Investigation of Gust Factors in Tropical Cyclones.
FLEET WEATHER CENTRAL/JOINT TYPHOON WARNING CENTER FPO SAN FRANCISCO 96630
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The 1972 Tropical Cyclone Conference requested that FLEWEACENJTWC include peak gusts in the warnings when sustained surface wind speeds equal or exceed 50 kts. During 1972, a sustained windpeak gust graph derived by former JTWC personnel was used. Details on how this graph was derived were not available and there was a general feeling among JTWC forecasters that the gust factors derived from this graph were too high for open water conditions. Therefore, at the 1973 Tropical Cyclone Conference, FLEWEACENJTWC requested that all 7th Fleet ships equipped with anemometers include peak gusts as well as sustained winds in their weather reports during strong wind conditions. These ship observations and a comprehensive literature survey led to the derivation of a new sustained windpeak gust relationship which was introduced into operational use by the JTWC during the 1973 season. This study showed that for strong wind conditions, gust factors i.e., ratio of peak gusts to one-minute average sustained wind speeds over open water should fall in the range of 1.20 to 1.25. Author