Modelling tropical cyclone over-water wind and pressure fields

Abstract

A parametric wind field model and an interactive computer tool are used to develop time histories of 2D wind field (surface wind speed and direction) during the 64 historical tropical cyclones that threatened the east coast of Queensland, Australia, during the 33 years (1969–2002) after the advent of meteorological satellite data for the region. These wind fields are suitable to be applied to applications such as wave, storm surge and circulation modelling. The parametric wind field model includes a double vortex and a representation of the synoptic winds in which the tropical cyclone is embedded. The process used all easily accessible meteorological data, including wind speeds, directions and pressures to determine the best-fit wind fields. Detailed comparisons between model and measurements for three individual storms are shown. These highlight the difficulties associated with fitting the parametric model to the very sparse measurements. If the storm did not pass close to a measurement station, then estimates of parameter values for radius of the storm and spatial shape of the wind field make the calibration process difficult and subjective. Nevertheless, results from the whole ensemble show that the modelled wind fields are unbiased with very good error statistics. These calibrations provide information for the distributions of values for radius of maximum winds and Holland B, parameters for which data are nonexistent in the Coral Sea region. An example of the use of the calibrated wind fields for the forcing of storm surge and wave models shows a very accurate comparison between modelled and measured surge and waves.