Observed Near-Surface Wind Flow Characteristics of Gulf Coast Hurricanes: 2004-2008

The continued deployment of ruggedized surface observing platforms by university research programs in the path of landfalling tropical cyclones has yielded a wealth of information regarding the near-surface wind flow characteristics at landfall. Data records collected by Texas Tech University's (TTU) Wind Engineering Mobile Instrument Tower Experiment (WEMITE), TTU StickNet probes, and the Florida Coastal Monitoring Program (FCMP) from landfalling hurricanes along the Gulf Coast of the United States from 2004-2008 were leveraged to examine the influence of storm-relative position on the near-surface wind flow. Archived composite reflectivity information from coastal WSR-88D radars was also assimilated with the tower records to investigate the influence of precipitation structure. Wind records were partitioned into 10-minute segments from which gust factor, turbulence intensity, and longitudinal integral length scale were extracted. Observations were stratified into terrain exposure categories to mitigate influence from surface frictional effects and changing upstream terrain. Wind flow characteristics within exposure classes were influenced by storm-relative position and precipitation structure. Eyewall observations resulted in the lowest mean gust factor and largest integral length; while outer-vortex convective observations produced a large length scale and slightly larger gust factors than those found in stratiform conditions. Within smooth terrain exposure, gust factors did not exceed 2.00. Gust factors typically decreased with radial distance, while integral length scales increased. No relationship between the turbulence parameters and vertical wind speeds or composite reflectivity were found. Integral length scales responded more readily to changing precipitation patterns relative to turbulence intensities and gust factors. Fortunately for residents along the Gulf Coast, the peak 10-minute mean wind speed within the dataset did not exceed 38 m s-1. The need exists for continued deployment of mobile observing platforms to collect information from higher mean wind speed events.