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-tropos pheric 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 interce pts provide more accurate estimates than simple ratios between lower-t ropospheric winds and surface sustained winds and gusts. Little differ ence is found in use of a layer-average wind between 600 and 1800 m co mpared to regressions for individual levels. Stratification of the dat a into daytime and nighttime regression equations markedly improves su rface sustained wind and gust predictions for wind speeds below 30 m s (-1). It is recommended that these daytime and nighttime regression eq uations be used to estimate surface winds over coastal regions when lo wer-tropospheric wind observations are available or when a tropical is land wind report is available and a lower-tropospheric wind speed esti mate is required.