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Where does Portal weather and ET data come from?

Where does my weather data come from?

The weather information displayed in the turfRad Portal comes from numerical weather forecast models operated by leading national meteorological agencies, including:

  • NOAA in the United States

  • ECMWF across Europe and globally

  • MeteoSwiss in Switzerland and the Alpine region

  • DWD in Germany and Central Europe

  • Météo-France in France

  • The UK Met Office, MET Norway, KNMI, DMI, Environment and Climate Change Canada, and other national weather services

These forecasts are delivered to turfRad through our integration with Open-Meteo, which automatically selects the highest-resolution suitable forecast model available for the course location.

What resolution is the weather data?

The spatial resolution depends on the location and the forecast period. In the continental United States, near-term forecasts primarily use NOAA's High-Resolution Rapid Refresh—or HRRR—model, which has a grid resolution of approximately 3 km and is updated every hour. For forecast periods beyond the HRRR model's range, NOAA's global GFS model is used at approximately 13 km resolution.

Across Europe, high-resolution regional models are used where available. Examples include:

  • MeteoSwiss ICON-CH: approximately 1–2 km

  • DWD ICON-D2: approximately 2 km

  • Météo-France AROME: approximately 1.5–2.5 km

  • UK Met Office regional model: approximately 2 km

  • MET Norway Nordic model: approximately 1 km

  • KNMI and DMI HARMONIE models: approximately 2 km

  • ECMWF IFS: approximately 9 km for broader European and global coverage

The particular model can change depending on the course location, model coverage, forecast horizon and availability of the latest model run.

Is the weather data coming from the nearest weather station?

No, not from one particular station. The values shown in turfRad are primarily generated by numerical weather-prediction models rather than read directly from one nearby weather station.

Weather models combine observations from many sources including ground stations, weather radar, satellites, aircraft, weather balloons and ocean buoys to estimate atmospheric conditions across a geographic grid.

This provides consistent coverage even where no weather station is located directly on the course. However, an on-course weather station may record different conditions because of very local influences such as terrain, shade, buildings, irrigation and isolated rainfall.

Rainfall is especially variable over short distances. Forecast precipitation should therefore be considered regional guidance and compared with conditions observed on the course, if available.

What does model resolution mean?

A model resolution of 3 km does not mean that the forecast is guaranteed to be accurate within 3 km (1.8 mi). It means that the model represents the atmosphere using grid cells approximately 3 km across.

Conditions inside an individual grid cell can still vary substantially, particularly for thunderstorms, localized showers, wind and temperature in complex terrain.

Where does the ET₀ estimate come from?

Reference evapotranspiration, or ET₀, is calculated from forecast weather conditions using the internationally recognized FAO-56 Penman–Monteith method.

The calculation considers:

  • Air temperature

  • Relative humidity

  • Wind speed

  • Solar radiation

ET₀ represents the estimated water use of a well-watered reference grass surface of 12 cm (~5 in) height. It provides a useful indication of daily evaporative demand but is not a direct measurement of water loss from a specific green or fairway.

Actual turf water requirements can differ because of grass species, mowing height, rooting depth, shade, soil characteristics, plant stress and local management practices.

What is ETc?

Crop evapotranspiration, or ETc, is an estimate of turf water use under standard, well-watered conditions. It is calculated by multiplying ET₀ by a crop coefficient (Kc) which is adjustable in the turfRad Portal Overview tab:

ETc = Kc × ET₀

The Kc value adjusts the reference estimate to better reflect the expected water use of the specific turf surface. ETc provides a practical estimate for irrigation planning but may differ from actual water loss depending on site conditions and plant stress.

Typical textbook values of crop coefficient estimate 0.6 for warm-season turf and 0.8 for cool-season turf. To account for variation between the weather model ET forecast and actual local site conditions, the opimal crop coefficient in the turfRad Portal may have a larger range, e.g. between 0.3 and 1.5.