Tornado sightings in Oxfordshire

Tuesday 08th May 2012 by theWeather Club

May Day bank holiday was not only a complete washout for many it also brought a severe thunderstorm, hail and sightings of a tornado in parts of Oxfordshire. The active thunderstorm which developed across Wiltshire during the late afternoon tracked towards Oxfordshire, Buckinghamshire and the south Midlands before dying away.

There were a number of eyewitness reports of heavy downpours and large hailstones causing difficult driving conditions along the A34 during Monday afternoon. Others reported 'extremely high winds' and 'spinning clouds' and video footage and photographs taken at the time clearly show a funnel cloud penetrating down from the main cloud base. Subsequent reports of damage to trees, roof tiles being blown off and smashed windows would suggest that a tornado touched down somewhere near Kidlington in Oxfordshire at around 4pm.

On average in the UK we have around 35 tornado sightings per year; in fact there was a recent sighting in Rugby at the end of April. The size of tornadoes in the UK tends to be much smaller than those that develop in the US because the contrasts in temperature are much greater in the US leading to more active thunder clouds. It is this collision between warm and cold air that causes a large thunder cloud, or cumulonimbus cloud. The warm air is forced upwards while the cold air descends and the cumulonimbus cloud that develops can contain air that rotates. Large downdraughts of air, sometimes associated with heavy rainfall, drag the rotating cloud towards the ground. If this vortex of cloud does not touch the ground it is called a funnel cloud and it is only classified as a tornado when it is in contact with both the ground and the main cloud base.