Evaluation of forecasts for hurricane Sandy

TitleEvaluation of forecasts for hurricane Sandy
Publication TypeTechnical memorandum
Date Published04/2013
Secondary TitleECMWF Technical Memoranda
AuthorsMagnusson, L, Thorpe, AJ, Bonavita, M, Lang, STK, McNally, A, Wedi, N

On 30th October 2012 hurricane Sandy made landfall on the U.S east coast with a devastating impact. In this report we evaluate the forecast performance from the ECMWF HRES and ENS forecasts together with ensemble forecasts from other NWP centres, available from the TIGGE archive. The results show that the ECMWF forecasts predicted the landfall 7-8 days in advance. We investigate the impact of the warm SST anomaly outside the U.S east coast by running sensitivity experiments with climatological SST instead of persisting the SST anomaly from the analysis. We find that the SST anomaly does not affect Sandy's track in the forecast. However, the forecasts initialised with the warm SST anomaly feature a more intense system. Furthermore we investigate the role of spatial resolution by comparing 4 different model runs, spanning from T3999 (5 km) to T159 (150 km) resolution. While all runs predict Sandy's landfall, at very high resolution the tropical cyclone structure and the the oceanic wave forecast is greatly improved. Finally we investigate the impact of omitting data from polar orbiting satellites on the ensemble forecasts, and find that the data has an impact on the ensemble forecasts, although even without the data some ensemble members correctly predict Sandy's landfall.

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