The main operational model is based on HIRLAM version 4.3 with some minor changes.

SYNOP, SHIP, AMDAR, ACARS, AIREP, SATOB, TEMP/TEMPSHIP, PILOT, SATEM

u, v, F , q

24

OI with a 3-hour cycle. The cycles are refreshed when updated boundary files become available from ECMWF.

Semi-Lagrangian advection

218 x 144 grid points on a 0.297°x 0.297° horizontal Arakawa C-grid, rotated with the south pole at –30° longitude, -30° latitude.

24 levels

Implicit normal mode scheme (2 iterations initializing 4 vertical modes).

A two time level, 3D semi-Lagrangian semi-implicit scheme is used. Time step: 7.5 minutes.

Davies-Källberg relaxation scheme with a cosine-dependent relaxation function applied over a boundary zone of 10 lines. ECMWF boundary fields are used.

Fourth order implicit horizontal diffusion. A time filter is applied to the non-linear terms.

Sundqvist condensation scheme; Savijärvi radiation scheme.

Verification against observations (EWGLAM stations) of temperature, wind and geopotential at standard levels and msl pressure, 2m temperature and 10m winds.

Same as main model but the horizontal grid is 98 x 97 points (0.15° x 0.15°). The nested system has a 1-hour assimilation cycle and uses forecast fields from the main operational model for boundaries. It uses a time step of 225 seconds in the integration scheme.

Main model: 0-48 hour forecast 4 times per day (00, 06, 12 and 18 UTC).

Nested system: 0-3 hour forecasts every hour.

SGI Power Challenge Server with 6 x R10000 (194 MHz) cpus, 512MB memory. The hardware will be replaced this year.