White Christmas (weather)

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A white Christmas refers to the presence of snow at Christmas; either Christmas Eve or Christmas Day depending on local tradition. This phenomenon is most common in the northern countries of the Northern Hemisphere. Because December is at the beginning of the Southern Hemisphere summer, white Christmases there are extremely rare, except in Antarctica, in the Southern Alps of New Zealand's South Island, and in parts of the Andes in South America. The Irving Berlin song, "White Christmas", sung by Bing Crosby from the film Holiday Inn, is the best-selling single of all time and speaks nostalgically of a traditional white Christmas.

Definition

White Christmas in Polish Sanok.

The definition of "White Christmas" varies. In most countries, it simply means that the ground is covered by snow at Christmas, but some countries have more strict definitions. In the United States, the official definition of a white Christmas is that there has to be a snow depth of at least 1 in or 2.5 cm at 7:00 a.m. local time on Christmas morning,[1] and in Canada the official definition is that there has to be more than 2 cm (0.79 in) on the ground on Christmas Day.[2] In the United Kingdom, although for many a white Christmas simply means a complete covering of snow on Christmas Day, the official definition by the British Met Office and British bookmakers is for snow to be observed falling, however little, (even if it melts before it reaches the ground) in the 24 hours of 25 December.[3][4] Consequently, according to the Met Office and British bookmakers, even 91 cm (3 ft) of snow on the ground at Christmas, because of a heavy snow fall a few days before, will not constitute a white Christmas, but a few snow flakes mixed with rain will, even if they never reach the ground. In the United Kingdom the most likely place to see snowfall on a Christmas Day is in North and North Eastern Scotland, in Aberdeen, Aberdeenshire or the Highlands.[5]

Although the term 'White Christmas' usually refers to snow, if a significant hail accumulation occurs in an area on Christmas Day, as happened in parts of Melbourne on 25 December 2011, this can also be described as a White Christmas, due to the resulting white appearance of the landscape resembling snow cover.[6]

White Christmases in North America

Canada

In most parts of Canada it is likely to have a white Christmas in most years, except for the coast and southern interior valleys of British Columbia, southern Alberta, southern Ontario, and parts of Atlantic Canada – in those places Christmas without snow is not uncommon in warmer years, with the British Columbia coast the least likely place to have a white Christmas. The definition of a white Christmas in Canada is 2 cm (0.79 in) of snow-cover or more on Christmas morning at 7 am.[7] Environment Canada started to analyze data from 1955 to 2013 for a total of 59 years, It shows the chance of a White Christmas for several Canadian cities.[7]

The year 2006 saw some of the warmest weather on record, with such places as Quebec City experiencing their first green Christmas in recorded history.[8][9][10] In 2008, Canada experienced the first nationwide white Christmas in 37 years, as a series of pre-Christmas storms hit the nation, including the normally rainy BC Pacific coast.[11]

United States

In the United States, there is often – but not always – snow on the ground at Christmas in the northern states, except in the Pacific Northwest, with the northern Plains the most likely to see snow on the ground at Christmas. Some of the least likely white Christmases that have happened include the 2004 Christmas Eve Snowstorm, which brought the first white Christmas in 50 years to New Orleans. The 2004 storm also brought the first measurable snow of any kind since 1895 to Brownsville, Texas, and its twin city of Matamoros, Mexico. The Florida winter storm of 1989 also occurred immediately before Christmas causing a white Christmas for cities like Pensacola and Jacksonville. The same storm buried Wilmington, North Carolina and the rest of Southeastern North Carolina under 38 cm (15 in) of snow.

In the United States the notion of a white Christmas is often associated in the American popular consciousness with a Christmas celebration that includes traditional observances in the company of friends and family. White Christmas is an Irving Berlin song reminiscing about an old-fashioned Christmas setting.

According to research by CDIAC meteorologist Dale Kaiser, the United States during the second half of the 20th century experienced declining frequencies of white Christmases, especially in the northeastern region.[12] The National Climatic Data Center based the probability of a white Christmas (1 in or 2.5 cm of snow on the ground) at selected cities upon the 1988–2005 numbers from stations with at least 25 years of data.[1]

Tables for North America

White Christmases in the United Kingdom

Location Probability[13]
London 6%
Birmingham 15%
Aberporth 9%
Glasgow 35%
Aberdeen 53%
Belfast 22%
Lerwick 75%
Bradford 14% (since 1971)
St Mawgan 10% (since 1957)

In the United Kingdom, white Christmases were more common from the 1550s to the 1850s, during the Little Ice Age; the last frost fair on the River Thames, however, was in the winter of 1813–14.[13] The shift from the Julian to the Gregorian calendar in 1752 also slightly reduced the chance of a white Christmas, effectively moving Christmas earlier in the winter.[14] An "official" white Christmas is defined by the Met Office as "one snowflake to be observed falling in the 24 hours of 25 December somewhere in the UK",[14] but formerly the snow had to be observed at the Met Office building in London.[14] By the newer measure, over half of all years have white Christmases, with snow being observed 38 times in the 54 years to 2015.[14] A more "traditional" idea of snow-covered ground is less common, however, with only 4 occasions in the 51 years to 2015 reporting snow on the ground at 9am at more than 40% of weather stations.[14]

Although most places in the UK do tend to see some snow in the winter, it generally falls in January and February. However white Christmases do occur, on average every 6 years.[13]

Christmas 2009 was a white Christmas in some parts of Britain,[15] with thick lying snow which easterly winds had brought over the previous week. Travel over much of Britain was badly affected by ice and snow on roads, and was made more slippery by partial daytime thaw followed by overnight refreezing. It was the first white Christmas anywhere in the United Kingdom since 2004.[16]

White Christmases in Ireland

In Ireland, the prospect of early winter snow is always remote due to the country's mild and wet climate (snowfall is most common in January and February). Bookmakers offer odds every year for a white Christmas, which is officially lying snow being recorded at 09:00 local time on Christmas Day, and recorded at either Dublin Airport or Cork Airport (bets are offered for each airport). Since 1961, countrywide, snow has fallen on 17 Christmas Days (1961, 1962, 1964, 1966, 1970, 1980, 1984, 1990, 1993, 1995, 1998, 1999, 2000, 2001, 2004, 2009 and 2010), with nine of these having snow lying on the ground at 09:00 (1964, 1970, 1980, 1993, 1995, 1999, 2004, 2009 and 2010). The maximum amount of lying snow ever recorded on Christmas Day was 27 cm (11 in) at Casement Aerodrome in 2010.

At Dublin Airport, there have been 12 Christmas Days with snowfall since 1941 (1950, 1956, 1962, 1964, 1970, 1984, 1990, 1993, 1995, 1999, 2000 and 2004). The statistical likelihood of snow falling on Christmas Day at Dublin Airport is approximately once every 5.9 years. However, the only Christmas Day at the airport ever to have lying snow at 09:00 was 2010 (although no snow actually fell that day), with 20 cm (7.9 in) recorded.[17]

White Christmases in Romania

White Christmases in Romania have been rare in recent times, and they will likely continue so, due to the geographic position of Romania and climate change. In recent years, blizzard and snow falls usually start in January and they usually end at the beginning of March. However, at high altitudes, white Christmases are very common.

Location Probability
Bucharest 75%
Iași 80%
Timişoara 70%
Cluj Napoca 85%
Constanţa 65%
Miercurea Ciuc 90%
Craiova 75%
Braşov 85%
Satu Mare 75%

White Christmases in Poland

White Christmases are becoming rare in Poland. Some northwestern coastal towns barely see White Christmases any more, but they are still relatively common in the northeastern cities of Białystok and Suwałki, as well as in the Tatra Mountains of southern Poland, including the winter capital of Zakopane. The last White Christmas in Kraków was in 2010. Rzeszów had a White Christmas in 2016, the first since 2011.[18]

White Christmases in other parts of Europe

In Europe, snow at Christmas is common in Norway, Sweden, Finland, the Baltic states, Russia, Ukraine, Belarus, and northeastern Poland. In general, due to the influence of the warm Gulf Stream on European climate, chances of a white Christmas are lower the further west. For example, in southern France a white Christmas is very rare, while in Bucharest, Romania, which is at a similar latitude, it is much more likely. Northern Italy and the mountain regions of central-south Italy may also have a white Christmas. In cities such as Turin, Milan or Bologna a Christmas with falling snow or snow on the ground is not a rarity. White Christmases are also common in the Carpathian Mountains, as well as the Alps.

Southern Hemisphere

Because Christmas occurs during the summer in the Southern hemisphere, white Christmases are especially rare events there, apart from Antarctica which is generally uninhabited. In 2006, a snowstorm hit the Snowy Mountains in New South Wales and Victoria, arriving on Christmas Morning and bringing nearly 12 in (30 cm) of snow in higher areas.[19] This was an especially rare event because it occurred during Australia's typically warm summer. In New Zealand's Southern Alps snow can fall any day of the year and a white Christmas is very possible. The same situation can be seen at the Andes at elevations above 4000msl, with some locations on the Bolivian altiplano such as El Alto having the theorical possibility of a white Christmas. A white Christmas in the southern hemisphere (specifically those close to Antarctica) is approximately equivalent to having snow in the northern hemisphere on 25 June, and in some ways is even less likely because the major population centers in the Northern Hemisphere tend to be farther from the equator than those in the Southern Hemisphere.

References

  1. ^ a b "White Christmas?". National Climatic Data Center. National Oceanic and Atmospheric Administration. 20 August 2008. Retrieved 2010-12-25. 
  2. ^ "Chances vary for a white Christmas". CBC News. 24 December 2010. Retrieved 2010-12-25. 
  3. ^ "Will it be a white Christmas?". Met Office. 5 April 2012. Retrieved 2012-11-11. 
  4. ^ "William Hill press release: "£1 Million Riding On A Flake Of Snow!"". Archived from the original on 13 October 2007. Retrieved 2010-12-25. 
  5. ^ Rowley, Martin (26 December 2011). "Meteorology West Moors: Snow at Christmas in the United Kingdom". Retrieved 2010-12-25. 
  6. ^ "Galleries: A White Christmas in Melbourne". Herald Sun. Retrieved 2012-11-11. 
  7. ^ a b "Chances of a White Christmas". Environment and Climate Change Canada. Environment Canada. Retrieved 6 January 2016. 
  8. ^ "White Christmas only in most Canadians' dreams". CBC News. 21 December 2006. Retrieved 2012-11-11. 
  9. ^ "Title unknown". CTV News. Archived from the original on 10 December 2008. Retrieved 2012-11-11. 
  10. ^ "Ontario Weather Review - December 2006". Environment Canada. 3 January 2007. Retrieved 2012-11-11. 
  11. ^ Osorio, Carlos. "Canada has white Christmas". Toronto Star. Toronto Star. Retrieved 6 January 2016. 
  12. ^ Dye, Lee (18 December 2003). "Study: White Christmases Have Become Rare". ABC News. Archived from the original on 10 December 2008. 
  13. ^ a b c "Fact sheet No. 5 – White Christmases" (PDF). National Meteorological Library. Met Office. August 2007. Archived from the original (PDF) on 31 October 2008. Retrieved 13 December 2009. 
  14. ^ a b c d e "Will it be a white Christmas?". Met Office. 10 December 2015. Retrieved 28 August 2017. 
  15. ^ Gammell, Caroline (25 December 2009). "Britain enjoys first white Christmas for five years". The Daily Telegraph. Retrieved 28 August 2017. 
  16. ^ "White Christmas in 2009?". Royal Meteorological Society. 14 December 2009. Retrieved 28 August 2017. 
  17. ^ Met Éireann - Snowfall in Ireland Archived 21 January 2013 at the Wayback Machine.
  18. ^ Super Express (17 December 2014), Boże Narodzenie 2014. Pogoda na święta. Czekają nas białe święta? Sprawdź, gdzie spadnie śnieg. Archived 4 March 2016 at the Wayback Machine. ZPR Media S.A.: Pogodynka Archived 4 March 2016 at the Wayback Machine..
  19. ^ "Aussies celebrate white Christmas. 25 December 2006". ABC News. 25 December 2006. Retrieved 2013-04-03. 

External links

  • Are you dreaming of a white Christmas?
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