Surface observations of landfalling hurricane rainbands: case studies of Hurricane Bonnie (1998) and Hurricane Dennis (1999)

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Texas Tech University

This study examines the rainband-scale fluctuations of the meteorological parameters for Hurricane Bonnie (1998) and Dennis (1999). Since reliable surface observations near the locations of landfalling hurricanes are quite rare due to power and/or instrumentation failure. Wind Engineering Mobile Instrumented Tower Experiment (WEMITE) data are exploited to provide a unique look into the structure of the captured storms. The WEMITE data consists of high-resolution meteorological data—including wind speed and direction, temperature, relative humidity, and pressure— gathered from within the planetary boundary layer of landfalling hurricanes along the United States coastline.

WEMITE data, along with supplemental data gathered by the National Weather Service, buoys, Coastal Marine Automated Network (CMAN) stations, dropsondes and hurricane hunter observations, are assembled and analyzed through the use of Geographic Information Systems (GIS). Furthermore, nearby Next Generation Weather Surveillance Radar (NEXRAD WSR-88D) data are used to identify and examine rainbands found within the hurricanes of interest. The observed meteorological profiles are compiled and the results are compared to previous rainband studies.

The observed meteorological data suggest equivalent potential temperature minima, decreasing hurricane-relative inflow, and large-scale convergence to be commonly associated with intensifying or mature landfalling hurricane rainbands. Additionally, the results suggest larger rainbands (l00's of km long) promote updrafts and reflectivity redevelopment to the inside of their axis. The shorter bands (100 km or less in length), conversely, tend to form from one or a number of cells that are elongated into a band by strong hurricane winds with regeneration upband.

Hurricane Bonnie, 1998, Hurricanes -- Atlantic Coast Region, Rainfall frequencies -- Mathematical models, Atmospheric turbulence, Hurricane Dennis, 1999