Extended Abstract (60K)5C.6
Tropical cyclone ensemble forecast product development and verification at the Met Office
Julian T. Heming, Met Office, Exeter, United Kingdom; and S. Robinson, C. Woolcock, and K. Mylne
In early 2002 The European Centre for Medium Range Weather Forecasts (ECMWF) introduced targeted perturbations in the tropics which, when run in its Ensemble Prediction System (EPS), produce an ensemble of tropical cyclone forecast tracks. The Met Office has been receiving these tracks since mid-2002 and has developed a number of graphical products to display the data. These include plots showing the tracks of all 51 ensemble members colour co-ordinated by lead time, strike probability charts similar to those issued by the National Hurricane Center and plots showing the geographical distribution of ensemble members relative to their forecast intensity tendency.
Methods of verifying the performance of the EPS have also been developed. EPS results were verified for the period July 2002 to March 2003 and compared to the deterministic forecasts from both the Met Office global model and ECMWF model. Preliminary analysis has indicated that the ensemble mean track forecast was better than the Met Office forecast at lead times of 72 hours and beyond and was better than the ECMWF deterministic forecast at all lead times except 48 hours. Results using the Brier Skill Score showed that the EPS was more skilful than both Met Office (to a lesser degree) and ECMWF (to a greater degree) deterministic forecasts. Verification of strike probabilities showed that the EPS forecasts were generally more reliable than the deterministic model forecasts.
Session 5C, Tropical Cyclone Prediction and Predictability I: Track
Tuesday, 4 May 2004, 8:00 AM-9:30 AM, Napoleon II Room
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