Heavy and thundery downpours developed over north-west England and north Wales around midday, spreading across North Yorkshire through the afternoon. The worst-affected areas were around the North York Moors, with flooding being reported in Helmsley and surrounding areas.
The following information is provisional from both our real-time network and hourly data obtained from the Environment Agency (indicated by a * in table below) on 20 June 2005.
From the station data available, Hawnby (north-west of Helmsley) has reported the most intense rainfall, including just over 50 mm in a 30-minute period.
The Hawnby 3-hour, 1-hour and 30-minute totals all generate return periods in excess of 200 years (using the Flood Estimation Handbook method).
|Hour ending in GMT|
|Hawnby (*)||-||5.8||59.8||3.8||-||69.4 (3 hr)|
|Church Houses (*)||-||0.6||27.0||16.1||0.4||44.1 (4 hr)|
|Topcliffe||0.2||7.4||29.2||3.6||0.0||40.4 (4 hr)|
|Westerdale (*)||-||1.8||27.2||7.0||-||36.0 (3 hr)|
|Brompton, Low Moor (*)||19.0||13.8||0.4||-||-||33.2 (3 hr)|
|Dishforth Airfield||0.0||6.0||16.4||3.0||0.0||25.4 (3 hr)|
|Osmotherley (*)||-||12.0||9.2||1.0||-||22.2 (3 hr)|
|Lockwood (*)||-||1.0||15.8||4.8||-||21.6 (3 hr)|
|Hawarden (N Wales)||30.8||10.8||1.2||0.0||0.0||42.8 (3 hr)|
The UK record for a 30-minute period is 80 mm at Eskdalemuir, Dumfries and Galloway, 26 June 1953.
More-intense rainfalls have been recorded in North Yorkshire. For example, on 10 August 2003 (date that the UK temperature record of 38.5 °C was established), an intense rainstorm was recorded at Carlton-in-Cleveland (North Yorkshire). A total of 49.1 mm was recorded in 15 minutes, 45.9 mm in 10 minutes, 41.3 mm in 8 minutes and 30.0 mm in 5 minutes (information taken from a detailed report produced by the observer at the station, available in 'Weather', Vol. 60, March 2005). Carlton-in-Cleveland, reported 27 mm in 30 minutes during the 19 June 2005 event.
Tip-time data have been received from the Environment Agency for Hawnby, and has been plotted in 5-minute intervals below.
The animation below uses 15-minute, 5 km composite data between 1200 GMT and 1800 GMT.
Initial analysis of 5 km radar data, indicates that some points may have had over 100 mm in just 3 to 4 hours.
Please note: The empirical relationship between radar reflectivity and rainfall rate is fixed whereas in reality this is highly dependent on precipitation type and is very different for rain and hail.