MOGREPS developments and TIGGE Richard Swinbank GIFS-TIGGE meeting March 2014 © Crown copyright Met Office

MOGREPS domains 2013 2.2km grid Up to 36hr 6-hourly update Regional ensemble now stopped 33km grid Up to 72hr 6-hourly update © Crown copyright Met Office 2

MOGREPS – The Met Office ensemble The Met Office Global and Regional Ensemble Prediction System (MOGREPS) is designed to quantify the risks associated with high-impact weather and uncertainties in details of forecasts. 12-member ensemble designed for short-range forecasting Global ensemble run to T+72 at 00, 06, 12 and18 UTC. (N400 ~33 km grid, 70 levels) UK ensemble run to T+36 at 03, 09, 15 and 21 UTC (2.2km, 70 levels ~40km lid) Many probabilistic forecast products are based on a lagged pair of ensemble runs (24 members) 24-member medium-range ensemble – MOGREPS-15 Global ensemble run to T+360 at 00 and 12 UTC, (N216 ~60km grid, 85 levels) Archived in TIGGE dataset Starting point for the storm surge ensemble is our short-range atmospheric ensemble. Describes resolutions applicable to results shown here; planned to upgrade to ~18 km this year with new supercomputer. Analysis uncertainty sampled using Ensemble Transform Kalman Filter, which estimates the impact of observations on the background uncertainty estimated by the previous ensemble run, based on the same maths underlying data assimilation. Aims to produce an ensemble correctly calibrated from T+0, unlike initial growth phase of singular vector perturbation (not perfect in achieving this, of course). Stochastic physics to capture some of the errors associated with model evolution.

Global Ensemble strategy Met Office strategy is to focus on producing forecasts for week 1 with our own MetUM NWP system, and.. Use ECMWF as primary source of forecasts at week 2-4, in combination with GloSea (our coupled seasonal prediction system) and using multi-model ensemble techniques. MOGREPS-G will be extended and MOGREPS-15 will be retired. (It was decided not to implement the earlier proposal to merge MOGREPS-15 and GloSea.)

Changes affecting TIGGE At parallel suite 34 (implementation approx. June 2014): MOGREPS-G and MOGREPS-15 will switch to use improved ENDGAME dynamical core. Extend MOGREPS-G (N400 / 33km) to 7+days (T+174) MOGREPS-G will supply TIGGE archive (NB. We may not be able to produce the full set of current fields, since the method to produce the GRIB2 data feed will change.) In about a year MOGREPS-15 will be retired Once post-processing has been switched to use MOGREPS-G, ECMWF ENS, etc.

Thank-you any questions…? © Crown copyright Met Office