© Crown copyright Met Office Communicating forecast uncertainty from the Met Office...

© Crown copyright Met Office

Communicating forecast uncertainty from theMet Office convective-scale ensemble for theLondon 2012 Olympic Games

Andrew Bennett, Caroline Jones, Stephen Moseley, Ken Mylne, Clive Pierce, Nigel Roberts, …Met Office, Fitzroy Road, Exeter EX1 3PB


Outline

• 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, high-resolution forecasting


Met Office ensemble systemsEarly 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


Mogreps-UK…

Undersampling leaves “holes” of zero-probability where showers could still occurHoles filled in

Creation of probability of rain product

…with Neighbourhood methodNigel Roberts


The front page

Local time

Descriptors

Documentation for different audiences


Rainfall products

Chance of rain over coming day Chance 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 29th 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


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)

18th Aug 2012: hottest day of year (32.4°C recorded in Suffolk)

Ensemble mean max temp

Chance >30°C

MOGREPS-UK18th Aug03:00 GMT run


Wind products

MOGREPS-UK 8th 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


Site-specific products

24 Olympic venues:All England Tennis Club WimbledonEarls CourtExcelGreenwich ParkHampton Court PalaceHorseguards ParadeHyde ParkLords Cricket GroundNorth Greenwich ArenaOlympic ParkThe MallThe Royal Artillery BarracksWembley ArenaWembley StadiumEton DorneyWeymouth And PortlandBrands HatchHadleigh FarmLee Valley White Water CentreCity Of Coventry StadiumMillennium StadiumOld TraffordSt James ParkHampden Park


Rowing Cosswinds


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


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


Thanks for listening!

© Crown copyright Met Office Communicating forecast uncertainty from the Met Office...

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