Severe wind hazard using dynamically downscaled climate simulations

Tropical cyclones, thunderstorms and sub-tropical storms can generate extreme winds that can cause significant economic loss. Severe wind is one of the major natural hazards in Australia. In this study, regional return period gust wind hazard (10 meter height over open terrain) is determined using a new methodology developed by Geoscience Australia. The methodology involves a combination of three models: A Statistical Model (ie. data-based model) to quantify wind hazard using extreme value distributions. A methodology to extract gridded hourly maximum mean (time-step) wind speed and direction fields from a high-resolution regional climate model (RCM). Area-averaged measurements from the RCM are 'corrected' for point measurement exposure by applying a regional factor to the RCM values. And a Monte Carlo method to calculate gust wind from RCM mean wind, the former is the value of interest in wind hazard. To assess accuracy, model results were compared against three wind recording stations in Tasmania. These sites were selected because their weather stations and anemometer measurements are located at airports, avoiding the problem of houses or trees affecting the instruments, and also due to these sites having wind gust records. The model works only with synoptic gust wind speeds. A methodology to calculate severe wind gusts associated with thunderstorm down-burst winds is under development.