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Locationforecast data model

tags: reference - locationforecast

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 9 km. Air temperature, precipitation and wind speed are further post-processed to better represent local geographical features.

Historical short term forecasts for the Nordic region are available for download from our thredds server. For more information, see the NPW Wiki.

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 in NetCDF format.

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 for this area are not available from our API. A subset of ECMWF real-time forecast data are made available to the public free of charge directly from ECMWF.

Global UV forecasts

Global UV forecasts are provided by Copernicus Atmosphere Monitoring Service .

Variables

The list of variables varies between different models and products. Variables in bold are included in compact.json, others only in complete.json.

Some variables are not available for every geographic area (e.g. outside the Nordic region) or only in the short term forecast, so make sure your client can handle that. Also, some time period aggregations will not always be present if there are insufficient model data.

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.

Instance variables

These are valid for a specific point in time, and can be found under instant.

Name XML tag Unit Description
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_percentile_10   celcius 10th percentile of air temperature (i.e 90% chance it will be above this value)
air_temperature_percentile_90   celcius 90th percentile of air temperature (i.e 10% chance it will be above this value)
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)
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_percentile_10   m/s 10th percentile of wind speed at 10m above the ground (10 min average)
wind_speed_percentile_90   m/s 90th percentile of 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

† not available for long term forecasts (+60 hours)

Period variables

These are aggregations or minima/maxima for a given time period, either the next 1, 6 or 12 hours. Not that next_1_hours is only available in the short range forecast.

Name XML tag Unit Description
air_temperature_max † maxTemperature celsius maximum air temperature over period
air_temperature_min † minTemperature celsius minimum air temperature over period
symbol_code symbol string see WeatherIcon product
precipitation_amount precipitation mm expected precipitation amount for period
precipitation_amount_max @maxvalue mm maximum likely precipitation for period
precipitation_amount_min @minvalue mm minimum likely precipitation for period
probability_of_precipitation   % chance of precipitation during period
probability_of_thunder   % chance of thunder during period

† not available for next_1_hours

Availability

To get an overview of when the various variables are present, check the following examples (x denotes missing variable):

Nordic region forecast

    time                 Variable                          Short range (1 hour steps)               Medium range  (6 hour steps)
-------------  ----------------------------- <---------------------------------------------------><----------------------------->
      instant      air_pressure_at_sea_level ....................................................................................
      instant                air_temperature ....................................................................................
      instant  air_temperature_percentile_10 ....................................................................................
      instant  air_temperature_percentile_90 ....................................................................................
      instant            cloud_area_fraction ....................................................................................
      instant       cloud_area_fraction_high ....................................................................................
      instant        cloud_area_fraction_low ....................................................................................
      instant     cloud_area_fraction_medium ....................................................................................
      instant          dew_point_temperature ....................................................................................
      instant              fog_area_fraction .....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      instant              relative_humidity ....................................................................................
      instant    ultraviolet_index_clear_sky .....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      instant            wind_from_direction ....................................................................................
      instant                     wind_speed ....................................................................................
      instant             wind_speed_of_gust .....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      instant       wind_speed_percentile_10 ....................................................................................
      instant       wind_speed_percentile_90 ....................................................................................
 next_1_hours           precipitation_amount ....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 next_1_hours       precipitation_amount_max ....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 next_1_hours       precipitation_amount_min ....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 next_1_hours   probability_of_precipitation ....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 next_1_hours         probability_of_thunder ....................................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 next_6_hours            air_temperature_max ...............................................xxxxx...............................x
 next_6_hours            air_temperature_min ...............................................xxxxx...............................x
 next_6_hours           precipitation_amount ...............................................xxxxx...............................x
 next_6_hours       precipitation_amount_max ...............................................xxxxx...............................x
 next_6_hours       precipitation_amount_min ...............................................xxxxx...............................x
 next_6_hours   probability_of_precipitation ...............................................xxxxx...............................x
next_12_hours   probability_of_precipitation .........................................xxxxx.xxxxx..............................xx

Global forecast

    time                 Variable                          Short range (1 hour steps)               Medium range  (6 hour steps)
------------  ----------------------------- <--------------------------------------------------------><------------------------>
     instant      air_pressure_at_sea_level ....................................................................................
     instant                air_temperature ....................................................................................
     instant            cloud_area_fraction ....................................................................................
     instant       cloud_area_fraction_high ....................................................................................
     instant        cloud_area_fraction_low ....................................................................................
     instant     cloud_area_fraction_medium ....................................................................................
     instant          dew_point_temperature ....................................................................................
     instant              fog_area_fraction ..........................................................xxxxxxxxxxxxxxxxxxxxxxxxxx
     instant              relative_humidity ....................................................................................
     instant    ultraviolet_index_clear_sky ..........................................................xxxxxxxxxxxxxxxxxxxxxxxxxx
     instant            wind_from_direction ....................................................................................
     instant                     wind_speed ....................................................................................
next_1_hours           precipitation_amount .........................................................xxxxxxxxxxxxxxxxxxxxxxxxxxx
next_6_hours            air_temperature_max ....................................................xxxxx..........................x
next_6_hours            air_temperature_min ....................................................xxxxx..........................x
next_6_hours           precipitation_amount ....................................................xxxxx..........................x
—Ivar Ambjørn Seierstad, 26 June 2020