Medium-range forecasts

Forecasts up to 15 days ahead

Our medium-range forecasts consist of a single forecast (HRES) and our ensemble (ENS) which together give detailed information about the evolution of weather up to 15 days ahead. Forecasts are run from initial conditions valid at 00 and 12 UTC, as well as shorter supplementary forecasts from 06 and 18 UTC. Forecasts become available to users several hours after these times.


HRES is a single forecast (horizontal resolution around 9 km) which provides a description of one possible evolution of the weather out to 10 days ahead.

Find out more about model configurations.


ENS is an ensemble of 51 forecasts with a horizontal resolution of around 9 km. It comprises one control forecast (CNTL) plus 50 forecasts each with slightly altered initial conditions and slightly altered model physics.

ENS is a probabilistic forecast system designed to indicate the range of possible weather conditions out to 15 days ahead, including the probability of occurrence of particular events (such as high winds or heavy rain). The greater the spread of results across the ensemble, the greater the uncertainty in the forecast.

Find out more about how ENS is produced: ENS overview, ENS rationale and construction.

A wide range of forecast variables

As well as atmospheric conditions, our Earth system modelling approach provides forecasts of a range of surface and ocean variables, such as snow depth, soil moisture and ocean waves.