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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 |
