SURFACE WIND COMPARISONS WITH RADAR WIND PROFILER OBSERVATIONS NEAR TROPICAL CYCLONES

A special set of radar wind profiler observations during the Tropical Cyclone Motion (TCM-90) held experiment is used to relate lower-tropospheric winds to surface sustained winds and gusts on the west coast of Okinawa. Owing to the passage of four typhoons at various separation distances, hourly comparisons are possible for lower-tropospheric wind speeds ranging from 0 to 40 m s(-1). Regressions with nonzero intercepts provide more accurate estimates than simple ratios between lower-tropospheric winds and surface sustained winds and gusts. Little difference is found in use of a layer-average wind between 600 and 1800 m compared to regressions for individual levels. Stratification of the data into daytime and nighttime regression equations markedly improves surface sustained wind and gust predictions for wind speeds below 30 m s(-1). It is recommended that these daytime and nighttime regression equations be used to estimate surface winds over coastal regions when lower-tropospheric wind observations are available or when a tropical island wind report is available and a lower-tropospheric wind speed estimate is required.