What is GFS weather model and how it works

What is GFS weather model and how it works


The GFS or GFS27 is one of two major global weather forecast models in the world, on a par with the ECMWF, yet the first one is considered the most common among all models. In other words, if right now you're looking at the weather forecast for the world or your city or region, it's probably from one of these two models.

In this post, you will learn about GFS, its working principle and the main features, and where to find the weather forecast by this model.

What is GFS27 weather forecast model?

The GFS (Global Forecast System) is the most well-known global weather model and it’s updated every six hours produced by the National Centers for Environmental Prediction (NCEP) of the United States National Oceanic and Atmospheric Administration (NOAA).

It is actually made up of 4 separate models which work together to paint an accurate picture of weather conditions: atmospheric, ocean, land/soil and sea ice models.

However, it doesn’t take topography and shapes of coastlines into account, so it isn’t very accurate for places next to bodies of water. Good for oceans.

The official website of the model is Ncdc.noaa.gov.

What are the main features of GFS weather model and how it works?

The GFS model has various resolutions of 27 km. The resolution is the distance between two points of the weather model grid. Bigger resolutions of 50 to 10 km in size are usually deployed in relatively flat terrains, while mountain ranges require the nodes to be a lot closer to each other, usually 5, 2, or 1 km.

The forecast depth of GFS27 weather model is 10 days. The depth of the weather forecast is the number of hours or days for which the forecast is made. As a rule, the lower the depth, the more accurate the forecast.

The GFS forecast step is 1/3 hour(s) depending on the forecast period: 1 h for the first 120 hours (5 days), then 3 hourly for days 5–16. The forecast step is for how long you can see a forecast in the application or on a website. There are two main step types: 1 h and 3 h.

The GFS27 updates frequency is 4 times a day. The update frequency of the forecast is the regular time interval after which new forecast data is received from the supercomputers. There are models like HRRR with 24 times a day updates, but in general, the frequency of the updates of weather models is 1, 2, or rather 4 times a day.

Let's summ up the main features of GFS model:

  • Resolution: 27 km
  • Forecast depth: 10 days
  • Step: 1/3 hour(s)
  • Updates frequency: 4 times a day

Where to get the weather forecast from the GFS model in Windy.app?

The GFS27 weather model is also the main model in Windy.app among 10+ other models. In the app, the model has a the same 27 km resolution. To get a weather forecast:

1. Open your favorite or the nearest spot to your current location in the app from the Home screen or Wind and precipitation map. To see the nearest spots, allow the app to see your location in Settings.



2. Choose GFS27 weather model in the slider under the Wind rose:



3. Read the weather forecast from the GFS for your particular sport or outdoor activity. In Windy.app you can get 15 following weather parameters from the GFS:

  • Wind speed
  • Wind gusts
  • Wind direction (both cardinal and degrees)
  • Air temperature
  • Seal temperature
  • Feels like temperature
  • Bicycle riding temperature
  • Air temperature at the ski resort's bottom and top stations
  • Dew point
  • Clouds
  • Clouds base
  • Precipitation (rain)
  • Snow precipitation
  • Relative humidity
  • Atmospheric pressure at sea level



In addition, you can have the general weatehr conditions: sunny, rainy, cloudy, etc. from the GFS. They are represented by an icon:


Also you can get two charts: the Atmospheric pressure at sea level chart and the Rain and snow chart:


4. Choose or delete one of these weather parameters using the Customization feature. That how you will make your own custom weather profile in Windy.app:



5. Compare weather data from GFS27 model to other models in Windy.app using special Pro feature Compare mode.



6. Compare GFS weather forecast accuracy with other weather models thanks to special Windy.app feature based on data directly from weather stations. The weather stations are always located on the same spot's screen:


7. Return to Wind and precipitation map to see the bigger wind picture in the region from the GFS model.



Text: Windy.app team

Cover photo: Aviv-perets / Unsplash

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