Thundersnow Phenomenon at Lyneham
Reports about the ferocious snowstorm on the 28th January 2004 reveal that it was even more freakish than it first appeared. Arctic air smashed into warmer air so violently that it detonated an explosion of snow, thunder and lightning known as "thundersnow".

Thundersnow also known as a Winter Thunderstorm or a Thunder Snowstorm is a particularly rare meteorological phenomenon that includes the typical behavior of a thunderstorm, but with snow falling as the primary precipitation instead of rain. It commonly falls in regions of strong upward motion within the cold sector of extratropical cyclones between autumn and spring when surface temperatures are most likely to be near or below freezing. Variations exist, such as thundersleet, where the precipitation consists of sleet rather than snow.

That cold front stretched more than 100 miles and, as it marched south, barometer readings dived as air pressure fell and temperatures crashed from about 5°C to -1°C (41°F to 3O°F) in a few minutes.

A massive burst of rain, snow, hall and graupel (snow pellets) fell as blue lightning and cracks of thunder joined in the mayhem: in Bradenstoke electricity power supplies were lost, in South Molton, Devon, lightning punched a hole through the roof of a house. The storm also whipped up winds reaching 70mph a cargo plane at Guernsey airport was spun round 90 degrees, and locally a tree was felled on the A3102 at Goatacre, blocking the main road for a few hours.

These gusts were generated by huge downdraughts as the rain, snow and ice dragged down cold air from the thunderclouds. At the leading edge of the downdraughts, known as the gust front, the winds may have caught small kinks and spun off into "gustnados" (gust-front tornados). Although less powerful than the ordinary tornados, they can still cause damage.

Facts and figures on rain, temperature, pressure humidity and snow, etc., check out our monthly climate page... January 2004