Storm Goretti – the first named storm of the year – hits the UK today and is bringing with it a “weather bomb”.
The phenomenon, also known as explosive cyclogenesis or bomb cyclone, can result in snow and winds strong enough to bring down trees and cause structural damage.
The process has been likened to when ice skaters spin faster by drawing their arms in, according to the Met Office.
What causes a weather bomb?
Sky News weather producer Jo Robinson says a weather bomb is caused by a storm “deepening”.
That’s when the central pressure of a storm drops by 24 millibars [a millibar is a unit of atmospheric pressure] or more over 24 hours, Robinson explained.
In the case of Storm Goretti, it is likely to “deepen close to 40mbs in the 24 hours between midnight Thursday and midnight Friday,” she added.
The Met Office explains that when a rapid acceleration of air caused by the jet stream high up in the atmosphere removes air from the storm column, reducing its weight, it causes pressure to fall at sea level.
This, in turn, sucks in air which converges from surrounding regions – resulting in faster and faster rotation of the circulation.
The resulting winds peak over a period of a few hours and can be strong enough to cause significant damage, the forecaster adds.
How often do they affect the UK?
The UK has experienced numerous weather bombs in the past.
In 2017 Storm Doris moved across the UK, bringing gusts of up to 94mph and heavy snowfall.
Northern England was also hit by a weather bomb in 2014, when waves measuring 52ft high – considered “phenomenal” on the Douglas Sea Scale, which classifies sea conditions – were recorded off the Outer Hebrides.
Gale-force gusts of more than 80mph also struck some northern coastal areas.
Are weather bombs dangerous?
It depends. Sometimes, bomb cyclones behave like conventional winter storms.
But sometimes they produce heavy flooding, blizzard conditions and high wind speeds.
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Daniel Swain, a climate scientist at the University of California, previously told Sky News that much of the danger lies in the fact that a weather bomb can take people by surprise.
He said: “Fundamentally, the impacts of a bomb cyclone are not necessarily different from other strong storm systems, except that the fast strengthening is usually a signature of a very powerful storm system.”
