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ABSTRACT
A real-time hurricane wind forecast model is developed by 1) incorporating an asymmetric effect into the Holland hurricane wind model; 2) using the National oceanic and Atmospheric Administration (NoAA)/ National Hurricane Center's (NHC) hurricane forecast guidance for prognostic modeling; and 3) assimilating the National Data Buoy Center (NDBC) real-time buoy data into the model's initial wind field. The method is validated using all 2003 and 2004 Atlantic and Gulf of Mexico hurricanes. The results show that 6- and 12-h forecast winds using the asymmetric hurricane wind model are statistically more accurate than using a symmetric wind model. Detailed case studies were conducted for four historical hurricanes, namely, Floyd (1999), Gordon (2000), Lily (2002), and isabel (2003). Although the asymmetric model performed generally better than the symmetric model, the improvement in hurricane wind forecasts produced by the asymmetric model varied significantly for different storms. in some cases, optimizing the symmetric model using observations available at initial time and forecast mean radius of maximum wind can produce comparable wind accuracy measured in terms of rms error of wind speed. However, in order to describe the asymmetric structure of hurricane winds, an asymmetric model is needed.
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1. Introduction
Hurricane-induced storm surge and flooding remain a severe threat to coastal communities despite progress made over the past several decades on improved hur- ricane track and intensity forecasts. The accuracy of a storm surge forecast depends not only on the track and intensity, but also on the distribution of the forecast wind field. A variety of numerical and statistical models have been developed for forecasting (e.g., Holland 1980; Jelesnianski et al. 1992) and hindcasting hurricane wind fields (e.g., Powell and Houston 1998; Houston et al. 1999). The extensive resources needed in the use of full physics mesoscale models have kept them from be- ing adopted in routine operational forecasts of hurri- cane winds. instead, simple parameterized models are widely used in the simulations of hurricane wind fields and for providing hurricane forcing for storm surge forecasting. Early studies (Depperman 1947; Hughes 1952; Riehl 1954, chapter 11) used a modified Rankine vortex to approximate the structure of a generic tropi- cal cyclone (TC). The deficiency of the modified Ran- kine vortex model is that...