The severe thunderstorm forecast and warning process in Australia

This overview paper will present the severe thunderstorm forecasting and warning process of the Australian Bureau of Meteorology. Severe thunderstorm forecasts and warnings are issued on a state by state basis using the Thunderstorm Interactive Forecast Preparation System (TIFS).

Severe thunderstorms are forecast 1-2 days in advance, primarily based on a variety of NWP models and the National Severe Thunderstorm Forecast Guidance System (NTFGS).

Severe thunderstorm warnings follow a two-tiered system. A "state-based warning" is issued for more rural areas of a state which is usually outside the radar coverage area. This type of warning is relatively broad in space and time and relies mostly on an assessment of the near-storm environment rather than a structural interrogation of existing storms.

In the metropolitan areas of some states quite specific cell-based severe thunderstorm warnings are issued. Now a larger component of the evidence supporting the warning decision stems from a detailed examination of the base reflectivity and base velocity structure of the storm. Radar-based algorithms such as the Thunderstorm Identification, Tracking Analysis and Nowcasting (TITAN) algorithm and the Warning Decision Support System (WDSS) are used as alerting mechanisms and safety nets. The radar-based and rain gauge-corrected rainfall algorithm RAINFIELDS is used as additional guidance for flash-flood warning decisions.