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The 2014–15 North American winter refers to winter in North America as it occurred across the North American continent from late 2014 through early 2015. While there is no well-agreed-upon date used to indicate the start of winter in the Northern Hemisphere, there are two definitions of winter which may be used. Based on the astronomical definition, winter begins at the winter solstice, which in 2014 occurred on December 21, and ends at the March equinox, which in 2015 occurred on March 20. Based on the meteorological definition, the first day of winter is December 1 and the last day February 28. Both definitions involve a period of approximately three months, with some variability. While both the meteorological and astronomical definitions of winter involve the onset of winter occurring in December, many places in North America experienced their first wintry weather during mid November. A period of below-average temperatures affected much of the contiguous United States, and several records were broken. An early trace of snowfall was recorded in Arkansas. There were greater accumulations of snow across parts of Oklahoma as well. A quasi-permanent phenomenon referred to as the polar vortex may have been partly responsible for the cold weather. Temperatures in much of the United States dropped below average by November 19 following a southward "dip" of the polar vortex into the eastern two-thirds of the country. The effects of this dip were widespread, bringing about temperatures as low as in Pensacola, Florida. Following a significant snowstorm there, Buffalo, New York received several feet of snow from November 17–21. During the 2014–15 winter season, Boston broke its all-time official seasonal snowfall record from the winter of 1995–96, with a total snowfall record of as of March 15, 2015. Many records for snowfall and temperature were broken, many for the month of February, with every state east of the Mississippi River being colder than average, some for the entire winter. However, this meteorological winter was the 19th-warmest of the past 120 winters over the Lower 48 states, largely due to persistent warm weather in the West. == Seasonal forecasts == On October 16, 2014, the National Oceanic and Atmospheric Administration's Climate Prediction Center issued its U.S. Winter Outlook. This outlook indicated that below-average temperatures in parts of the south-central and southeastern United States would be favored, with above-average temperatures favored in the western U.S., Alaska, Hawaii, and New England. Drought conditions were expected to improve in California's southern and northwestern regions, but no improvements were expected earlier than December or January. Above-average conditions were also expected to pervade the winter months in the western U.S., the Intermountain West extending across the U.S.–Canada border through New York and New England, and Alaska and Hawaii. The Precipitation Outlook favored above-average precipitation across the southern tier and Atlantic coast of the United States, with above-average precipitation also favored in southern Alaska and the Alaska panhandle. Below-average precipitation was favored in Hawaii, the northwestern United States, and near the Great Lakes region. The rest of the country was given an "equal chance" for either above or below average temperatures and/or precipitation. On November 30, 2014, Environment Canada's monthly prediction system produced a forecast for the months of December, January, and February across Canada. Areas in and just off the western coast of British Columbia were considered the most likely areas for above-average temperatures. Other areas where above-average temperatures were favored by the forecast included Yukon, the Northwest Territories, northern parts of Alberta and Saskatchewan, and northwestern parts of Manitoba. Below-average temperatures were favored in and near Lake Superior in Ontario, across much of Hudson Bay, in far-eastern parts of Nunavut, and in northern parts of Quebec. The most favorable locations for above-average precipitation were northwestern British Columbia, southwestern Yukon, eastern parts of the Northwest Territories, western parts of Nunavut, and Newfoundland. The most favorable areas for below-average precipitation were southeastern British Columbia, southern Alberta, southern Saskatchewan, some northern parts of Quebec, and an isolated spot in the northern half of Nunavut. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「2014–15 North American winter」の詳細全文を読む スポンサード リンク
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