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
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
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 |
{:.fs-3} † 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 | |
{:.fs-3}
† 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
{:.fs-2}
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
{:.fs-2}
2020-06-26, Ivar Ambjørn Seierstad