Heavy rainfall early September 2008
Prolonged rainfall resulted in flooding, especially in south Wales and north-east England...
An area of low pressure that moved slowly north-eastwards across the UK 5-6 September brought prolonged heavy rainfall to many areas, notably south-west England, Wales, the south-west Midlands and north-east England.
Synoptic situation at 1200 on 5 September
Synoptic situation at 1200 on 6 September
Shown below are the rainfall rates detected by the rainfall-radar network at 1200 on 5 September and at 1200 on 6 September showing how the widespread rain on the 5th had become mainly confined to north-east England on the 6th.
Twenty-four-hour totals in excess of 40 mm were reported widely from 0900/5th to 0900/6th and places in north-east England recorded over 100 mm in the 48-hour period 0900/5th to 0900/7th with a few totals over 150 mm. The totals for the three 'rainfall days' 4th, 5th and 6th (0900/4th to 0900/7th) are shown below.
Provisional 3-day rainfall totals
This rainfall followed well above average rainfall in August and an unsettled start to September. On the 5th, there was flooding of homes and businesses and transport disruption across parts of the south-west Midlands, south and mid Wales, particularly the south Wales valleys. On the 6th flooding affected north-east England, where the town of Morpeth in Northumberland was badly hit with some 1000 properties flooded.
The table below shows a selection of the rainfalls recorded on each of the rainfall days 4th, 5th and 6th with return periods for the highest 48-hour totals. The 3-day totals represent 50-100% of the September monthly average (for 1971-2000) in Wales and western England but 150-300% in parts of north-east England. The daily total of 80.7 mm at Morpeth (Cockle Park) on 5th is the highest recorded there in a record that begins in 1897, the previous record being 77.9 mm on 26 October 1900.
|Weather station||Rainfall on 4th (mm)||Rainfall on 5th (mm)||Rainfall on 6th (mm)||Rainfall total 4th-6th (mm)||Return period (years)#||Percent of Sep average (%)|
|Chillingham Barns, Northumberland||0||76.2||82.1||158.3||>200||290|
|Capel Curig, Conwy||22.6||49.6||37.4||109.6||<1||48|
|Nunraw Abbey, E Lothian||0||62.3||18.5||80.8||<5||111|
|Emley Moor, W Yorkshire||6.5||46.8||19.8||73.1||<10||116|
|Fylingdales, N Yorkshire||N/A||60.1||2.4||62.5||-||77|
|St Athan, Glamorgan||7.4||33.0||4.8||45.2||<1||44|
# Return periods for highest 48-hour totals
This initial summary is based upon the data available so far and will be updated once values from the full network are received and checked.