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Tropical Cyclone Wind Radii Estimation Utilizing an Empirical Inland Decay Model

John Kaplan John.Kaplan@noaa.gov Hurricane Research Division/AOML Miami, FL 33149

Mark DeMaria Mark.DeMaria@noaa.gov NOAA/NESDIS/ORA/RAMMB Fort Collins, Colorado 80523

Nick.Carrasco@noaa.gov CIMAS/Hurricane Research Division Miami, FL 33149

Jason Dunion Jason.Dunion@noaa.gov Hurricane Research Division/AOML Miami, FL 33149

A revised version of the Kaplan/DeMaria decay model that better handles tropical cyclones that traverse islands and peninsulas was tested in real time during the 2006 hurricane season. Implementation of the updated version of the model required significant modifications to the code that was employed to run the original version. Specifically, a wind field on a cylindrical grid with 5 km radial and 15 deg. azimuthal spacing was generated every hour along the NHC forecast track. The shape of the wind field was determined every hour by fitting the NHC official forecasted storm structure, intensity, and storm speed along the forecast track using a modified Rankine vortex. The wind field on the cylindrical grid was then decayed for time periods when the storm was over land using the updated version of the decay model. For time periods when the storm moved back over water, the trend in the official NHC intensity forecast was employed to adjust the decayed wind field. The resultant wind field was then sampled at desired time intervals to obtain estimates of the maximum wind and the radius of 34-, 50-, and 64-kt winds. Since the updated decay model was not available for real-time testing until the middle of the 2006 hurricane season, the model was verified for hurricanes that made landfall from 2004 -2006. The results of these evaluations will be presented at the conference.

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