26th Conference on Hurricanes and Tropical Meteorology


Doppler-observed and model-simulated low-level wind surges in Hurricane Danny's (1997) eye wall

Keith G. Blackwell, University of South Alabama, Mobile, AL; and S. K. Kimball and A. Montoya

Hurricane Danny made landfall along the Alabama Coast in July 1997. The slow-moving storm drifted in Mobile Bay and remained within 50 km of the National Weather Service’s WSR-88D Doppler radar in Mobile for nearly 12 hours.

Although several aspects of Danny’s structural evolution have already been documented in earlier research (e.g., Blackwell 2000 and others), recent research suggests the existence of low-level wind surges within the intense convection in Danny’s western eye wall over Mobile Bay. Peak velocities approach 40-45 m/s. These wind surges are fairly persistent and display a periodic behavior, as several are recorded in the low-level Doppler velocity fields over a multi-hour period. It is hypothesized that this wind surge activity is associated with periodic eye wall meso-vortex development or intensification adjacent to heavy eye wall convection.

Using the PSU/NCAR mesoscale model, MM5, a simulation of hurricane Danny is carried out to investigate the relationship between eye wall meso-vortex development and low-level wind surges after the storm enters Mobile Bay, but prior to landfall. The model is initialized with GFDL initial fields and NAVY (OTIS) SST fields. The original GFDL bogus vortex, which was much larger than the real Danny, is removed and replaced with a smaller bogus vortex of similar intensity to Danny. Two domains are used with horizontal resolutions 9km and 3km respectively. The use of a 3 km horizontal resolution allows explicit modeling of convection, a process crucial to the accurate simulation of hurricane meso-vortex development.

extended abstract  Extended Abstract (108K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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