Communicating forecast uncertainty from the Met Office convectivescale

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 EX 1 3 PB © Crown copyright Met Office

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

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, highresolution forecasting © Crown copyright Met Office

Met Office ensemble systems Early 2012 MOGREPS-15 • Run at ECMWF • Global • 24 members • To T+15 days • 60 km, 70 levels Global (MOGREPS-G) • 12 members, 6 h update • Products use 24 lagged members • 60 km at mid-lats, 70 levels, to T+72 h • IC and model parameters perturbations Regional (MOGREPS-R) • 12 members, 6 h update • Products use 24 lagged members • 18 km at mid-lats, 70 levels, to T+60 h • IC and model parameters perturbations MOGREPS-UK • 12 members, 6 h update • 2. 2 km, 70 levels • IC perturbations and BC from MOGREPS-R (no high-res perturbations) • Initially to T+6 h on IBM Power 6 • To T+36 h on upgrade to Power 7 © Crown copyright Met Office

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

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

Rainfall products • Derived from 5 min timestep rain rates • Thresholds: any (>0. 2 mm/h), heavy (>4 mm/h), torrential (>16 mm/h) Chance of rain over coming day e. g. chance of torrential (>16 mm/h) rain over period 06: 00 to 00: 00 GMT © Crown copyright Met Office Chance of rain within each hour e. g. chance of torrential (>16 mm/h) rain within each hour Chance of a mostly (very) wet hour e. g. chance of a mostly wet (>0. 2 mm/h) hour MOGREPS-UK 29 th July 03: 00 GMT run

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) Chance >30°C © Crown copyright Met Office Ensemble mean max temp MOGREPS-UK 18 th Aug 03: 00 GMT run

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

Rowing Cosswinds © 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 300 m model were unknown MOGREPS-UK provided confidence • Chance of high temperatures useful 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 © 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 © Crown copyright Met Office

Thanks for listening! © Crown copyright Met Office