GFS forecasts - info

Last update: March 2017

    Data description Inputs - Outputs - Automatic access

   Please note that the service is not yet available...


Data description

The Global Forecast System (GFS) is a weather forecast model produced by the National Centers for Environmental Prediction (NCEP). Dozens of atmospheric and land-soil variables are available worldwide, among which we selected a few parameters as listed in "output variables".

This service delivers the most recent spatial resolution of 0.25°, corresponding approximately to 28 km.

The GFS archive 0.5° model Cycle Runtime (CR) is 0 h, 6 h, 12 h, and 18 h. Are also provided to the users the forecasts computed at CR+3 h to finally deliver time series with a 3 hour time step.
For the current day, the most recent computed CR and the corresponding CR + 3 h will be given. Afterwards, only 3 h forecasts will be given.

  • Provider: NCEP (ncdc.noaa.gov/data-access/model-data/model-datasets/global-forcast-system-gfs)
  • Spatial coverage: worldwide
  • Spatial resolution: 0.25° (approx. 28 km)
  • Temporal coverage: current day "d" up to "d+7"
  • Outputs parameters: Temperature in Kelvins (at 2 m above ground), Relative Humidity in % (at 2 m), Pressure in hPa (at 2 m), Wind speed in m/s and direction in degrees (at 10 m), Rainfall, Snowfall and Snow depth
  • Time step: 1 day, 3 hours, 1 h, 15 min, 10 min, 5 min and 1 min. Please note that original time step of data is 3 hours. As a consequence, below 3 hours received data result from an interpolation
  • Missing data: -999
  • Access:
    • FREE and UNLIMITED manual access via the interface.
    • FOR PAY: an annual subscription fee is applied to automatically access the GFS data to maintain the servers. Don't hesitate to contact us to ask for a quotation.
  • Remarks:

    • for a given location results from a bilinear interpolation of the values of the 4 closest GFS pixels. Original time step is the hour.
    • No altitude correction applied to the meteorological parameters retrieved by using this service.
    • Wind speed and direction are not directly provided by GFS, but computed from the "u" and "v" vectors of wind speed. As the formula are not linear, please note that the monthly (or daily) values computed from the hourly values of wind speed are different from the monthly values retrieved from the interface.
    • Same remark for the relative humidity parameter, computed with a non-linear expression from pressure, temperature and specific humidity.
    • Other variables (pressure and temperature) are linear.
    • For values with a time step below the hour, the hypothesis corresponds to the end of the interval.

Inputs

  • Latitude and longitude: enter the values in decimal degrees, or directly click on the map to select your point, or you can also use the "Search Address" tool on the top of the map.
  • Start date and End date: format yyyy-mm-dd. Please pay attention to ask for complete months when asking for monthly values. If incomplete, the given monthly value results from an interpolation based on the selected days.
  • Time step: 1 day, 3 hours, 1 h, 15 min, 10 min, 5 min and 1 min
  • Output format: CSV only

Outputs

The output file format is CSV. Right click on the link to retrieve your file.

  • Temperature: temperature at 2 m above ground in Kelvins (K)
  • Relative humidity: Relative humidity at 2 m above ground in percent (%)
  • Pressure: Pressure at ground level in hPa
  • Wind speed: Wind speed at 10 m above ground in m/s
  • Wind direction: Wind direction at 10 m above ground in degrees (0 means from North, 90 from East...)
  • Rainfall: Rainfall in kg/m2 (Rain depth in cm can be obtained by dividing the values by 10)
  • Snowfall: Snowfall in kg/m2
  • Snow depth: Snow depth in meters

Automatic access

Even if the data are for free, we need to dimension our servers to welcome the large number of automatic requests. A fee is thus applied depending on the number of time series retrieved every day / month. Please for a quotation.

Request (Unix and Windows): permanent access on Carpentras (44.083°, 5.059°), France
wget -O SoDa_GFS-Forecasts_Carpentras.csv --header="soda-user: guest" --header=soda-passwd: guest" ...
"http://www.soda-is.com/pub/GFS-forecasts_request.php?geopoint=44.083,5.059&firstday=2017-01-01& ...
lastday=2017-01-05&duration=h"

More information on the automatic access (for inputs similar to HelioClim-3)

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