February 13, 1979 windstorm

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Map of the storm. Most of these peak gusts are from official stations Feb131979StormPeakGustMap.jpg
Map of the storm. Most of these peak gusts are from official stations

The February 13, 1979 windstorm is a natural phenomenon that took place on February 13, 1979 in Pacific Canada and the United States. During the early morning of February 13, 1979, an intense wave cyclone moved across southern Vancouver Island, British Columbia. South of the low center, a strong atmospheric pressure gradient was carried across Washington, with associated high winds. With a cold airflow moving toward the northeast interacting with the high terrain of the Olympic Mountains, a lee low developed east of the Olympics. The mesoscale low caused a particularly intense pressure gradient to develop across the Kitsap Peninsula region.

Cyclone large scale air mass that rotates around a strong center of low pressure

In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.

Vancouver Island Island on the western coast of Canada

Vancouver Island is in the northeastern Pacific Ocean. It is part of the Canadian province of British Columbia. The island is 460 kilometres (290 mi) in length, 100 kilometres (62 mi) in width at its widest point, and 32,134 km2 (12,407 sq mi) in area. It is the largest island on the West Coast of the Americas.

British Columbia Province of Canada

British Columbia is the westernmost province of Canada, located between the Pacific Ocean and the Rocky Mountains. With an estimated population of 5.016 million as of 2018, it is Canada's third-most populous province.

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Wind velocity

At 6 mbar over 8 miles, the geostrophic wind potential easily exceeded 200 knots (which roughly translates to about 100 knots in ageostrophic flow over the Earth's rough surface, or 115 mph). As reported by the crew of the Hood Canal Bridge, average winds reached at least 80 mph out of the south, with gusts into the triple digits. These wind velocities were cross-checked on two different anemometers at the bridge control tower.

Hood Canal Bridge floating bridge

The Hood Canal Bridge is a floating bridge in the northwest United States, located in western Washington. It carries State Route 104 across Hood Canal of Puget Sound and connects the Olympic and Kitsap Peninsulas. At 7,869 feet in length, it is the longest floating bridge in the world located in a saltwater tidal basin, and the third longest floating bridge overall. First opened 57 years ago in 1961, it was the second concrete floating bridge constructed in Washington. Since that time, it has become a vital link for local residents, freight haulers, commuters, and recreational travelers. The convenience it provides has had a major impact on economic development, especially in eastern Jefferson County.

Damage

Extensive damage to trees on surrounding private timberland also corroborate the extreme intensity of this tempest. The pressure of wind and wave on the Hood Canal Bridge stressed the structure enough to cause catastrophic failure. It is suspected that a severe list in the bridge exposed pontoon access hatches to the waves, which subsequently tore the covers loose and allowed water to enter the flotation devices, causing sections to sink. It took nearly three years and over $140 million U.S. to rebuild the lost bridge.

See also

Further reading


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