Dr. Jeff Masters' WunderBlog

Europe's cold and snowy winter forecast to gradually ease

Posted by: Dr. Jeff Masters, 05:25 PM GMT del 23 Dicembre 2010

It will be a white Christmas over most of the UK this year, an unusual occurrence in a nation where heavy snows typically occur just a few times per year. High temperatures in London over the past week have averaged about 6°C (11°F) below the average high of 7°C (44°F), and will remain below average through Christmas. Winter has hit Western Europe hard for over a month, with heavy snows significantly disrupting flights all across the continent. For November, the UK saw its heaviest and most widespread snows and coldest temperatures since 1993, and deepest snows since 1965. On Monday, December 20, the temperature plummeted to -18°C (0°F) at Castlederg in Northern Ireland in the UK. According to weather records researcher Maximiliano Herrera, who maintains a comprehensive set of world extreme temperature records on his web site, this beats the previous coldest temperature in Northern Ireland, -17.5°C at Magherally in January 1979. `

Figure 1. Temperatures for Dec. 20, 2010, were wildly different from average over much of the Northern Hemisphere. The British Isles shivered under temperatures 6 - 10°C (11 - 18°F) below average, and Northern Ireland set the record for its coldest temperature ever measured, -18°C (0°F) at Castlederg. At the same time, most of the Arctic had record-breaking temperatures up to 20°C (36°F) above average. Image credit: NOAA/ESRL.

Reasons for the cold weather in Europe
The exceptionally cold weather in Europe is due to a very unusual shift in the atmospheric circulation over the Northern Hemisphere in recent weeks that has allowed cold air to spill out of the Arctic into the mid-latitudes, and warm air to surge northwards into the Arctic. I discussed this Hot Arctic-Cold Continents pattern last week. The Arctic is usually dominated by low pressure and counter-clockwise circulating winds, and this "Arctic Vortex" has broken down and reversed its flow direction to clockwise, as high pressure is now in place over the Pole. Natural variability in the weather can cause this pattern, though significant loss of Arctic sea ice, such as occurred this fall, can also be a contributing factor. The extreme conditions in the Arctic this December has led to a rather remarkable event--sea ice decreased this week, during a period when we normally see some of the fastest rates of ice formation in the Arctic. Arctic sea ice extent is now at its lowest extent ever recorded for this time of year, due to the combined effects of unusual wind patterns and temperatures in excess of 10°C (18°F) above average over most of the Arctic.

Figure 2. The average surface pressure pattern in the Northern Hemisphere on December 20 between 1968 - 1996 (left panel) featured two familiar semi-permanent low pressure systems, the Icelandic Low and the Aleutian Low. Low pressure and counter-clockwise winds dominated the Arctic. But on December 20, 2010 (right panel), surface high pressure dominated the Arctic, and the normal flow of winds reversed from counter-clockwise to clockwise. The Icelandic Low and the Aleutian Low had shifted far to the south. This is an extremely unusual weather pattern for the Northern Hemisphere.

Major atmospheric pattern shift coming
The unseasonably cold weather is due to break in the UK next week, as the atmosphere undergoes a major shift in its circulation. The high pressure region over the Arctic is forecast to break down and be replaced by the usual low pressure region that typically dominates in winter. By New Year's, the Aleutian Low and Icelandic Low should re-establish themselves in their usual locations as the atmosphere reconfigures itself into a more typical pattern, and Europe should have near average to warmer than average temperatures for the first week of 2011.

Jeff Masters

Heathrow Airport Closed By Snow (WurzelDave)

It happend on the day i was due to go to Sweden, this was the view from the window of the aircraft. We were on that plane for about 7 hours not going anywhere, the crew on the SAS 'flight' were great. The company (SAS) put us up in a hotel over night but most at Heathrow were not so lucky! Anyway we were one of only 6 or so flights to fly from Heathrow the following day.

European Snow Madness (richie123098)

Guess we'll just have to keep digging our selves out. Great community spirit round here, we've had tons of snow. 18 inches in total in just a few days but every snowfall we've been out as a community digging us out so we can get to the shops to get our supplies. Might have a true Christmas this year, the shops shelves are empty and have bought hardly any presents. It's going to be a family and church time, celebrating the true meaning of Christmas. Merry Christmas everyone!

The snow must go on ("Queen, Mercury") (anssi47)

One more bike pic :-))

Categories: Winter Weather

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201. bassis 12:49 PM GMT del 24 Dicembre 2010
Merry Christmas Stay Warm Stay Safe Member Since: Settembre 8, 2008 Posts: 0 Comments: 422

202. ShenValleyFlyFish 02:44 PM GMT del 24 Dicembre 2010
Merry Christmas to one an all Member Since: Settembre 9, 2007 Posts: 36 Comments: 4684

203. Orcasystems 02:54 PM GMT del 24 Dicembre 2010
Complete Update Merry Christmas to everyone... and all those others terms that people use at this time of year... I am off to work.. Oh Boy :( Member Since: Ottobre 1, 2007 Posts: 77 Comments: 26077

205. MrstormX 03:09 PM GMT del 24 Dicembre 2010
I hate the new lower case products issued by the nws... Member Since: Maggio 27, 2009 Posts: 0 Comments: 4232

206. ShenValleyFlyFish 03:10 PM GMT del 24 Dicembre 2010
Quoting DudeIBangedYourMom: Blizzard conditions to be felt in NYC and Boston within 72 hours. Snowfall rates from 2-4 feet locally with winds gusting over 90. mph. Take precautions folks, your life depends on it. good post stupid handle Member Since: Settembre 9, 2007 Posts: 36 Comments: 4684

207. Keys99 03:25 PM GMT del 24 Dicembre 2010
More weather facts from the NWS Key West. Is their a 100 year cold weather trend starting to show in the weather records? Have a great Christmas one and all ON THIS DATE IN KEYS WEATHER HISTORY...IN 1876...THE HIGH TEMPERATURE ON CHRISTMAS EVE REACHED 88 IN KEY WEST FOR THE SECOND DAY IN A ROW...PART OF A STRETCH OF FOUR STRAIGHT DAYS...THE 23RD THROUGH 26TH...ON WHICH THAT YEAR STILL HOLDS THE DAILY RECORD FOR HIGH TEMPERATURE. THE 88 READING ON THE 23RD AND 24TH IS THE WARMEST READING EVER RECORDED IN THE MONTH OF DECEMBER...WHICH IS EVEN MORE AMAZING CONSIDERING THAT ON DECEMBER 1ST THROUGH 6TH OF 1876 LOW TEMPERATURES WERE BELOW 50 EVERY DAY...AND ON THE 2ND A READING OF 44 REMAINS TIED FOR THE COLDEST TEMPERATURE EVER RECORDED IN KEY WEST IN THE MONTH OF DECEMBER. THUS BOTH THE WARMEST AND COLDEST TEMPERATURES EVER RECORDED IN DECEMBER BOTH OCCURRED IN 1876. Member Since: Agosto 16, 2007 Posts: 0 Comments: 132

208. hydrus 01:51 AM GMT del 25 Dicembre 2010
...MERRY CHRISTMAS TO ALL.....:) Member Since: Settembre 27, 2007 Posts: 1 Comments: 14312

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