On the Utility of Global Ensemble Forecast Systems for Tropical Cyclogenesis Forecasts

Probabilistic Tropical Cyclogenesis forecasts have been analysed from the NCEP GEFS reforecast version 2 and operational ensemble forecasts. The utility and skill of producing ensemble based TC genesis forecasts with these systems will be presented along with example graphics developed to present ensemble forecast information quickly and efficiently. Analysis of the forecasts over the past 10 years highlights regions of low skill in the reforecast dataset, these regional biases are still evident in the operational forecasts. Through the analysis of reforecasts these regional biases can be identified and either be corrected or at least presented to the forecaster as regions of low confidence.

Case study analysis of high probability false alarms for Tropical Cyclogenesis from disturbances over the eastern Atlantic will be used to identify key characteristics in these boderline developing/nondevelopnig cases. These cases allow for understanding the predictability issues surrounding these forecasts, the subtle differences between developing and non-developing African Easterly Waves and the inherent biases within the respective modelling system.