Summer 2007

In June and July 2007 there were major floods in parts of England and Wales when exceptionally large amounts of rain fell in very short periods. We have looked back at what happened, meteorologically, and also at our own forecasts and warnings during both periods.

Our findings highlight very clearly that, overall, for both 24–25 June and 19–20 July we issued accurate forecasts and timely warnings of severe rainfall. However, it must be recognised that accurately forecasting heavy rainfall is only a contribution to the forecast required for actual flooding. Our role was to ensure other organisations such as the Environment Agency were kept informed throughout both events.

Another finding was that being able to use a higher-resolution simulation of the whole of the UK would have provided significantly more useful detail, further ahead, for the areas affected by extreme rainfall, particularly with the July flooding.

June

On Monday 25 June prolonged heavy rainfall resulted in many parts of north and east England being flooded.

Met Office forecast timeline — June 2007
	17–20 June	Localised torrential downpours continued with many Flash warnings issued.
	21 June	News Release issued to highlight unseasonable weather.
	22 June	Early Warning issued to public, government and emergency services giving three days’ notice of potential disruption.
	23 June	Further warnings and update to Early Warning issued for E/NE England.
	24 June	Early Warning updated with highest probabilities for disruption in an arc from Yorkshire and Humberside to the Welsh Borders, with rainfall totals of ‘up to 100 mm or so’.
	25 June	Flash warnings issued for heavy and persistent rain across the high risk areas during the day.

Weather conditions

Days before the actual flooding, the ground around the worst-hit areas became saturated by very heavy rain. Many sites in Yorkshire received at least a month’s rainfall in 24 hours.

On Monday 25th a slow-moving area of low pressure brought a prolonged period of heavy rain to northern and central England. Hitting the already saturated north-east, the water had nowhere else to go and, as a result, led to major flooding.

Figure 1. Surface synoptic analysis map, Monday 25 June at 6 p.m.

Impacts

• Five people died
• Surface water flooding in Hull
• Widespread disruption and damage to more than 7,000 houses and 1,300 businesses in Hull.
• River Don burst its banks, flooding Sheffield and Doncaster
• Flooding in Derbyshire, Lincolnshire and Worcestershire
• Highest official rainfall total was 111 mm at Fylingdales (N Yorkshire). Amateur networks recorded similar totals in the Hull area.
• There were fears that the dam wall at the Ulley Reservoir near Rotherham would burst.

Met Office actions

• Chief Forecaster managed communications to public via BBC and ITV
• Our Operations Centre kept customers, such as the emergency services, informed
• Our Account Managers kept customers, such as the Utilities, informed
• Press release issued and media contacted
• Ministers briefed

A heightened alert state is retained during the week 25–30 June, because of the threat of further rain.

July

The second event caused localised flash flooding across parts of southern England on the morning of 20 July, and later in the day across the Midlands.

Met Office forecast timeline — July 2007
	16 July	Medium-range computer forecast suggests a vigorous weather system could move toward the UK and engage with relatively warm air over northern France.
	18 July	Early Warning issued in the morning, central and eastern areas of England at risk of disruption from 60–90 mm of rain.
	19 July	Risk areas narrowed to south-west Midlands, Gloucestershire and Oxfordshire. Possible rainfall total increased to 75–100 mm.
	20 July	Flash warnings for southern and central England issued before 9 a.m.

Weather conditions

A slow-moving depression centred over south-east England, drawing warm moist air from the continent across the UK. Heavy and slow moving rainfall moved northwards during the day.

Figure 2. Surface synoptic analysis map, Friday 20 July at 12 UTC.

Impacts

• Widespread disruption to the motorway and rail networks.
• In the following days the River Severn and tributaries in Gloucestershire, Worcestershire, Herefordshire, Shropshire broke banks and flooded surrounding areas.
• River Thames and its tributaries in Wiltshire, Oxfordshire, Berkshire and Surrey flooded.
• Flooding in Telford and Wrekin, Staffordshire, Warwickshire and Birmingham
• The highest recorded rainfall total was 157.4 mm in 48 hours at Pershore College (Worcestershire).

Met Office actions

• Met Office Executive Board briefed on 16 July about the chances of this event
• Baroness Young, Chief Executive of the Environment Agency (EA), briefed personally.
• Regular conference calls with Environment Agency, including regional staff
• Attendance at Civil Contingencies meetings at the Cabinet Office Briefing Room (COBR).
• Liaison between Met Office, Environment Agency and Highways Agency press teams and the media were briefed.
• Conferencing with Network Rail
• Development and delivery of a new forecast product for the Environment Agency and the Cabinet Office, giving additional information on rainfall amounts and forecast confidence.