Joint Poster Session JP2.3 Factors contributing to sensitivity in the observed overland reintensification of TC Erin (2007) over Oklahoma

Tuesday, 2 June 2009
Grand Ballroom Center (DoubleTree Hotel & EMC - Downtown, Omaha)
Clark Evans, NCAR, Boulder, CO; and T. J. Galarneau Jr. and R. S. Schumacher

Handout (106.5 kB)

The dramatic overland reintensification of North Atlantic TC Erin (2007) on the morning of 19 August 2007 drew national attention for its tropical-like structure and intense rainfall and wind speeds across much of central Oklahoma. This reintensification was observed despite nearly three days passing from the time it made landfall along the central Texas coastline as a weak tropical storm. In fact, Erin's peak intensity was reached over Oklahoma (50 kt, 995 hPa) rather than over water (35 kt, 1003 hPa), a rare feat for a tropical cyclone. What contributed to this evolution, however, has remained somewhat of a mystery with hypotheses ranging from high values of soil moisture located over western Oklahoma to more traditional continental severe local storm processes proposed to understand this evolution.

In this study, we present results from a suite of high resolution WRF-ARW simulations, including simulations focusing only upon the overland reintensification of the cyclone as well as those focusing on the entire life cycle of the cyclone from genesis to decay. Despite the track of the cyclone over the Southern Plains being remarkably hard to successfully model, with forecast tracks for 19 August ranging from west Texas to central Oklahoma, nearly all simulations result in a period of overland reintensification on the morning of 19 August. The mechanisms behind this reintensification are explored with special attention given to understanding the sensitivity in this evolution, particularly to the track of the cyclone, structure of the cyclone's circulation atop the frictional boundary layer, and the role(s) of external influences such as midlatitude troughs and nocturnal jets.

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