The tropical cyclone eyewall mesovortex: a physical mechanism explaining extreme peak gust occurrence in TC olivia, 4 april 1996 on barrow island, australia

摘要

A possible world reocrd peak 3-sec wind gust measurement of 220 kt (253 mph; 408 kph) was reorded on Barrow island, australia during the passage of Tropical Cyclone Olivia on April 10, 1996. This measurement was one of five extreme 3-sec gusts during a series of 5-min time periods. Gusts of 199, 220 and 202 kt were measured followed by a series of four lower values (minimum of 114 kt) which were then followed by two more extreme gusts of 187 and 161 kt in the 5-min time intervals. The elaspsed time between gust maxima was 30 min, representing a scale of 8 nm (15 km) compared to the eye diameter of 40 nm (75 km). The 5-min average winds showed maxima and a minimum at the same time periods as the gusts. The pattern and scales suggests that a mesovortes was imbedded in the already strong eyewall mean winds (5-min mean maximum wind chemical bounds 95 kt; 1-min mean maximum winds chemical bounds 106 kt). The extreme gusts represented extreme gust factors of 2.27-2.75, nearly twice the average ugst factor throughout the storm of 1.33. This clearly suggests that some process outher than mechanical turbulence is important during this period.