Storm Dennis, monster bomb cyclone, appears to make 'angry face' as it closes in on UK and northern Europe

Courtney Spamer

A monstrous bomb cyclone barreled toward Iceland and the United Kingdom on Friday, threatening a host of extreme weather elements including blizzard conditions and powerful winds.

Storm Dennis, as it was officially named earlier this week, exploded into a bomb cyclone on Thursday after its central pressure plummeted 1.38 inches of mercury (46 mb) in 24 hours. The drop was recorded from 29.4 to 28.1 inches of mercury (996 mb to 950 mb).

This incredible drop in pressure is almost two times greater 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. As the storm began lashing Iceland on Friday, it stirred up terrifying surf, with some swells in the North Atlantic reaching as high as 64 feet over the open ocean. Closer to land, the wave heights topped 40 feet.

The above image shows an infrared satellite view of Dennis as it crosses the Atlantic Ocean on Friday, Feb. 14. (Photo/NASA).

In Iceland's capital of Reykjavik, a 70-mph wind gust was reported around 8 a.m. local time Friday, while farther west of the city, an 89-mph gust was reported in the town of Keflavik.

The storm has the potential to be one of the strongest ever observed over the North Atlantic Ocean. The top-five most intense storms all recorded a pressure of 27 inches of mercury (925.5 mb) or lower.

As Dennis lunged closer to land, an image of the powerhouse storm as shown on the U.S. Global Forecast System, a weather modeling tool, seemed to depict the storm system making an angry face, AccuWeather meteorologist Jesse Ferrell noticed while studying the forecast. The two systems will likely congeal back into one massive storm before clipping the northern islands of the U.K. on Saturday night.

Ferrell said the storm, which he dubbed "Dennis the Menace," essentially split into two storms. He referred to the phenomenon as "double-barreled low pressure." Satellite images on Friday showed heavy precipitation moving over Iceland. Offshore, the storm churned up rough seas, according to the National Weather Service Ocean Prediction Center (OPC). The OPC said it observed a 64.5-foot wave, as estimated by one of its satellites, and wave heights as high as 43 feet closer to land.

StormDennisForecast
The U.S. forecast model shows the storm splitting into two parts, which meteorologists call 'double barrel' low pressure, then coming back together. The purple colors represent lower pressure. (AccuWeather)

Despite the fact that the center of Dennis will likely remain near Iceland, where blizzard conditions were reported on Friday, over the coming days, towering waves are expected across the Northern Atlantic Ocean through the weekend.

"Waves as high as 12-15 meters (40-50 feet) are possible west of the British Isles and south of Ireland as Dennis moves through the region this weekend," said AccuWeather Senior Meteorologist Brett Anderson.

Ships passing through the area should be aware of the storm's track as waves of these heights can be quite dangerous.

These larger waves will even affect the western shores of the British Isles ahead of Dennis' arrival on Saturday. The waves will likely cause coastal flooding and erosion ahead of and through the duration of the storm in western parts of Ireland, Northern Ireland and Scotland.

Higher-than-normal waves are also likely to reach western France.

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Dennis is the fourth-named windstorm of the season and was officially named by weather authorities in Ireland, the U.K. and the Netherlands on Tuesday. Windstorm season in Europe traditionally runs from September through the end of April.

Ireland and the U.K. will be the next to feel the wrath of Storm Dennis on land.

Ahead of the storm, several English Premier League football teams, including Liverpool and Chelsea, announced on Friday that they were considering rescheduling or postponing their matches this weekend, due to the anticipated effects of Storm Dennis.

Wind and rain will increase from western Ireland to South West England and Wales early in the morning on Saturday.

"South-southwesterly wind gusts of 80-96 km/h (50-60 mph) are possible across most of Ireland and the United Kingdom as early as Saturday afternoon and may continue in spurts through the day on Sunday," said AccuWeather Meteorologist Tony Zartman.

This includes major metropolitan areas of London, Manchester and Birmingham in the U.K. as well as Dublin, Ireland.

The strongest winds, which can reach speeds over 100 km/h (62 mph), will likely be reserved for the southwest-facing coasts and the highest elevations of Ireland, Wales and southern England.

The intensity of Dennis has prompted the UK Met Office to issue yellow warnings for wind much of the country through the weekend and into Monday for Northern Ireland and Scotland.

After Ciara barreled through the same area less than a week ago, more gusty winds and rain could lead to another dose of power cuts and major travel disruptions.

Diverted or canceled flights into and out of the United Kingdom area are possible due to the strong winds. Higher-profile vehicles may also have difficulty traveling at higher speeds.

Given the already saturated soil and trees that may already be weakened, additional tree damage and subsequent power cuts are likely, even with less potent wind gusts.

The strongest winds will spread eastward for the second half of the weekend, taking many of the same effects with it through northern Europe.

Increasing winds will be noticeable from northern France through Belgium, the Netherlands and Germany to southern Scandinavia late Saturday, but the strongest winds in these areas will likely hold off until Sunday.

Once again, the windward-facing coasts will have the highest likelihood of experiencing the strongest wind gusts, on the order of 96-112 km/h (60-70 mph).

In addition to the wind, soaking rainfall will accompany Dennis. Widespread rainfall amounts of 12-25 mm (0.5-1 inch) will be possible from the British Isles and northern France to southern Finland.

In the U.K., the Met Office is cautioning that there is a "good chance" some communities could be cut off by flooded roads.

"The highest rainfall totals will likely concentrate across Scotland, Wales, Denmark and Norway, which is typical with a windstorm taking this track," added Zartman.

AccuWeather meteorologists say these areas could receive rainfall amounts of 50-100 mm (2-4 inches).

Even after the core of Dennis has moved on, windy conditions are likely to persist from the Atlantic Coast of France to the Baltic Sea. This could impede power companies and residents alike from having good clean-up weather following the storm.

Cooler air will also follow the storm, increasing the chances of any showery precipitation in higher elevations to fall as snow.

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