The Unified Model is run operationally, in a number of configurations, for weather forecasting at the Met Office.
A global configuration provides the medium-range weather forecast and also supports the nested higher resolution regional models with boundary data. More detailed short-range forecasts are provided by these high-resolution models which are able to represent certain atmospheric processes more accurately, as well as having a more detailed representation of surface features such as coastlines and orography.
The latest addition is a variable resolution UK model (UKV) which has a high resolution inner domain (1.5 km grid boxes) over the area of forecast interest, separated from a coarser grid (4 km) near the boundaries by a variable resolution transition zone. This variable resolution approach allows the boundaries to be moved further away from the region of interest, reducing unwanted boundary effects on the forecasts.
UK ensemble forecasting systems, supported by a global ensemble, provide information on the uncertainty in short-range forecasts. The solution spread is obtained by perturbing both the initial conditions and also some aspects of the physical processes within the model. A medium-range global ensemble supports probabilistic weather forecasting to two weeks ahead.
|Model||Grid length in mid-latitudes||Grid points||Vertical levels||Forecast length||Run times (UTC)||Initial conditions|
|Global||17 km||1536 x 1152||70|
(lid ~80 km)
(for 00z and 12z)
|00, 06, 12, 18||Hybrid Incremental 4D-Var with MOGREPS Ensemble|
|UKV||1.5 km inner|
4 km outer
|744 x 928||70|
(lid ~40 km)
|36 hours||03, 09, 15, 21||Incremental 3D-Var|
|MOGREPS Global ensemble||33 km||800 x 600||70|
(lid ~80 km)
control member + 11 perturbed members to 7 days
|00, 06, 12, 18||Global analysis + 44 member ETKF perturbations, SKEB and Random Parameters Stochastic Physics, SST and soil-moisture perturbations|
|MOGREPS UK ensemble||2.2 km||532 x 654||70|
(lid ~40 km)
|control member + 11 perturbed members to 36 hours||03, 09, 15, 21||UKV analysis + 11 member perturbations interpolated from global ensemble. Lateral boundary conditions from corresponding global ensemble member.|
The Met Office also has the capability to rapidly relocate regional models to any area of interest worldwide. These Crisis Area Models (CAMs) are run in support of allied military operations and disaster relief.
The weather forecasting configurations of the Unified Model differ from the climate configurations in a number of respects.
Last updated: 23 August 2016