The Wiltshire Hailstorm, 13 July 1967

Abstract

Ludlam 1963) produced a trail of damage across Wiltshire and Gloucestershire caused by violent winds and hailstones up to 3 inches in diameter. This paper gives an account of the storm as revealed by eye witnesses, press reports and radar records and, from an analysis of the prevailing meteorological conditions, discusses the factors likely to have caused its generation. THE STORMJuly 1967 was notable in many parts of England for periods of hot sunny weather with temperatures rising to near 30' C in some areas, but punctuated by violent rainstorms. As will be seen later, one such period of fine weather ended on 13 July with thunderstorms and rainfalls of over 3 inches in 12 hours in some places. In western areas of Wiltshire and neighbouring areas of Somerset and Gloucestershire the heatwave was broken by a violent hailstorm, with hailstones over z inches in diameter and, in some areas, damaging winds. The main areas affected by the storm are shown in Fig I, showing 24-hour rainfall isopleths and locations of severe weather.Aircraft reports a t 1700 GMT showed rapidly developing cumulonimbus over the Somerset-Dorset border with tops at that time approaching 27 ooo ft. By the time the storm reached the Mendips it was producing hail up to half-an-inch in diameterThe main movement of the storm was towards the north-east. Fig. I . Associated weather phenomena

The dust fall and severe storms of 1 July 1968

“…One of these storms developed into a severe travelling storm, of the type described by Browning and Ludlam (1962). The previous severe storm to affect the British Isles was the Wiltshire storm (Hardman 1968) which was an isolated cell. On 1 July 1968, however, the severe storm was bordered north and south by other thunderstorms, but only it produced the large hail shown in Figure 7.…”