The Distribution of Surface Winds In Pacific Typhoons

Low-level wind data from the WSR-88D in Guam were collected in Typhoon Dale (1996) and Typhoon Keith (1997) and analyzed for coherent structures. Consistent with the results of previous studies of Atlantic hurricanes, velocity anomalies associated with coherent structures were found in the typhoon boundary layer of both storms.

Coherent structures consistent with roll vortices were documented in 99 cases during a six-hour evaluation period for each storm. Storm relative roll location, roll vorticity, asymmetries in the updraft and downdraft portions of rolls as well as differences in the upward and downward momentum fluxes resultant from the roll circulations are addressed for the first time in this study. This research supports the findings of prior roll observations and theoretical work.

A wind speed record is obtained and evaluated from a land-based, high-resolution anemometer on Guam during Typhoon Paka (1997). A power spectrum is created from anemometer data to help better understand the kinetic energy distribution of the winds in a tropical cyclone. A technique is developed to create a time series of wind speed from the WSR-88D.

The results presented here can be used in further testing and development of theoretical and numerical models of secondary circulations within tropical cyclones. Moreover, the wind variations documented in this study have application for wave run-up and the structural-damage potential in tropical cyclones.