Scotland storm: what is a weather bomb?

Meteorologists use colourful term to describe hurricane-force Scottish weather

BY Tim Edwards LAST UPDATED AT 11:06 ON Fri 9 Dec 2011

EXPERTS have described the hurricane-force storm that lashed Scotland yesterday as a ‘weather bomb’. The evocative language seems appropriate considering the devastation and disruption: power cuts, a wind turbine catching fire, lorries overturned, a blanket warning against travel and the closure of every major bridge in the country.
 
WHAT IS A WEATHER BOMB?
The scientific term for a weather bomb is an ‘explosive deepening’. The phenomenon happens when cold air meets warm air and is characterised by a decrease in atmospheric pressure of at least 24 millibars in 24 hours. The lower the pressure, the stronger the winds become. Yesterday’s storm (see satellite picture above) was accompanied by a drop of 44mb - and gusts of 165mph were recorded.
 
Jonathan Powell, senior forecaster at Positive Weather Solutions, told The Daily Telegraph: “These gusts are really off-the-scale, and surpass hurricane-force. The criteria for what we have seen would fit the weather bomb scenario.”
 
ARE WEATHER BOMBS COMMON?
Weather bombs are more ubiquitous than you might think. The term ‘bomb’ was first coined by meteorologists in the 1940s. The phrase was popularised in 1980 by Fred Sanders, an MIT professor who wrote an article in the Monthly Weather Review. He said ‘bomb’ was appropriate because these systems develop "with a ferocity we rarely, if ever, see over land".
 
WHERE DO THEY OCCUR MOST?
These storms are known to occur in the eastern Pacific off the coast of Asia and the western Pacific. The North Atlantic is particularly prone to weather bombs thanks to the Gulf Stream, which pits a reliable source of warm air against cold. They often lead to severe blizzards in the north-east United States, which are referred to as ‘Nor’easters’.
 
Scotland’s explosive deepening wasn’t the only one in the North Atlantic yesterday. In Nova Scotia, Canada, strong winds tore the roofs off houses and caused power cuts. · 

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