HYCOM RTOFS – Forecasted Eastward Ocean Currents (u-component) – September 21, 2025 00:00 UTC (initialized September 18, 2025 00:00 UTC)

The operational National Centers for Environmental Prediction (NCEP) Real-Time Ocean Forecast System (RTOFS) is based on an eddy resolving 1/12° global HYCOM (HYbrid Coordinates Ocean Model) and is part of a larger national backbone capability of ocean modeling at the National Weather Service in a strong partnership with the US Navy. RTOFS’ data assimilation methodology is based on NCODA, a three-dimensional (3D) multi-variate data assimilation process (Cummings, 2005). The assimilated data includes in-situ profiles of water temperature and water salinity and remotely sensed SST, SSH, and sea-ice concentrations (Mehra et al., 2011). The model is coupled with version 4 of the Los Alamos Sea Ice Model. The operational ocean model configuration has 41 hybrid layers. The grid has an Arctic bipolar patch north of 47°N and a Mercator projection south of 47°N through 78.6°S. The bathymetry minimum depth is 5m. The potential temperature is referenced to 2,000m depth. The forecast system is forced with 3-hourly momentum, radiation, and precipitation fluxes from the operational GFS fields. RTOFS does not include tides. RTOFS runs once a day and provides a nowcast and predictions for up to eight days of ocean currents, salinity, temperature, and sea ice conditions at a temporal resolution of 6 hours.