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National Weather Service Marine Forecasts

National Weather Service Plans for Marine Forecast Data
In Gridded and Vector Formats for
Display on Electronic Charts and Other Value-Added Applications

The National Weather Service (NWS) makes available to the public, the computer generated model guidance products used by marine forecasters popularly known as “GRIB Files”. These data are used for display on electronic chart navigation systems and other value-added software such as routing systems, provided by commercial vendors. However, this direct model guidance is not validated by marine forecasters and may be misleading. Mariners are urged to use these data in conjunction with forecaster generated forecasts.

High seas marine forecasts in graphic form are prepared by NWS forecasters for broadcast via radiofax and made available via the Internet. However, these charts are presently only made available in raster format which cannot be readily integrated with value-added software, limiting the value of these forecasts to mariners.

NWS has now deployed new workstation technology and software known as the Interactive Forecast Preparation System (IFPS) software to prepare modernized products. Forecasters using the IFPS software prepare these forecast products by modifying the grids of sensible weather elements that are derived from NWS numerical model forecasts and guidance products. Products are generated from the IFPS digital database in various formats such as text, tabular, graphical imagery, and as grids.

46 of 122 NWS Weather Forecast Offices (WFOs) are responsible for preparing forecasts for the U.S. Coastal waters and Great Lakes. Experimental gridded data and graphical imagery is now routinely produced at most WFOs. It is expected that continental U.S. WFOs with Marine responsibility will begin to operationally forecast gridded weather elements of interest to the maritime community such as: wind speed, direction, and gusts; weather; and wave height by December 2004. Gridded forecasts from the other non-continental U.S. WFOs are scheduled to become available in 2005. It is planned that the high seas forecasts generated from the Ocean Prediction Center (OPC) [formally the Marine Prediction Center], and the Tropical Prediction Center (TPC) will begin to be made available in gridded format by (date TBD). Gridded forecasts and analyses from TPC and OPC will be provided for sea level pressure, wind speed and direction, significant wave heights, peak swell direction and peak swell period.

The forecast grids generated from each WFO are collected centrally at a server and also combined into national scale and regional scale grids. Gridded forecasts from the TPC and OPC will also be made available from this central server. A database system, the National Digital Forecast Database (NDFD) is the dissemination system for these grids. These products are in a new gridded format, known as Gridded Binary 2 (GRIB2) a standard format for meteorological data. The gridded data used to create graphical imagery presented in Portable Network Graphics (PNG) format.

Links to NDFD Data:

  • Example of NDFD Graphical Imagery (experimental)
  • NDFD GRIB2 data via FTP (experimental)
  • NDFD Extensible Markup Language (XML) Service (experimental)
  • NDFD Graphical Imagery (experimental)
  • Link to NWS Forecast Offices (WFO's) and Centers*

    * NWS Forecast Offices provide direct links to their products and several make available larger scale and/or higher resolution NDFD graphics than is available on the NDFD graphics webpage.


    Experimental gridded data and imagery using past data is now available from the OPC.

    Example gridded data and imagery from OPC

    A suitable file format for vector data such as the location of weather fronts is under study.


    For further information contact:

    Tim Rulon
    301-713-1677 x128

    Marine and Coastal Services Branch W/OS21
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910

  • National Weather Service
    Office of Climate, Weather, and Water Services
    Marine and Coastal Weather Services Branch (W/OS21)
    Last modified: Nov 01, 2005
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