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InsightsPurpleTRACMTIPodium
Other
Other
  • Weather
  1. Weather
  • Overview
  • Weather Authentication
  • Numerical Weather Prediction
  • Weather Parameters
  • Numerical Weather Prediction
    • Data at a point
      POST
    • Get Weather Parameter Details
      GET
    • Grid data as CSV
      GET
  • Schemas
    • GridCsvRequestBody
    • CoordinateSchema
    • DataAtAPointRequestBody
    • DataAtAPointResponseBody
    • GetWeatherParamsResponseBody
    • ParamValueSchema
    • PositionSchema
    • WeatherParams
  1. Weather

Weather Parameters

The 39 values POST /api/numericalweather/v2/points accepts in weatherParams. Send the name exactly as it appears here: the field is an enumeration, and we reject a name we do not recognise. The same names are the keys of the request body for GET /api/numericalweather/grid/csv.
Twelve of the names end in the unit the value comes back in. SignificantWaveHeightM is metres, Wind10mKnots is knots, PressureMslHpa is hectopascals, Temp2mC is degrees Celsius. A few names, such as CurrentUComponent5Mins, end with a resolution suffix instead of a unit. Most of the remaining names carry neither a unit nor a resolution marker.

Currents#

ParameterMeasures
CurrentSpeedKnotsSurface current speed, in knots
CurrentDirectionSurface current direction
CurrentUComponentEast-west component of the current
CurrentVComponentNorth-south component of the current
CurrentUComponent5MinsEast-west component at 5 minute resolution
CurrentVComponent5MinsNorth-south component at 5 minute resolution
The U and V components describe the same current as CurrentSpeedKnots and CurrentDirection, resolved onto axes instead of as a speed and a bearing. Use whichever form suits your calculation.

Waves and swell#

ParameterMeasures
SignificantWaveHeightMSignificant wave height, in metres
SignificantHeightOfCombinedWavesAndSwellMCombined sea and swell height, in metres
WindWaveHeightMWind-driven wave height, in metres
WindWaveDirectionWind-driven wave direction
MeanPeriodOfWindWavesMean period of wind waves
SignificantHeightOfSwellWavesMSwell height, in metres
DirectionOfSwellWavesSwell direction
PeriodOfSwellWavesSwell period
PrimaryWaveDirectionDirection of the dominant wave system
Wind waves are raised by the local wind; swell has travelled in from elsewhere. A route can meet a low wind wave and a heavy swell at the same time, so we publish both separately alongside the combined figure.

Ice#

ParameterMeasures
IceCoverExtent of ice cover
IceAccretionIce accreted on the vessel
IceGrowthRateRate at which ice is accreting
IceCover is about the water. IceAccretion and IceGrowthRate are about the ship: spray freezing onto the superstructure, which is a stability problem rather than a navigation one.

Wind, temperature and atmosphere#

ParameterMeasures
Wind10mKnotsWind speed at 10 metres, in knots
Wind10mDirWind direction at 10 metres
WindUComponentEast-west component of the wind
WindVComponentNorth-south component of the wind
Temp2mCAir temperature at 2 metres, in degrees Celsius
Temp0mCTemperature at the surface, in degrees Celsius
PressureMslHpaMean sea level pressure, in hectopascals
RelativeHumdityPercentRelative humidity, as a percentage
TotalPrecipitationMmTotal precipitation, in millimetres
TotalCloudCoverPercentTotal cloud cover, as a percentage
VisibilityHorizontal visibility
GeopotentialHeight500mbGeopotential height at the 500 mb level
GeopotentialHeight1000To500mbThickness between the 1000 mb and 500 mb levels
RelativeHumdityPercent is spelled that way on the wire
The parameter name we accept is missing the i in "Humidity". Send it as written here; we reject the corrected spelling.
The two geopotential parameters are upper-air fields rather than surface conditions. Forecasters read the 1000 to 500 mb thickness to judge whether precipitation falls as rain or snow.

Ocean biogeochemistry#

ParameterMeasures
MassConcentrationOfChlorophyllAInSeaWaterChlorophyll-a concentration
MoleConcentrationOfPhytoplanktonExpressedAsCarbonInSeaWaterPhytoplankton, expressed as carbon
MoleConcentrationOfDissolvedMolecularOxygenInSeaWaterDissolved oxygen
MoleConcentrationOfNitrateInSeaWaterNitrate
MoleConcentrationOfPhosphateInSeaWaterPhosphate
MoleConcentrationOfSilicateInSeaWaterSilicate
MoleConcentrationOfDissolvedIronInSeaWaterDissolved iron
NetPrimaryProductionOfBiomassExpressedAsCarbonPerUnitVolumeInSeaWaterNet primary production, as carbon per unit volume
These follow the CF standard-name convention, which is why they read as full sentences. They support environmental and ballast water work rather than navigation.

Units we have not published#

Twelve of the 39 names carry their unit. The other 27 do not, and that includes every direction and every period. Directions are conventionally degrees and periods conventionally seconds. We are confirming a unit for each of them, and this page will carry the full set when we have it.

Related#

Numerical Weather Prediction
How to send these in a request and read the values back.
Weather
What the category covers.
Weather Authentication
The bearer token these endpoints take.
Modified at 2026-10-16 06:01:27
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