How advances in atmospheric modelling are used for improved flood forecasting. Dr Michaela Bray Cardiff University

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1 How advances in atmospheric modelling are used for improved flood forecasting Dr Michaela Bray Cardiff University

2 Overview of current short term rainfall forecasting Advancements and on going research for short range forecasting Overview of current midrange rainfall forecasting Advancements and on going research for medium range forecasting Future challenges

3 Past Climate Now Hours Days Forecast lead time 1 Week 1 Month Seasonal Decadal Climate Global modelling on all times scales: Analysis of past weather observations to manage climate risks Predicting routine and hazardous weather conditions Monthly to decadal predictions probability of drought, cold hurricanes.. Global and regional climate predictions Agriculture, informs crop choice, planting to yield optimisation and minimise crop failure risk Public, emergency response, international Disaster Risk Reduction Contingency planners, national and international humanitarian response, government and private infrastructure investment Informs mitigation policy and adaptation choices. Impacts on water resources, heat stress crops infrastructure.

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6 Cumbria 2009

7 Flood Guidance Statement (FGS) Flagship product Risk Assessment for all natural sources of flooding (coastal, river, surface water ground water) for a five day period Uses the Reaso a le Worst Case out o e for the i pa t atri FFC are generally responsible for the flood risk assessment for days 3-5 with EA and NRW responsible for days 1-2 Cou t UA ased a d ai l ai ed at a ore Stategic Level

8 Category 1 Responders Category 2 Responders Utilities County Councils Infrastructure

9 Weather Assessment Overnight Consider antecedent conditions Production of FGS A collaborative process Discuss with Chief Issue draft Day shift assessment Gather initial EA/NRW feedback Assess latest model output Strategic FFC input MFDO Telecom final feedback Issue final FGS

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11 Likelihood Overall flood risk Likelihood x Impact Not a simple traffic light system Alignment with NSWWS where possible High Medium Low Very low Flood risk matrix Minimal Minor Significant Severe Potential impacts Overall Flood Risk High Medium Low Very low Likelihood: Very low <20%, low 20%-40%, medium 40%-60%, High >60%

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13 The Surface Water Flood Hazard Impact Model Surface runoff ensemble member time series

14 The Surface Water Flood Hazard Impact Model Top Level Summary of 1km and county level impacts

15 Most likely and worse case scenario might be for several days after the current day. Poor a s Ensemble Met office Global model ECMWF Global model US GSF Global model Each model may show different rainfall accumulations, covering different areas of the UK ranging from very little rain to extensive rain

16 Storm Desmond, Satellite image showing layered precipitable water

17 Past Climate Now Hours Days Forecast lead time 1 Week 1 Month Seasonal Decadal Climate Global modelling on all times scales: Analysis of past weather observations to manage climate risks Predicting routine and hazardous weather conditions Monthly to decadal predictions probability of drought, cold hurricanes.. Global and regional climate predictions Agriculture, informs crop choice, planting to yield optimisation and minimise crop failure risk Public, emergency response, international Disaster Risk Reduction Contingency planners, national and international humanitarian response, government and private infrastructure investment Informs mitigation policy and adaptation choices. Impacts on water resources, heat stress crops infrastructure.

18 Extreme Seasonal Climate Variability Wet Winters Cold Winters Sommerset Levels 2013/2014 Wet Summers Heathrow 2009/2010 Hot/dry Summers Tewksbury 2007 Pontsticill reservoir, drought 1976

19 Risk this coming season Seasonal Forecast: Dependent on current state of global climate variability (ENSO) Will modify the baseline risk Next Decade Expected extreme season from current climate variability Will include unprecedented events. Climate change modified risk Mid century How the risk will change in a warming world.

20 Global Climate model Super computer Observations Forecast

21 Atmosphere Land Surface HadGEM3 -GC2 ocean Atmosphere 60 km global model, coupled with Land surface model Ocean 0.25 degree global model, coupled with Sea Ice model Sea Ice

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24 Winter Extremes Winter 2013/14 Heavy rainfalls caused widespread flooding, power cuts and major disruptions to transport. Winter 2009 Heaviest snowfall for 18 years chaos on roads, railways and airports, schools and businesses closed. Costing the economy an estimated 1.2bn in lost working hours

25 Skillful predictions of winter NAO are possible from one month ahead of winter using model ensemble mean Use a large ensemble (40 members) initialised each year from Potential to give warning to decision makers Scaife et al GRL

26 Summer Extremes Widespread flooding 3.2 billion in property damage EA 2010: "the scale and seriousness of the summer 2007 floods were sufficient to lassif the as a atio al disaster Summer 1976 Summer 2007 Driest UK summer in series back 1910 Severe water shortages Crop failures (~ 500 million) Heath and forest fires Mi ister for Drought a ou ed

27 Summer rainfall Predict summer (JJA) Northern European rainfall Over 58 years ( ) Use 80 ensemble members First significant skill from dynamical model: r=0.47 (p<0.001) Dunstone et al 2016

28 What is the chance of recurrence?

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30 How much data is available? Recent Observations: = 30 cases Met Office Decadal Predictions: x 100 = ~3500 cases Assessment of rare or unprecedented events 100x more data than observations Things that have not yet happened but are physically plausible Seasonal forecasts are started near to true observed state (minimising model biases) Global ocean-atmosphere simulations run freely for many months produce truly new outcomes away from observations

31 Future Challenges Growth of data. In two or three years time, need to handle 60 terabytes of data Expectation of greater accuracy and lead in times Better systems for modelling and verifying impacts Better ways to deal with orographic influences in both short term and longer term forecasting Particularly for accurate rainfall estimates over Wales