© Crown copyright Met Office Enhanced rainfall services Paul Davies

© Crown copyright Met Office Contents This presentation covers the following areas Lessons learnt following 2007 floods Upgrade to NSWWS. Extreme Rainfall Alerts. Decision making tools Questions.

© Crown copyright Met Office Tewkesbury: 20 th July 2007

© Crown copyright Met Office Gloucester CC Report “That the Meteorological Office and the Environment Agency review their existing Severe Weather Warning and Flood Warning systems in order to incorporate an additional category of the highest risk that is only issued in exceptional circumstances. This would avoid the public and organisations becoming complacent of the significance of the warnings” Extreme warnings

© Crown copyright Met Office Use of probabilities: improvements made to the Met Office NSWWS Enhance web display for “traffic light” alert Differentiate between severe weather and extreme weather events Introduction of routine Severe Weather Advisory

© Crown copyright Met Office Probabilistic forecasting: quantifying uncertainty for risk management 20 th July 2007

© Crown copyright Met Office Example: 20 th July 2007 Tuesday 17 th Wednesday 18 th Thursday 19 th

© Crown copyright Met Office “The nation's current flood defences are focused almost entirely on river and coastal flooding, but about two thirds of last summer's floods were caused by surface water, often following heavy rainfall” Sir Michael Pitt 7 th May 2008 Surface water floods

© Crown copyright Met Office The Pitt Review PITT REVIEW RECOMMENDATION 6 “The Environment Agency and the Met Office should work together, through a joint centre, to improve their technical capability to forecast, model and warn against ALL sources of flooding.”

© Crown copyright Met Office Extreme Rainfall Alert service “A tremendous amount of water came down with very little warning and the surface water drainage couldn't handle it” Somerset Fire Service re heavy rain on Thursday 29 th May 2008

© Crown copyright Met Office Extreme rainfall that could lead to surface water flooding. Accumulation Period (hours) 136 Risk of severe surface water flooding Bromley, London. Flooding depth results using Halcrow surface water model and 30mm/hr rain rates

© Crown copyright Met Office Extreme Rainfall Alert (ERA) Environment Agency - Met Office partnership 6 months trial service to emergency responders since July 2008 Extreme rainfall alerts produced by 24x7 Met Office “wet bench” forecasters supported by Environment Agency, supplemented by bespoke STEPS and time-lagged 4km UK model precipitation products Environment Agency liaison & support facilitated by presence of Agency staff throughout the trial

© Crown copyright Met Office Extreme Rainfall Alert service Cornwall CC reported that a recent alert had let to a pre-emptive deployment of the fire service and as a result they carried out a rescue from a car where floodwaters were rising a foot every 20 minutes.

© Crown copyright Met Office East Anglia – 31 st August 2008 ERA Early Alert issued at 1046 on 31 st August 2008 HR Radar for 1630 on 31 st August 2008 (Black >16mm/hr, clear > 32mm/hr)

© Crown copyright Met Office East Anglia – 31st August North Walsham

© Crown copyright Met Office “the warnings were perhaps not quite specific enough. We had had quite a serious flood in June. We were expecting something on the same scale. What we got was something much, much worse...”. Martin Horwood MP (Cheltenham) Oral Evidence EFRA 12th December 2007 Targeted warnings

© Crown copyright Met Office Wednesday 4 th September 2008 Floods in Barry and North Devon

© Crown copyright Met Office Morpeth floods 6 th September

© Crown copyright Met Office Benefits of increased model resolution. Morpeth floods valid 06UTC Saturday 6 th September km 4km 1.5km The 4km model produced rainfall totals over 100mm of rain in 24 hours in the Morpeth area and over 150mm in 36 hours over the Cheviot hills nearby. These values compare favourably with observations

© Crown copyright Met Office ERA. Probability of exceeding 100mm in the 24-hour period 15 UTC 5th to 15 UTC 6th September from a time-lag ensemble combining UK 4km model forecasts from 03, 09 and 15 UTC 5th September Observed 3 day rainfall totals 4-6 th September

© Crown copyright Met Office Water UK Report “Water companies and Water UK should work closely with the Met Office and the environmental agencies further to develop specific industry requirements for weather information and advanced severe weather warnings and to obtain a better understanding of the potential severity of rain storms that might give rise to large scale flooding events” Decision making tools

© Crown copyright Met Office Working in partnership with other key organisations to develop decision making tools

© Crown copyright Met Office Summary The Met Office has a major programme of investment in improving UK forecasts which is especially focussed on providing better, smaller scale rainfall forecasts. This programme interacts both with the Environment Agency and academic community in developing new science and the end users in addressing real needs. ERA is a good example of the benefits of close joint working Met Office can provide early warning of intense precipitation and future decision making tools

© Crown copyright Met Office Questions and answers

© Crown copyright Met Office Benefits of 4km time lagging z z z

© Crown copyright Met Office Probability of exceeding 100mm in the 24- hour period 15 UTC 5th to 15 UTC 6th September from the UK 4km model Forecast starting at 03 UTC 5th Forecast starting at 09 UTC 5th Forecast starting at 15 UTC 5th