Numerical data from the GDWPS in GRIB2 format

The Global Deterministic Wave Prediction System (GDWPS) produces wave forecasts using the third generation spectral wave model WaveWatch III®. The model is forced by the 10 meters winds from the Global Deterministic Prediction System. In addition, a sea ice forecast from the Global Ice-Ocean Prediction System (GIOPS) is used by the model to dampen or suppress wave growth in areas covered respectively with 25% to 75% and more than 75% ice.

The WW3 (Tolman and the WAVEWATCH III® Development Group 2014) is a third generation spectral wave prediction model that solves the evolution of the energy balance equation for the 2-D wave energy spectrum without any prior assumptions on the shape of the spectrum. The WW3 model has been implemented by a growing number of national operational forecasting centres over the last several years.

Global

Download

The data is available using the HTTP procotol and resides in a directory that is plainly accessible to a web browser. Visiting that directory with an interactive browser will yield a raw listing of links, each link being a downloadable GRIB2 file. In practice, we recommend writing your own script to automate the downloading of the desired data (using wget or equivalent). If you are unsure of how to proceed, you might like to take a look at our brief wget usage guide.

The data can be accessed at the following URLs:
http://dd.weather.gc.ca/model_wave/ocean/global/grib2/HH/
where:

• HH: model run start, in UTC [00 or 12]

File name nomenclature

The file names have the following nomenclature:
CMC_gdwps_domain_Variable_LevelType_level_latlondddxddd_YYYYMMDDHH_Phhh.grib2

where:

• CMC: constant string indicating that the data is from the Canadian Meteorological Centre
• gdwps: constant string indicating that the data is from the Global Deterministic Wave Prediction System
• domain: constant string indicating which domain that the data is from
• Variable: Variable type included in this file.
• LevelType: Level type.
• Level: Level value.
• latlon0.dx0.dd: constant string indicating that the projection used is lat/long at 0.dd x 0.dd degrees resolution
• YYYYMMDD: Year, month and day of the beginning of the forecast.
• HH: UTC run time [00, 12]
• Phhh: P is a constant character. hhh is the forecast hour [000, 001, 002, ..., 048, 051, ..., 120]
• grib2: constant string indicating the GRIB2 format is used

Example of file name:
CMC_gdwps_global_HTSGW_SFC_0_latlon0.25x0.25_2017092112_P096.grib2

This file originates from the Canadian Meteorological Center (CMC) and contains the data of the Global Deterministic Wave Prediction System. The data in the file start on September 21th 2017 at 12Z (2017092112). It contains the significant wave height (HTSGW) for the world at the surface (SFC_0) on a lat/long grid at 0.25 degree x 0.25 degree resolution for the forecast hour 096 (P096) in GRIB2 format (.grib2).

Levels

Levels that may be applicable to a given parameter are:

• surface
• fixed height above ground

Note: Swell parameters no longer refer to the total swell, they now refer to the primary swell. At each point of the domain, the spectra can be divided between wind sea and a certain number of swells. The two swells that contain the most energy are designated in order as the primary and secondary swell. Wind, sea and swell parameters can be undefined at some grid points, for the former if there is little wind, for the latter if there are only locally generated waves.

Data in GRIB2 format

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