The new ECMWF VAREPS (VAriable Resolution EPS)

Roberto Buizza

The key idea behind the new ECMWF VAREPS is to resolve small-scales in the forecast up to the forecast range when resolving them improves the forecast, but drop them when their impact is negligible.

VAREPS aims to increase the value of the current EPS in two ways: up to forecast d7, by providing more skillful predictions of small-scale, severe events, and after forecast d7, by extending the range of skillful products from 10 to 15 days. VAREPS will also provide the first 2-legs of ECMWF planned seamless ensemble system, which will be extended initially to one month, and then to a longer forecast time.

During this talk, average results of the new VAREPS system, and predictions for some case studies (e.g. the 2005 hurricanes Katrina and Stan) will be shown. Plans for future developments of the ECMWF ensemble systems will also be discussed.