|
|
|
|
Blizzard
|
| |
|
| |
A blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system; this results in the advection of air from the high pressure zone into the low pressure area.
areas are more likely to experience blizzards than others, but blizzards may occur anywhere there are snow and high winds.
Discussion
Ask a question about 'Blizzard' Start a new discussion about 'Blizzard' Answer questions from other users |
Encyclopedia
A blizzard is a severe winter storm condition characterized by low temperatures, strong winds, and heavy blowing snow. Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system; this results in the advection of air from the high pressure zone into the low pressure area.
Geography
Some areas are more likely to experience blizzards than others, but blizzards may occur anywhere there are snow and high winds. In North America, blizzards are particularly common to the extreme portions of the Northeastern United States, the Northern Great Plains in the United States, Atlantic Canada, and the Canadian Prairie Provinces. Blizzard conditions also occur frequently in the mountain ranges in western North America, however, since these regions are sparsely populated, they are often not reported.
Worldwide, blizzards often occur across Russia, and into the northern reaches of Europe. They have also been known to occur across the United Kingdom, although severe winter storms there are less common due to the maritime influences of the Northern Atlantic Ocean.
Definition
According to Environment Canada, a winter storm must have winds of 40 km/h (25 mph) or more, have snow or blowing snow, visibility less than 500 ft (about 1/10 mile), a wind chill of less than −25 °C (−15 °F), and that all of these conditions must last for 4 hours or more before the storm can be properly called a blizzard.
In the United States, the National Weather Service defines a blizzard as sustained 35mph (56 km/h) winds which lead to blowing snow and cause visibilities of 500ft or less, lasting for at least 3 hours. Temperature is not taken into consideration when issuing a blizzard warning, but the nature of these storms is such that cold air is often present when the other criteria are met. . Temperatures are generally below 0 degrees F.
Other countries, such as the UK, have a lower threshold: the Met Office defines a blizzard as "moderate or heavy snow" combined with a mean wind speed of 30 mph (48 km/h) and visibility below 650 feet (200 m).
When there are blizzard conditions but no snow falling, meteorologists call this a ground blizzard because all the snow is already present at the surface of the earth and is simply being blown by high winds. Ground blizzards require large expanses of open and relatively flat land with a sufficient amount of accumulated and loosely packed, powdery snow to be blown around.
Whiteouts
Although the word is commonly used to describe heavy snow and high winds, this is not a true "whiteout". Real "whiteouts" occur mostly in the Arctic and Antarctic during the spring, when snow is still deep on the ground and there is lots of daylight and surprisingly calm weather and excellent visibility. Whiteouts occur when rays of sunlight are bounced in all directions between bright white clouds, especially a thin layer of overcast and bright snow or ice. Clean snow and ice reflects nearly 85% of incoming light. Falling snowflakes, suspended fog droplets or ice particles in the air would make conditions even worse. In a true whiteout, neither shadows, nearby objects, landmarks, nor clouds are discernible. All sense of direction, depth perception and even of balance may be lost. Land and sky seem to blend, and the horizon disappears into a white nothingness. Whiteouts trick pilots and travelers into believing down is up and thinking far is near.
Economic Impact of Blizzards
Like all severe weather events such as hurricanes,droughts and floods, blizzards are disruptive to local economies. This is especially the case when blizzards hit in localities in generally warmer climates where snow is infrequent. In cities that do not have snow removal equipment, traffic and commerce can be brought to a stand still for days and in some cases weeks. The economic impact ranges across industries, from lost productivity in companies because people cannot get to work, parents must stay home with children due to school closings, airport closures, product delivery delays and the actual cost of snow removal.
See also
External links
|
| |
|
|
