'Awful August' — Floods 2008

Major floods were experienced in parts of the UK

'Awful August' was so named by the Met Office because of the unsettled weather it brought to the UK. Rain soaked large swathes of Britain, which was already water-logged by earlier downpours. Our accurate forecasts and warnings enabled people to take appropriate action.

After exceptionally large amounts of rain fell in very short periods there was major flooding in August and September in parts of the UK. Thankfully there were more advanced warnings of the flooding in the form of Extreme Rainfall Alerts from the joint Met Office and Environment Agency Flood Forecasting Centre (FFC). The partnership successfully anticipated a number of flash floods so that drains could be cleared of leaves and other debris, giving the excess rain somewhere to go. Whi le the rainfall on 16 August was capable of causing surface flooding, close consultation with the Environment Agency alerted us to the fact that the problem would be greatly exacerbated by the pre-existing state of the ground and high river levels created by heavy rain throughout the previous days.Most regions of the UK experienced well above-average rainfall in August, with parts of Northern Ireland and eastern Scotland receiving nearly double what they would normally expect. Intense rainfall brought flooding misery to householders across these two regions - with Northern Ireland experiencing its wettest August in a series from 1914.

What we did

  • We issued accurate forecasts and timely warnings of severe rainfall.
  • Working closely with the Environment Agency, which has responsibility for hydrological forecasts, we kept emergency responders informed throughout these events
  • We held ongoing conferences held with the various Gold Commands (emergency centres) during the events.
  • Media and Government departments were kept well-briefed.
  • Warnings were communicated well in advance to our customers and the public.
  • In September a press release was issued.

What happened in August

On 16 August prolonged heavy rainfall led to many areas in Northern Ireland being flooded.

Warning map for Saturday, 16 August 2008 Warning map for Saturday, 16 August 2008
Event timeline - August
DatesActions
14 AugAdvisories of a moderate risk of a severe weather on Saturday 16 Aug, issued via website
15 AugAdvisories upgraded to early warning of severe weather, up to 60 mm of rain in places.Public Weather Service advisor in Northern Ireland held a teleconference with emergency planners and local authorities.
16 Aug, amRelevant agencies informed by text message that there was significant risk of surface flooding in eastern parts of Northern Ireland during Saturday afternoon and evening.
16 Aug, 3pmFlash warnings, including the risk of flooding, issued, valid until 6pm.
16 Aug, 5.30pmFlash warning extended to 10 p.m. for County Antrim and County Down.

Synoptic analysis chart, Sat 16 August at 1200 UTC Synoptic analysis chart, Sat 16 August at 1200 UTC

Weather conditions

The start of August had been very wet. In the week preceding the heavy rainfall of 16 August parts of Northern Ireland, and Scotland, had localised flooding. Some areas in Northern Ireland recorded their monthly rainfall averages - around 70 to 80 mm or three inches - between 11-15 August.Surface flooding had already resulted in road closures during 12 August. Further heavy and locally thundery downpours occurred on nearly every day during the week of 11-15. This had all resulted in the ground being saturated and river levels being high.On 16 August a slow-moving frontal system brought torrential rainfall as it north-east across Northern Ireland.

Impacts

  • More than two inches (55-65 mm) of rain fell widely across many central and eastern parts of Northern Ireland.
  • Highest official rainfall total was 74.8 mm (three inches) at Portglenone (Ballymena) in 12 hours - a one-in-90-year event. An unofficial rain gauge in Ballyclare Co. Antrim recorded a 24-hour total of 88.9 mm (three-and-a-half inches) - a one-in-150-year event.
  • Widespread disruption included 37 road closures, a train derailment and collapsed bridges.
  • A newly opened underpass in Belfast was completely filled with flood water - up to 15 feet deep at times. Government departments were briefed.

What happened in September

Heavy rainfall between 5 and 7 September resulted in many parts of England and Wales being flooded.

Radar image for 5 September Radar image for 5 September
Event timeline - September
DatesActions
31 AugFirst indication in medium-range guidance of large rainfall totals on Friday 5 September, focused on SW England and Wales.
2 SeptAdvisory for heavy rain for SW England, Wales and central southern England issued via website.
3 SeptEarly Warning for heavy rain on Friday in SW England, Wales and parts of central southern England issued. Advisory for heavy rain for NE England issued via website.
4 Sept (am)Early Warning for heavy rain updated, 80% risk of disruption to south-western parts of the UK, issued to agencies in south Wales. Early Warning issued for NE England for Saturday. Advisories issued for other areas. Totals expected to exceed 50 mm (two inches) in places.
4 Sept (pm)Early warning for SW UK upgraded to Flash warning and extended to other areas.
6 SeptFlash warnings issued for more than 60 mm in part of the UK, across the high risk areas during the day.

Weather conditions

An area of low pressure that moved north-eastwards across the UK on 5 and 6 Sept brought prolonged heavy rainfall to many areas, especially south-west England, Wales, south-west Midlands and north-east England. The event was in two clear phases. The early phase was from a combination of frontal and convective rainfall, which affected Wales and part of south-west England on Friday. The second phase took place on Saturday/early Sunday over Northumberland due to very prolonged heavy frontal rainfall, driven in on a strong north-easterly wind.

Impacts

  • Widespread disruption and more than 1,000 homes damaged - particularly in south Wales and Northumberland.
  • River Wansbeck burst its banks, flooding Morpeth.
  • Train services in Wales disrupted because of a landslip.
  • Liscombe, Somerset recorded 74.6 mm (almost three inches) in 24 hours on 5 Sept, more than a month's rainfall.
  • Albemarle, Northumberland recorded 112.0 mm (four-and-a-half inches) in the 72 hours from 09:00, 4 Sept to 09:00, 6 Sept, most falling in 48 hours.

The result

  • The Met Office's short-range ensemble prediction system, known as MOGREPS, provided exceptionally good guidance of both the amounts of rain and the location of the area most at risk during the September event.
  • MOGREPS is designed to provide risk assessment and uncertainty information for the short-range forecast in the first two days, with particular interest in severe, high-impact weather.
  • As well as predicting high probabilities of heavy rain in south-west England and south Wales, MOGREPS pinpointed the area just inland of the coast in north-east England and south-west Scotland, close to the town Morpeth, as having the highest chance of significant rainfall; more than 20 mm in six hours.

The future

  • Looking back on what was the wettest Northern Ireland experiencing its wettest August in a series from 1914, individual endeavour, strong teamwork, consistent messages and Flood Forecasting Centre (FFC) procedures worked well.
  • The response gave positive signs for the future, with potential for further integrating the science, technology, people and services of the FFC.

Last updated: 3 June 2011