Monday, August 20, 2007

Tropical Storm Erin Postmortem

From Dr. Jeff Masters' blog this morning:
Tropical Storm Erin finally died this morning over Missouri. Erin dramatically re-intensified Saturday night over Oklahoma, forming a tropical storm like-vortex that brought up to 11 inches of rain to Oklahoma, and helped feed disastrous rains of up to a foot over southeastern Minnesota. At least 13 deaths are being blamed on the resulting flooding, six of them in Oklahoma. The radar presentation of Erin's remains (Figure 3) looks remarkable tropical storm-like, and such re-intensifying tropical cyclones over land, complete with calm eye and spiral bands, have been observed in Australia, where they have been dubbed "landphoons". Hurricane David of 1979 performed a similar feat, generating severe weather over Washington D.C. 27 hours after it had made landfall in Georgia. What seems to be happening in these cases is that the circulation at upper levels of the atmosphere can remain intact if there is not a lot of wind shear to tear it apart. This circulation can then reach down to the surface again during its passage far inland. I've saved a long animation of this "landphoon", and Dr. Kevin Kloesel of the University of Oklahoma provided me a plot showing that the winds in Fort Cobb, Oklahoma were sustained at tropical storm force for over 10 minutes Sunday morning, with a peak wind gust of 75 mph.
See my post yesterday for an image of the storm. I gathered that if one were trying to travel to Kingfisher that the roads would have been pretty treacherous, and from my peeps in the OKC metro area the gist of their email was that there was plenty of urban flooding.

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