A Satellite Stereoscopic Technique to Estimate Tropical Cyclone Intensity

Abstract

Observations of the mean cloud top temperature and height of the eye wall of two tropical cyclones, using GOES infrared and stereoscopic measurements, presented an opportunity to estimate the storm's eye wall tropopause temperature and height. If it is assumed that for a mature tropical cyclone there is little dilution by outside air at the highest eye wall clouds so that the mean-equivalent potential temperature is constant with height from the surface to the cloud top (tropopause), then the mean equivalent potential temperature can be determined knowing the eye wall cloud top temperature and height. With knowledge of the storm's environmental equivalent potential temperature, using either climatological data or rawinsonde measurements together with the satellite derived eye wall equivalent potential temperature, estimation of either the storm's central pressure from the hydrostatic relationship or maximum winds from a cyclostrophic thermal wind relationship becomes possible. The technique was tested first on Hurricanes Frederic (between 1645 to 2115 GMT 12 September 1979) and Allen (at 2245 GMT on 8 August 1980). Hurricane Frederic's maximum surface wind and central pressure were estimated to be ?63 m s?1 and 945 mb, which compares well with reconnaissance aircraft measurements (58 m s?1/948 mb) near the time of the GOES observations. Allen's satellite derived maximum wind and central pressure were 78 m s?1 and 915 mb, which again compares favorably with aircraft measurements (73 m s?1/915 mb).