Forecast guidance refers to computer-generated output that utilizes environmental forcing equations and observations to assist in the preparation of a forecast. Numerical weather and oceanographic forecast models produce forecast guidance for various oceanographic and atmospheric conditions at both the global and regional scales.
NOAA’s National Centers for Environmental Prediction (NCEP) develops and maintains several weather, ocean, and climate numerical guidance systems. A full list of the operational models run by NCEP can be found on their Numerical Forecast/Analysis Systems webpage. Descriptions of and links to the forecast modeling systems that are useful for navigation can be found below.
Animated precipitation map produced from a run of the Global Forecast System (GFS).
Global Forecast Modeling Systems
GFSwave
The model runs as a coupled component to the NCEP Global Forecast System (GFS) and Global Ensemble Forecast System (GEFS). The NWS/NCEP operational global wave model (WAVEWATCH III) produces forecast guidance for wave height, direction, and period, as well as wind speed and direction, throughout the world’s oceans was replaced by this model. Users can choose between local, regional, and full-basin forecast zones to view the forecast guidance for several wave and wind conditions (e.g., significant wave height; primary swell wave height; peak wave period). The model is run four times each day, and each run produces hourly forecasts out to 120 hours and 3-hour forecasts out to 180 hours.
Global Real-Time Ocean Forecast System (GRTOFS)
The National Weather Service (NWS) Global Real-Time Ocean Forecast System (GRTOFS) provides forecast guidance for water levels, water temperature, salinity, and currents out to 144 hours (6 days) for most of the world’s oceans. The "Nowcast/Forecast Viewer" allows users to visualize the forecast guidance of each condition, and the model data can be downloaded as individual NetCDF files, OpenDAP urls, and regional GRIB2 files. The model has one forecast cycle per day at 0000 UTC, which uses 3-hourly meteorological forecast guidance from the NWS/NCEP Global Forecast System (GFS); each forecast cycle is preceded with a 48-hr long nowcast/data assimilation cycle. The system uses the Hybrid Coordinates Ocean Model (HYCOM), an eddy resolving, hybrid coordinate numerical ocean prediction model; it has a horizontal resolution of 1/12 degree and 32 hybrid vertical layers.
NOAA (NOS) Global Extratropical Surge and Tide Operational Forecast System (Global ESTOFS)
NOAA’s Global Extratropical Surge and Tide Operational Forecast System (Global ESTOFS) provides users with nowcasts (analyses of near present conditions) and forecast guidance of water level conditions for the entire globe. Global ESTOFS serves the marine navigation, weather forecasting, and disaster mitigation user communities. The modeling system is run four times per day, and water level forecast guidance is provided out to 180 hours (nowcast for previous 6 hours followed by 7.5 day forecast). Forecast output includes water levels caused by the combined effects of storm surge and tides, by astronomical tides alone, and by sub-tidal water levels (isolated storm surge). The hydrodynamic model employed by Global ESTOFS is the ADvanced CIRCulation (ADCIRC) finite element model. Global ESTOFS has a coastal horizontal resolution of at least 1.5 km and up to 80 m globally. Global ESTOFS is a collaborative effort led by the NOAA/National Ocean Service (NOS)/Office of Coast Survey along with the NOAA/National Weather Service (NWS)/National Centers for Environmental Prediction (NCEP) Central Operations (NCO), the University of Notre Dame, Argonne National Laboratory, the University of North Carolina, and The Water Institute of the Gulf.
Coastal Forecast Modeling Systems
NOAA (NOS) Operational Oceanographic Forecast Modeling Systems (OFS)
NOAA provides forecast guidance for water levels, water temperature, salinity, and currents to help mariners safely navigate their local waters. The guidance is generated by a national network of numerical oceanographic forecast modeling systems for the next 48 or 120 hours depending on the water body. These forecast modeling systems are usually run four times per day (e.g. 0, 6, 12, and 18 UTC). The systems are implemented in critical ports, harbors, estuaries, Great Lakes and coastal waters of the United States, and form a national backbone of real-time data, tidal predictions, data management and operational modeling.
Depiction of surface currents for part of the New York/New Jersey Harbor, based on the OFS available there (NYOFS).
Nearshore Wave Prediction System
The Nearshore Wave Prediction System (NWPS) provides on-demand, high-resolution nearshore wave model guidance to U.S. coastal WFOs, triggered in real time by forecast wind grids prepared and submitted by the individual offices. Through an interactive map, users can find forecasts for significant wave height, peak period, wave direction, and wind speed out to 6 days for several stations along the U.S. coastline.
Advanced Hydrologic Prediction Service (AHPS)
Advanced Hydrologic Prediction Service (AHPS) is a new and essential component of the NWS’s Climate, Water, and Weather Services. AHPS is a web-based suite of accurate and information-rich forecast products. They display the magnitude and uncertainty of occurrence for floods or droughts, from hours to days and months, in advance. Although AHPS focuses mainly on forecasts of water levels along rivers, it does provide time series plots of observed and predicted water levels at many coastal locations.
