88th Annual Meeting (20-24 January 2008)

Monday, 21 January 2008: 11:15 AM
Calibration of Probabilistic ECMWF and GFS Temperature and Precipitation Forecasts Using Reforecasts
219 (Ernest N. Morial Convention Center)
Tom Hamill, NOAA/ESRL, Boulder, CO; and R. Hagedorn and J. Whitaker
We review results of calibrating daily probabilistic precipitation and temperature forecasts based on ensemble reforecast data sets for a newer (2005) ECMWF and older (1998) NCEP GFS models. We show that large training data sets are not necessary for the calibration of short-term temperature forecasts, but longer-lead temperature forecasts and precipitation forecasts benefit from large sample size. We also show that the decade-old GFS, after calibration, has more skill than the raw ECMWF forecasts. However, after calibration, the ECMWF forecasts are much more skillful than GFS calibrated forecasts, and a multi-model combination of the two is more skillful than either individually. We discuss the implications for operational usage of reforecasts.

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