Tropical cyclone wind probability forecasting for the southern hemisphere
The development of a model to estimate 30 and 50 kt wind probabilities from Southern Hemisphere tropical cyclone forecasts i s described. The model is based on position forecast errors, which are used to determine the probability of a tropical cyclone occupying a particular geographical position, and on wind profile errors. Wind profile errors consist of errors in the forecast maximum wind and errors in the forecast radius of 30 kt and 50 kt winds. The profile errors are used to estimate the probability of 30 and 50 kt or greater winds occurring at a point, given that the tropical cyclone occupies a particular position. These position and wind probability elements are combined by using an assumption of independence which was supported by correlation coefficients in an earlier work. The model, which includes features of earlier strike and wind probability models, is tested on independent data. Test results show good agreement between forecast probability and the frequency of 30 and 50 kt or greater winds. Several operational products are also shown and explained.