Poster Session P4.6 Documentation of the overland reintensification of Tropical Storm Erin over Oklahoma, August 18, 2007

Tuesday, 28 October 2008
Madison Ballroom (Hilton DeSoto)
John P. Monteverdi, San Francisco State Univ., San Francisco, CA; and R. Edwards

Handout (821.5 kB)

This manuscript documents the remarkable redevelopment of a tropical system over land. During the evening hours of 18 August 2007 to the early morning hours of the 19th, Tropical Depression Erin dramatically reintensified over Oklahoma. Maximum sustained winds of nearly 90 km h-1 (with gusts to over 120 km h-1) were recorded by the Oklahoma mesonet. The storm was associated with a small cluster of severe thunderstorm events, including tornado and wind reports. Radar and satellite plots showed that the storm developed an eye about the time that sustained tropical storm force winds were being observed. Observed Norman soundings and hodographs, both for the period of time prior to and following the passage of the storm, closely resembled composite soundings for hurricane environments. Subsynoptic analyses show that (a) the surface low was collocated with weaker cyclones at each successive level in the troposphere; (b) the system was warm core at each analysis level (evident both in the virtual potential temperature and thickness fields); and, (c) there was no evidence of the transition to baroclinic processes that often characterizes tropical systems after landfall and in the midlatitudes. This stage of Erin was classified as a "low" instead of a tropical storm by the National Hurricane Center, chiefly because the reintensification did not take place over ocean. The authors believe that the widespread flooding observed over Oklahoma during the days prior to Erin's arrival, along with a fetch of tropical air from the Gulf, provided an environment which effectively resembled that of the tropical ocean, and as such, established a similar boundary layer environment. We believe that Erin did indeed become a tropical storm in its transit over Oklahoma.

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