Data sources

The data sources for locationforecast are divided into three separate regions. Although the forecasts cover the whole globe, the Nordic and Arctic regions are our main priority. In these regions you will find the most frequently updated and accurate forecasts. All forecasts are automatic. There is no manual editing by meteorologists.

Nordic area

Nordic region

The weather forecasting model for the Nordic area is the MetCoOp Ensemble Prediction System (MEPS). MetCoOp is the Meteorological Cooperation on Operational Numeric Weather Prediction (NWP) between Finnish Meteorological Institute (FMI), MET Norway, Swedish Meteorological and Hydrological Institute (SMHI) and Estonian Weather Service. It provides short term forecasts (0 - 60 hours) and has a horizontal resolution of 2.5 kilometers. More scientific details about this forecasting system can be found here: MEPS article

We also use extensive post-processing to correct for errors in the weather model output caused by unresolved features such as cold pools, inversions, urban heat islands, and an intricate coastline. This is one of the reasons why our forecasts may differ from other forecast providers using MEPS.

Our Nordic forecasts are updated once every hour.

For medium range forecasts (2 - 10 days) the 51 member ensemble forecast from ECMWF is used. It it updated twice pr day. Horizontal resolution is approximately 18 km. Air temperature, precipitation and wind speed are further post-processed to better represent local geographical features.

Historical forecasts short term forecasts for the Nordic region are available for download from our thredds server.

Arctic area

Arctic region

The weather forecasting model used for the Arctic region is the AROME-Arctic weather model. It provides short term forecasts (0 - 60 hours) and the horizontal geographic resolution is 2.5 kilometres. The development of AROME-Arctic is done by MET Norway in collaboration with several national and international projects and institutions. The model system is built on HARMONIE-Arome, a configuration of the ALADIN-HIRLAM NWP system.

Our Arctic forecasts are updated 4 times pr day.

Historical forecasts short term forecasts for the Arctic region are available for download from our thredds server

For medium range forecasts (2 - 10 days) the 51 member ensemble forecast from ECMWF is used. It it updated twice pr day. Horizontal resolution is approximately 18 km.

Rest of the world

The source for our global weather forecasts is the high-resolution weather forecasting model from ECMWF It is used for forecasts from 0 to 10 days. The horizontal geographic resolution is approximately 9 km. Since the resolution is relatively coarse, care should be taken when using particularly the wind speed forecasts in areas with complex topography. It is also recommended to always include elevation information in the query for a location specific forecast. If elevation is not provided, the 1 kilometer resolution global topography GMTED2010 is used instead to adjust the air temperature forecasts. Adjustments are made using a standard adiabatic lapse rate.

Our global forecasts are updated 4 times pr day

Historical forecasts are not available from our API.

Global UV forecasts

Global UV forecasts are provided by Copernicus Atmosphere Monitoring Service .

Variables

Name XML tag Unit Description
symbol_code symbol string see WeatherIcon service
air_pressure_at_sea_level pressure hPa air pressure at sea level
air_temperature temperature celsius air temperature at 2m above the ground
air_temperature_max maxTemperature celsius maximum air temperature over period
air_temperature_min minTemperature celsius minimum air temperature over period
cloud_area_fraction cloudiness % total cloud cover for all heights
cloud_area_fraction_high highClouds % cloud cover higher than 5000m above the ground
cloud_area_fraction_low lowClouds % cloud cover lower than 2000m above the ground
cloud_area_fraction_medium mediumClouds % cloud cover between 2000 and 5000m above the ground
dew_point_temperature dewpointTemperature celsius dew point temperature 2m above the ground
fog_area_fraction fog % amount of surrounding area covered in fog (horizontal view under a 1000 meters)
precipitation_amount precipitation mm expected precipitation amount for period
precipitation_amount_max @maxvalue mm maximum likely precipitation for period
precipitation_amount_min @minvalue mm maximum likely precipitation for period
probability_of_precipitation % chance of precipitation during period
relative_humidity humidity % relative humidity at 2m above the ground
ultraviolet_index_clear_sky 1 ultraviolet index for cloud free conditions, 0 (low) to 11+ (extreme)
wind_from_direction windDirection degrees direction the wind is coming from (0° is north, 90° east, etc.)
wind_speed windSpeed m/s wind speed at 10m above the ground (10 min average)
wind_speed_of_gust windGust m/s maximum gust for period at 10m above the ground. Gust is wind speed averaged over 3s.

Variables in bold are included in compact.json, others only in complete.json. Some variables are not available for every geographic area, so make sure your client can handle that.

The variable names are based on the international CF Standard Name vocabulary, which is mandatory for all governmental scientific institutions under the EU INSPIRE directive.

2020-06-26, Ivar Ambjørn Seierstad