Website URL:
   FREE In Google Play
   Get
   The Weather Company 
   An IBM Watson Business
   undefined___________
   Recently Searched
     * No items to display

   (BUTTON) US°F
   (BUTTON) °F| (BUTTON) °C
   Americas
   Africa
   Asia Pacific
   Europe
   Middle East
   (BUTTON) Toggle Menu
   Weather
     * Today's Forecast
     * Hourly Forecast
     * 10 Day Forecast
     * Monthly Forecast
     * National Forecast
     * National News
     * Almanac

   Radar
     * Weather in Motion®
     * Radar Maps
     * Classic Weather Maps
     * Regional Satellite

   Severe
     * Severe Alerts
     * Safety & Preparedness 
     * Hurricane Central

   Video & Photos
     * Top Stories
     * Video
     * Slideshows
     * Climate News
     * Award-Winning Investigations

   Health & Activities
     * Allergy Tracker
     * Cold & Flu
     * Water Scarcity
     * Boat & Beach Forecast
     * Gardening Forecast
     * Ski Forecast

   TV
     * Watch Live
     * Personalities

   (BUTTON) Toggle Menu
   (BUTTON) °F| (BUTTON) °C
   (BUTTON) US
   Back to Menu
   Americas
   Africa
   Asia Pacific
   Europe
   Middle East
   All sections
   Weather
   Radar
   Severe
   Video & Photos
   Health & Activities
   TV
   

   Next Article

   Australia Smashed Its Hottest Day on Record Two Days in a Row; Catastrophic Fire Danger For Sydney Saturday
   

International News

Bomb Cyclone Storm Dennis, One of the Most Intense North Atlantic Storms on Record, Triggers Massive Flooding in U.K.

By Brian Donegan and Jonathan Erdman

5 days ago

weather.com

   These States Have the Highest Rate of Melanoma From UV Rays
   00:56

These States Have the Highest Rate of Melanoma From UV Rays

   Strong solar UV radiation, poor sun protection and participation in outdoor activities contribute to an increased rate of melanoma in these states.

At a Glance

     * Storm Dennis is hammering Ireland and the U.K. with heavy rain and high winds.
     * Parts of Wales were inundated by severe flooding.
     * Almost 600 flood alerts and warnings were issued in the U.K. Sunday morning.
     * Dennis is a bomb cyclone and rivals the most intense North Atlantic storms in terms of lowest sea-level pressure.
     * It was preceded by another intense bomb cyclone, which battered Iceland with high winds last Friday.

   Storm Dennis lashed the United Kingdom with flooding rain, high winds and battering waves after becoming one of the strongest North Atlantic bomb cyclones on record.

   Sunday morning, just under 600 flood alerts and warnings were in effect in England, the most on record for any day there, according to John Curtin, Executive Director of Flood and Coastal Risk Management of the U.K. Environment Agency.

   Dennis prompted the U.K. Met Office to issue rare code red warnings for heavy rain in parts of southern Wales Sunday morning, where up to 6 inches of rain drenched areas previously swamped by flooding from Storm Ciara last weekend.

   (NEWS: Latest Storm Impacts)

   Among the hardest-hit areas was along the River Taff in Pontypridd, about 10 miles northwest of the Welsh capital of Cardiff, where photos and video showed the river had topped its banks early Sunday. Flooding was also reported along the river in parts of Cardiff.

   Farther north, water from the swollen River Usk also flooded buildings Sunday in Crickhowell, about 25 miles north of Cardiff.

   Severe flood warnings were issued in four locations along the River Teme Sunday.

   Winds gusted as high as 108 mph in Hellisskarð, Iceland, 105 mph over the Scottish highlands, 91 mph in the Welsh town of Aberdaron and 83 mph in northern France.

   If that wasn't enough, thunderstorms in parts of Ireland Sunday afternoon dumped accumulating marble-sized hail.

   Dennis's central pressure plunged 84 millibars in 54 hours, to a low of 920 millibars by Saturday, according to analyses from NOAA's Ocean Prediction Center, easily satisfying the criterion for a bomb cyclone. The lower the pressure, the more intense the storm.

   Dennis became the second-most-intense winter storm in the North Atlantic since records began more than 150 years ago, according to Weather Underground weather historian Christopher Burt and British weather historian Stephen Burt.

   The all-time-lowest pressure on record for a North Atlantic storm was 913 millibars set in January 1993 near Scotland's Shetland Islands. This historic storm broke apart the super oil tanker Braer on a rocky shoal in the Shetland Islands, causing a massive oil spill, Burt noted.
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/Bullets_pressure_comparisons_0.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/Bullets_pressure_comparisons_0.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/Bullets_pressure_comparisons_0.jpg?v=ap&w=980&h=551 800w" >

Historical Sea-Level Pressure Comparisons

   Data from Weather Underground weather historian Christopher Burt and British weather historian Stephen Burt.

   The middle of February is typically the peak of winter storm season in the North Atlantic, and Storm Dennis certainly fit right in.

A Weird Fujiwhara Dance

   Aside from the impressively low surface pressure forecast for Storm Dennis, there were a couple of other fascinating aspects to this.

   First of all, the jet stream disturbance responsible for the development of Dennis was the same one that brought some snow and rain to the eastern United States last Thursday as a part of Winter Storm Mabel.

   Another fascinating aspect to meteorologists was Storm Dennis's interaction with another strong North Atlantic low that preceded it and hammered Iceland last Thursday into early Friday. (We have more details on that first Icelandic storm below.)

   As Dennis intensified, it tracked close enough to the first strong Atlantic low to perform a meteorological dance known as the Fujiwhara effect.

   Named for Dr. Sakuhei Fujiwhara, the meteorologist who first described the phenomenon in 1921, this effect is the rotation of two weather systems around each other in close distance.

   In this case, Dennis and the first storm completed a counterclockwise dance for a time, before the lows merged south of Iceland.
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/storm-dennis-and-twin-sat-13-15feb20.gif?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/storm-dennis-and-twin-sat-13-15feb20.gif?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/storm-dennis-and-twin-sat-13-15feb20.gif?v=ap&w=980&h=551 800w" >

storm-dennis-and-twin-sat-13-15feb20.gif

   Infrared satellite loop from Feb. 13-15, 2020, indicates the twin North Atlantic storms. The first storm, which hammered Iceland on Feb. 14, is labeled by a light blue "1." The second storm, Storm Dennis, is denoted by a bold red "D."

   As meteorologist Jonathan Belles wrote last February about another Fujiwhara case off the U.S. East Coast, these twin lows can either merge, as we expect with Dennis, or can release from each other and go their separate ways.

First Storm Battered Iceland

   Hurricane-force winds were recorded in the first, unnamed storm system in Iceland last Friday.

   The Hafnarfjall weather station, about 20 miles north of Reykjavik, clocked a peak wind gust of 159 mph Friday morning, likely enhanced from nearby terrain. It also clocked gusts above 100 mph for six hours from 6 a.m. to noon local time, according to the Icelandic Met Office.

   Winds along the southern coast of Iceland gusted from 80 to 90 mph Friday and peaked at 95 mph in northwestern Iceland. In the Icelandic capital, Reykjavik, winds gusted up to 70 mph Friday.

   The Icelandic Met Office Thursday issued red alerts for only the second time since 2017 for high winds along the southern and western coasts of Iceland, mentioning some wind gusts along the coast could top 200 kph, or 124 mph, in this first storm. These alerts were downgraded to yellow alerts by early Saturday.

   According to Iceland's Channel 2 and Vísi, one man was injured when a roof was damaged in Hvalfjörour, and wind sensors were knocked out of service due to the ferocity of the winds.

   Late Thursday night, a satellite estimated a wave height of 64 feet several hundred miles west of the Irish coast, whipped up by strong winds from this first storm.

   This storm battering Iceland became a bomb cyclone, with a pressure drop of 67 millibars in 48 hours from an area of low pressure off Nova Scotia just after midnight EST Wednesday morning to a 929-millibar beast near Iceland early Friday morning, according to analyses from NOAA's Ocean Prediction Center.

   The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
   The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

Most Popular

   
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/5dc04cc3-98f8-4ea9-8128-b9589f423123.jpg?v=at&w=1280&h=720" srcset="undefined" >
   
   

Cold or Flu? 9 Ways to Tell the Difference

   
   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/fallallergypromomilenaborsgetty.jpg?v=at&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Which City Is the Worst for Fall Allergies This Year?

   
   
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/924ba717-81b4-44bb-b14b-c85f931dc950.jpeg?v=at&w=1280&h=720" srcset="undefined" >
   
   

How Winter Fashion Has Changed in 100 Years (PHOTOS)

   
   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/ec4134cd-861f-466e-a1aa-d47e095d5df2.jpg?v=at&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Eerie Vintage Photos of People Battling the Flu

   
   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com//util/image/w/061a3f19-07b1-4b75-8edf-75fc14373fcd.jpg?v=at&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Real vs. Fake Christmas Trees: Which is Better for the Environment?

   
   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/gettyimages-152076114_0.jpg?v=at&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Mesmerizing Vintage Photos of U.S. Drug Stores

   
   
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/eshima1.jpeg?v=at&w=1280&h=720" srcset="undefined" >
   
   

World's Weirdest Bridges (PHOTOS)

   
   
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/gettyimages-500503047.jpg?v=at&w=1280&h=720" srcset="undefined" >
   
   

World's Scariest Airport Runways (PHOTOS)

   
   
   <img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/cellphones_0.jpg?v=at&w=1280&h=720" srcset="undefined" >
   
   

The Germiest Public Places

   
   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com//util/image/w/cindy_prim_0623am.jpg?v=at&w=1280&h=720&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Tropical Storm Cindy: Inland Rain and Tornado Maker (RECAP)

   

NBC News Headlines

   
   <img class="styles__noscript__2rw2y" src="https://dsx.weather.com//util/image/w/whale-japan.jpg?v=at&w=320&h=180&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="undefined" >
   
   

Japan To Hunt For 333 Whales

   
   

A Breakthrough For Car Batteries?

   
   

Beijing Smog Reaches New Level

   
   

More Fun for Astronauts?

   
   The Weather Company, an IBM Business; The Weather Channel; Wunderground
     * Feedback
     * Careers
     * Download Apps
     * Press Room
     * Advertise With Us
     * TV

     * Terms of Use
     * Privacy Policy
     * Parental Controls
     * AdChoices 
     * Ad Partners
     * Analytics Partners

     * Georgia Org 
     * This icon serves as a link to download the eSSENTIAL Accessibility assistive technology app for individuals with physical disabilities. It is featured as part of our commitment to diversity and inclusion.

   We recognize our responsibility to use data and technology for good. Take control of your data:
     * Data Rights

   © Copyright TWC Product and Technology LLC 2014, 2020
   Powered by the IBM Cloud