1. © Crown copyright Met Office Communicating forecast uncertainty from the Met Office convective-scale ensemble for the London 2012 Olympic Games Andrew Bennett, Caroline Jones, Stephen Moseley, Ken Mylne, Clive Pierce, Nigel Roberts, … Met Office, Fitzroy Road, Exeter EX1 3PB

2. © Crown copyright Met Office Outline Why? How? Products tour Feedback Summary

3. © Crown copyright Met Office Aims Advertise the cutting-edge science being delivered by the Met Office Enhance forecasting guidance by providing a range of scenarios for decision-making Clear-language documentation of the products that everyone can understand Demonstrate the utility of probabilistic, high- resolution forecasting

4. © Crown copyright Met Office Met Office ensemble systems Early 2012 Global (MOGREPS-G) 12 members, 6h update Products use 24 lagged members 60km at mid-lats, 70 levels, to T+72h IC and model parameters perturbations Regional (MOGREPS-R) 12 members, 6h update Products use 24 lagged members 18km at mid-lats, 70 levels, to T+60h IC and model parameters perturbations MOGREPS-15 Run at ECMWF Global 24 members To T+15 days 60km, 70 levels MOGREPS-UK 12 members, 6h update 2.2km, 70 levels IC perturbations and BC from MOGREPS-R (no high-res perturbations) Initially to T+6h on IBM Power6 To T+36h on upgrade to Power7

5. © Crown copyright Met Office Mogreps-UK… Undersampling leaves “holes” of zero-probability where showers could still occur Holes filled in Creation of probability of rain product …with Neighbourhood method Nigel Roberts

6. © Crown copyright Met Office The front page Local time Descriptors Documentation for different audiences

7. © Crown copyright Met Office Rainfall products Chance of rain over coming dayChance of rain within each hour Derived from 5min timestep rain rates Thresholds: any (>0.2 mm/h), heavy (>4 mm/h), torrential (>16mm/h) Chance of a mostly (very) wet hour MOGREPS-UK 29 th July 03:00 GMT run e.g. chance of torrential (>16mm/h) rain over period 06:00 to 00:00 GMT e.g. chance of torrential (>16mm/h) rain within each hour e.g. chance of a mostly wet (>0.2 mm/h) hour

8. © Crown copyright Met Office Temperature products Chance of temperature exceeding 20, 25, 30, 32°C at screen-level – useful for sea breezes Daytime ensemble mean max temperatures All over 12 hours (09:00 to 21:00 GMT) 18 th Aug 2012: hottest day of year (32.4°C recorded in Suffolk) Ensemble mean max temp Chance >30°C MOGREPS-UK 18 th Aug 03:00 GMT run

9. © Crown copyright Met Office Wind products MOGREPS-UK 8 th Aug 21:00 GMT run e.g. chance of light (<6mph) sustained winds at each hour over UK over Weymouth Bay Derived from hourly instantaneous winds at 10m Sustained wind and wind gust Thresholds: strong (> 20mph), light (< 6mph), Beaufort scale (> 12, 17, 29, 23 mph) Areas: Whole UK, Weymouth Bay sailing venue Jim Trice

10. © Crown copyright Met Office Site-specific products 24 Olympic venues: All England Tennis Club Wimbledon Earls Court Excel Greenwich Park Hampton Court Palace Horseguards Parade Hyde Park Lords Cricket Ground North Greenwich Arena Olympic Park The Mall The Royal Artillery Barracks Wembley Arena Wembley Stadium Eton Dorney Weymouth And Portland Brands Hatch Hadleigh Farm Lee Valley White Water Centre City Of Coventry Stadium Millennium Stadium Old Trafford St James Park Hampden Park

11. © Crown copyright Met Office Rowing Cosswinds

12. © Crown copyright Met Office Feedback “The Mogreps-UK products were extremely useful for the Olympic forecasting at Weymouth” – Jim Trice, Met Office Olympic forecaster Assisted use of Weymouth Bay forecasts Characteristics of 300m model were unknown - MOGREPS-UK provided confidence Chance of high temperatures useful for forecasting of sea breezes “I was especially impressed by the variety of products and by the clear explanations that accompanied each of the products.” – Beth Ebert, Research Program Leader, Australian Bureau of Meteorology Over 25,500 web page visits Mean viewing time implies products were being used

13. © Crown copyright Met Office Summary Delivered products from MOGREPS-UK that were Focussed on high-impact weather (high temporal and spatial resolution) Relevant to the general public, Olympic forecasters and LOCOG Presented and documented in an understandable and clear manner to the target audience Showcased cutting-edge science at the Met Office Demonstrated the utility of probabilistic, high resolution forecast products

14. © Crown copyright Met Office Thanks for listening!