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The 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. Data records collected by Texas Tech University’s Wind Engineering Mobile Instrument Tower Experiment and StickNet probes and by the Florida Coastal Monitoring Program along the Gulf Coast of the United States from 2004 to 2008 were compiled to examine influences on near-surface gust factors. Archived composite reflectivity data from coastal WSR-88D instruments were also merged with the tower records to investigate the influence of precipitation structure. Wind records were partitioned into 10-min segments, and the ratio of the peak moving-average 3-s-gust wind speed to the segment mean was used to define a gust factor. Observations were objectively stratified into terrain exposure categories to determine if factors beyond those associated with surface frictional effects can be extracted from the observations. Wind flow characteristics within exposure classes were weakly influenced by storm-relative position and precipitation structure. Eyewall observations showed little difference in mean gust factors when compared with other regions. In convective precipitation, only peak gust factors were slightly larger than those found in stratiform conditions, with little differences in the mean. Gust factors decreased slightly with decreasing radial distance in rougher terrain exposures and did not respond to radar-observed changes in precipitation structure. In two limited comparisons, near-surface gusts did not exceed the magnitude of the wind maximum aloft detected through wind profiles that were derived from WSR-88D velocity–azimuth displays.

Using wind-speed records from mobile weather stations deployed in tropical cyclones making landfall along the United States coastline over the period 1998-2008, an analysis was made of the gust factors observed in near-neutral conditions by station site and wind direction. The dataset used contained a total of 56 individual station site/wind-direction combinations representative of a wide variety of terrain conditions, ranging from open water to urban exposures. Consideration of the peak gust measured along a given axis, together with the associated components measured simultaneously along the other two axes, showed that peak along-wind gusts are primarily associated with vertical velocities in air moving towards the surface, while peak downwards and upwards vertical gusts are associated with alongwind velocity components that are respectively larger and smaller than the mean along-wind velocity. This behaviour is directly related to the value of the primary component of the surface shear stress in the coordinate system used for the analysis, which involves the product of the along-wind and vertical velocity components and which must be negative in the surface layer. Grouping the mean gust-factor curves for each velocity component into bins based on the turbulence intensity showed that the individual curves in a given bin could not all be considered to be drawn from the same underlying parent distribution, an observation that was confirmed by statistical testing. A quantitative exploration of the effects of upstream terrain variations on the observed gust factors for a selected number of sites suggested that the gust factors and other flow parameters, such as the turbulence intensity, are heavily influenced by the upstream terrain at many of the station sites considered.