The highest atmospheric pressure ever recorded at Sea-Tac Airport was recorded Wednesday night, KIRO 7 Chief Meteorologist Rebecca Stevenson reports. At midnight, the barometer hit 1043.4 millibars, breaking the previous record of 1043.0 millibars, set on January 28, 1949. The all-time highest atmospheric pressure recorded in Seattle, with records dating back to the late 19th century, was 1043.9 millibars, or 30.83 inches of Mercury. It was recorded in downtown Seattle on December 3, 1921. - KIRO TV

weather map

The high pressure system involved with our record wasn't unusual in that it had a central reading of 1046 mb, only that it was centered much closer to home - just on the Canadian side of the border north of Vancouver. Typically these highs roost over toward the interior of B.C. or western Alberta. That said, our all time lowest pressures are in the fall and winter too, coinciding with strong wind storms. Seattle's all-time lowest pressure recording is 970mb or 28.65″ recorded during the Dec. 12, 1995 windstorm. This amazing high pressure over the Northwest is contributing to the wind problems in the southwest as there is a very large difference in pressure between there and here now. - KOMO News

air pressure chart
Anti-cyclonic Systems: Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the planet's atmosphere. A high-pressure area is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward due to the higher density air near their center and friction with land. The resulting weather system is called an anticyclone. An anticyclone , which is opposite to a cyclone, is a weather phenomenon defined by the United States' National Weather Service's glossary as "a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere. The largest amplitude atmospheric tides are generated by the periodic heating of the atmosphere by the Sun - the atmosphere of Earth is heated during the day by solar radiation. This regular diurnal (daily) cycle in heating generates tides that have periods related to the solar day. Atmospheric Rossby waves are giant meanders in high-altitude winds that have a major influence on the planet's weather. When these loops become very pronounced, they detach the masses of cold, or warm, air that become cyclones and anticyclones and are responsible for day-to-day weather patterns at mid-latitudes. Rossby waves may be partly responsible for the fact that the Northeast United States is somewhat colder than Europe at the same latitudes. Tectonic uplift can also alter atmospheric patterns.

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