AN ENSEMBLE GLOBAL OCEAN WAVE FORECAST SYSTEM



Abstract:

We describe briefly the development and evaluation of the NOAA/NCEP ensemble global ocean wave forecast system (EGOWaFS) . In this context, the EGOWaFS consists of the NWW3 wave model, an ensemble of 11 different Global Forecast System (GFS) wind fields and an initial wave field. The initial wave field uses the same one in the operational NWW3. Eleven different wave fields are generated using the NWW3 subject to the forcing of the 11 different wind fields respectively. Ensemble mean, spread and probability with various thresholds are then calculated from the ensemble of these wave and sea surface wind forecasts. Buoy data in the months of May through July 2004 are used for wind and wave comparison between the NWW3 and the ensemble. Bias, root mean square error (RMSE) and correlation of the ensemble mean of the winds and waves are very close to those of the NWW3 respectively; the differences are minute. Trends of the ensemble spreads are well correlated to their corresponding RMSE. A storm event of June 03, 2004 near Buoy 46006 indicates that the wind and wave forecasts of the EGOWaFS, realized by the ensemble of wind and wave forecasts of each member, are indeed more reliable and realistic than those of the deterministic NWW3. Currently, the EGOWaFS is still under extensive study. It has run in parallel mode since December 2004 and is targeting for operational in June 2006. Ensemble wind and wave forecasts are currently post at the below experimental website and ftp site:

http://www.emc.ncep.noaa.gov/projects/wd21hc/ensemb/web/html/
ftp://polar.ncep.noaa.gov/pub/waves/test_hsc/ensemb_fd/

H. S. Chen