Portal:Weather

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Weather is an all-encompassing term used to describe all of the many and varied phenomena that occur in the atmosphere of a planet at a given time. The term usually refers to the activity of these phenomena over short periods of hours or days, as opposed to the term climate, which refers to the average atmospheric conditions over longer periods of time. When used without qualification, "weather" is understood to be the weather of Earth.

Weather most often results from temperature differences from one place to another, caused by the Sun heating areas near the equator more than the poles, or by different areas of the Earth absorbing varying amounts of heat, due to differences in albedo, moisture, and cloud cover. Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure. The resulting pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation causes curvature of the flow via the Coriolis effect. These simple systems can interact, producing more complex systems, and thus other weather phenomena.

The strong temperature contrast between polar and tropical air gives rise to the jet stream. Most weather phenomena in the mid-latitudes are caused by instabilities of the jet stream flow (see baroclinity) or by weather fronts. Weather systems in the tropics are caused by different processes, such as monsoons or organized thunderstorm systems.

Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, while in December it is tilted away, causing yearly changes in the weather known as seasons. In the mid-latitudes, winter weather often includes snow and sleet, while in both the mid-latitudes and most of the tropics, tropical cyclones form in the summer and autumn. Almost all weather phenomena can occur year-round on different parts of the planet, including snow, rain, lightning, and, more rarely, hail and tornadoes.

Related portals: Earth sciences (Atmosphere  · Atmospheric Sciences)  · Tropical cyclones Featured article  · Disasters  · Water

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DustStormInSpearmanTexas19350414.jpg

This dust storm occurred around Spearman, Texas on April 14, 1935. This was in the heart of the Dust Bowl, a period of severe dust storms and drought, which contributed to the Great Depression in the United States.

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Selected article

Subtropical Storm Andrea in May 2007

A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National Hurricane Center in 1972. Subtropical cyclones began to receive names from the official tropical cyclone lists in the Atlantic Basin in 2002.

There are two definitions currently used for subtropical cyclones. Across the north Atlantic and southwest Indian ocean, they require central convection fairly near the center and a warming core in the mid-levels of the troposphere. Across the eastern half of the northern Pacific, they require a mid-tropospheric cyclone to cut off from the main belt of the westerlies and only a weak surface circulation. Subtropical cyclones have broad wind patterns with maximum sustained winds located farther from the center than typical tropical cyclones, and have no weather fronts linked into their center.

Since they form from initially extratropical cyclones which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required for their formation are lower than the tropical cyclone threshold by 3°C (5°F), lying around 23 °C (73 °F). This also means that subtropical cyclones are more likely to form outside the traditional bounds of the hurricane season.

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Did you know...

...that Hurricane Debbie is the only known tropical cyclone ever to strike Ireland?

...that the Tempest Prognosticator, one of the earliest attempts at a weather prediction device, employed live leeches in its operation?

...that eyewall replacement cycles are among the biggest challenges in forecasting tropical cyclone intensity?

...that the Braer Storm of January 1993 is likely the strongest extratropical cyclone ever recorded in the north Atlantic Ocean?

...that in medieval lore, Tempestarii are magicians with the power to control the weather?

...that the omega equation is essential to numerical weather prediction?

Recent and ongoing weather

This week in weather history...

October 11

1846: The Great Havana Hurricane of 1846 killed 163 people in Cuba.

2005: Hurricane Vince made landfall on the Iberian Peninsula as a tropical depression, the only tropical cyclone since the 1800s to do so.

October 12

1634: The Burchardi flood struck the north coast of Germany and Denmark, killing thousands.

1962: The Columbus Day Storm brought damaging winds of more than 100 mph (160 km/h) to a large area of the Pacific Northwest.

1979: The record lowest surface air pressure outside of a tornado, 870 mbar, was measured in the eye of Typhoon Tip.

October 13

1998: Typhoon Zeb reached peak intensity east of the Philippines. Its central pressure was 872 millibars (25.8 inHg), tied for the second-lowest ever recorded.

2006: Lake Storm "Aphid" dumped two feet of incredibly heavy snow on Buffalo, New York, destroying 90% of the city's trees and resulting in 13 deaths.

October 14

1761: The Great Malvern Tornado touched down in the area of Great Malvern, Worcestershire, in England.

1964: Hurricane Isbell made landfall near Everglades City, Florida, causing heavy rain and several tornadoes, as well as killing six people.

2014: A major snowstorm and series of avalanches killed 43 people in Nepal.

October 15

1987: The Great Storm of 1987 hit France and England.

October 16

1975: The first Geostationary Operational Environmental Satellite (GOES-1) was launched to observe cloud patterns, surface temperatures, and other atmospheric trends best viewed from space.

October 17

1091: One of the earliest recorded tornadoes killed two people in London.

1944: A major hurricane struck Isla de la Juventud, Cuba, killing around 300 people.

1998: Heavy rainfall, which would eventually cause severe flooding, began in central Texas, resulting in almost $1 billion (USD) in damage.

Selected biography

Wladimir Peter Köppen

Wladimir Köppen (September 25, 1846 – June 22, 1940) was a Russian born geographer, meteorologist, climatologist and botanist of German descent. After studies in St. Petersburg, he spent the bulk of his life and professional career in Germany and Austria. His most notable contribution to science was the development of the Köppen climate classification system, which, with some modifications, is still commonly used. Köppen was one of the last scholars with a broad enough background and intellectual ability to make significant contributions to several branches of science.

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WikiProject Meteorology is a collaborative effort by dozens of Wikipedians to improve the quality of meteorology- and weather-related articles. If you would like to help, visit the project talk page, and see what needs doing.

WikiProject Severe weather is a similar project specific to articles about severe weather. Their talk page is located here.

WikiProject Tropical cyclones is a daughter project of WikiProject meteorology. The dozens of semi-active members and several full-time members focus on improving Wikipdia's coverage of tropical cyclones.

WikiProject Non-tropical storms is a collaborative project to improve articles related to winter storms, wind storms, and extratropical weather.

Wikipedia is a fully collaborative effort by volunteers. So if you see something you think you can improve, be bold and get to editing! We appreciate any help you can provide!

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