Tropical Cyclone Ensemble Forecast Windfields to 120hrs lead

Tropical Storm Risk (TSR) works with the insurance industry around the world to help manage the real-time risks associated with live tropical storms. Within its range of real-time products for tropical cyclones worldwide TSR offers an ensemble set of 100 different forecast windfield/gustfield datasets out to 120hrs lead. This innovative ‘ensemble forecast windfield' product is an advanced version of the ‘TSR forecast windfields' product. The product recognises that tropical cyclone wind-impact and wind-loss forecasts must be defined in terms of probability. It includes modelling of the uncertainty in storm track and storm intensity, the effect of storm size on the rate of inland windfield decay, and the impact of the change in surface roughness at landfall on wind/gust speed. The product has a user-friendly display with the wind contours of each ensemble member colour-coded at a range of thresholds up to Cat 5 strength (one minute sustained wind) and up to 190mph at 10mph intervals (3-sec maximum gust). The product is available within 20mins of a public tropical cyclone forecast advisory being released and is issued in a choice of four GIS formats. Assessments against station post-event wind observations worldwide 2004-2009 confirm the high accuracy of the product's wind modelling. The key features, accuracy, timeliness, availability and business benefits of the ‘TSR ensemble forecast windfield' product will be presented and described with examples.