Global Ensemble Ocean Wave Forecast System (Text)

The Global Ensemble Ocean Wave Forecast System (GEOWaFS) consists of the NOAA WAVEWATCH III^® (NWW3) wave model, an ensemble of 11 different Global Forecast System (GFS) wind fields and an initial wave field. The initial wave field adopts the same one used in the operationally deterministic NWW3. Eleven individual wave fields are generated using the NWW3 subject to the forcing of the 11 different wind fields respectively.

Out of these 11 wind members, one member is the operationally deterministic and the other 10 members are generated through introducing small, different perturbations to the initial atmospheric field using the breeding method. (Toth and Kalnay, 1993, 1997) This ensemble of the wind fields is operationally generated for up to 126 prediction hours at the 00, 06, 12 and 18Z run cycles. In the GEOWaFS, we use each of the 11 wind fields as the wind forcing to individually run the NWW3 to generate one member of wave prediction. Thus, a total of 11 wave predictions are generated and they constitute an ensemble for further statistical analysis.

Ensemble mean, spread and probability with various thresholds are then calculated from the ensemble of these wave and sea surface wind predictions. Wind speed, Significant Wave Height, and Peak Wave Period are viewable by selecting from the following table.

Important Note: GEOWaFS uses version 2.22 of WAVEWATCH III^®, not the multigrid version.

The viewer controls allow you to select from the last 5 days at the run times of 00Z, 06Z, 12Z, and 18Z. Spaghetti and Probability maps include a control to select a threshold value for the selected parameter.

References

Toth, Z. and E. Kalnay (1993): "Ensemble Forecasting at NMC: The Generation of Perturbations", Bulletin of the AMS, vol. 74, no. 12, pp. 2317-2330.

Toth, Z. and E. Kalnay (1997): "Ensemble Forecasting at NMC and the Breeding Method", Monthly Weather Review, pp. 3297-3319.