September 1999

The month started sunny, very warm or hot in many places but by the 5th and 6th thundery outbreaks were occurring in south-east England and East Anglia. Purley (Surrey) received 30 mm late afternoon on the 5th with local flooding and 'giant' hail which broke windows.

After some rain and wind in north-west areas during the 7th/8th rising pressure allowed mostly sunny and very warn or hot conditions to return by the 10th/11th. Gravesend (Kent) reached 30.4 °C on the 11th the highest September temperature in the UK since 1973.

Thereafter with low pressure not far away remaining days were very unsettled and temperatures declined to near normal. There were frequent outbreaks of thundery rain giving heavy downpours at times which caused flooding in places. East Anglia, south-east and central southern England, the west Midlands and parts of north Wales faired the worst, however there were good sunny periods. Local flooding was reported from east Devon on the 18th, nearby Wilmington (Colyford) collected 51 mm of rain in 3 hours. Presteigne near the Herefordshire / Powys border reported 81 mm in 24 hours ending 09 UTC/19th. Barboume (Worcester) recorded 90 mm from the 18th to 20th while Kenley (Surrey) had 48 mm in 11 hours on the 20th. In central London there was 34 mm of rain between 22 UTC/19th and 16 UTC/20th with a further fall of 18 mm (in less than two hours) on the 22nd during a late afternoon thunderstorm. In Pagham (West Sussex) at about 5 a.m. on the 23rd a tornado caused a £1m trail of destruction, at least 50 dwellings and some vessels in the harbour were badly damaged. On the 25th/26th funnel clouds were seen near the Essex / Suffolk border and off the north Conwy coast respectively. The last week saw much local flooding in north Wales, at Tryweryn (Bala) 85 mm of rain fell in 36 hours (65 mm in 24 hours). Rainfall anomalies ranged from around 116% over north-east England to around 182% in East Anglia.

Central England Temperature (the CET series begins in 1659) The mean value for the month was 15.6 °C which is 2.0 °C above the 1961-90 normal of 13.6 °C, and is in the well above average category. Others: 1961/15.2, 1949/16.3 °C.

England and Wales Rainfall (series begins in 1766) The total for the month was 124.9 mm, which is 160 % of the 1961-90 average, which is in the well above average category. Others: 1995/123.3, 1981/139.9 mm.

England and Wales Sunshine (series begins in 1961) The total for the month was 156.1 hours, which is 118 % of the 1961-90 average, which is in the above average category. Others: 1998/120.4, 1997/155.1, 1991/172.7 hours.