial Heights area hit in the exact same spot as an F4 tornado in August of 1993. The 1993 tornado was the last major tornado in the area. Mr. Jackson said that their office has received numerous inquiries as to whether that spot was a “magnet” for tornadoes. He said that the fact it struck the exact same area was just random chance.

The Storm Prediction Center had placed southeastern Virginia under a slight risk for the five days prior to the event. Mr. Jackson said that the meteorological conditions did not seem to be coming together because Sunday was a rainy, overcast day with temperatures around 60. He said that the sun never really broke through much on Monday either. This makes me curious to learn whether this is yet another example of tornadoes forming in an area of strong shear but limited instability. It seems like many of the tornadoes this year have formed in that type of environment.

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