/Storm Dennis has officially turned into a bomb cyclone

Storm Dennis has officially turned into a bomb cyclone

Forecasters say Storm Dennis has officially developed into a ‘bomb cyclone’.

Devon and Cornwall is already feeling battered and bruised in the wake of Storm Ciara and now we’re bracing ourself for more wet and wild weather.

Multiple Met Office weather warnings are in place over the weekend as Storm Dennis arrives. It’s set to bring winds of up to 60mph and heavy rain that could cause flooding.

Forecasters have now confirmed the storm has undergone “bombogenesis”, officially making it a ‘bomb cyclone’. Here we look at what that means and what we can expect.

What does it mean?

“Bomb cyclone” is a term given to a rapidly strengthening storm and generally the pressure must drop 24 millibars (a unit of pressure) within 24 hours.

High pressure means good weather, and low pressure means bad weather. In a storm, you typically see bands of low pressure belts signalling the storm approach.

Greg Dewhurst from the Met Office told GlasgowLive: “On a slightly more technical definition, it’s called rapid cyclogenesis.

“It’s a low pressure system which drops 24 millibars in 24 hours or more.

“An easier way to think of it is, it’s a low pressure weather system that drops really quickly.”

Storm Dennis is coming

Why is it called a bomb cyclone?

Meteorologists have likened the sudden drop in pressure to a bomb going off as it derives power from the drop in pressure.

When did Storm Dennis become a bomb cyclone?

According to  Accuweather, Storm Dennis developed into a “bomb cyclone” early Thursday, after the central pressure of the storm dropped 1.38 inches of mercury (46mb) in 24 hours.

The drop was recorded from 29.4 to 28.1 inches of mercury (996 mb to 950 mb).

This huge drop in pressure is almost two times more than what is needed to be considered a “bomb cyclone,” which is defined by meteorologists as a pressure drop of 0.71 of an inch of mercury (24 mb) over a 24-hour period.

Terrifying weather map shows the British Isles swallowed up by Storm Dennis
(Image: WXCharts)

What does that mean?

Further strengthening could potentially put Dennis in the running for being one of the most intense North Atlantic storms ever recorded, defined by how low the central pressure of the storm gets.

The top five most intense storms all recorded a pressure of 27 inches of mercury (925.5 mb) or lower.

How will it affect us?

The centre of the storm is likely to stay over Iceland, but Accuweather says it will bring “dangerous winds and flooding” to the hard-hit United Kingdom and northern Europe this weekend.

The Met Office says: “Gales or severe gales and heavy rain throughout the day (Saturday), with the gusts strengthening and extending to eastern parts by the afternoon. Rain particularly heavy across Devon and Cornwall. Maximum temperature 13 °C.

“Remaining unsettled Sunday with further periods of heavy rain and strong winds, but perhaps becoming drier later. Staying windy on Monday and Tuesday, with sunshine and blustery showers.”

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