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The Weather portal

Thunderstorm near Garajau, Madeira

Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, "weather" is generally understood to mean the weather of Earth.

Weather is driven by air pressure, temperature and moisture differences between one place and another. These differences can occur due to the sun's angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the largest scale atmospheric circulations: the Hadley Cell, the Ferrel Cell, the Polar Cell, and the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth's surface, temperatures usually range ±40 °C (−40 °F to 100 °F) annually. Over thousands of years, changes in Earth's orbit can affect the amount and distribution of solar energy received by the Earth, thus influencing long-term climate and global climate change.

Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes, as most atmospheric heating is due to contact with the Earth's surface while radiative losses to space are mostly constant. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The Earth's weather system is a chaotic system; as a result, small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to control the weather have occurred throughout history, and there is evidence that human activities such as agriculture and industry have modified weather patterns.

Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies. A star's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind.

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F5 tornado Elie Manitoba 2007.jpg

This tornado struck the town of Elie, Manitoba on June 22, 2007. It was the first tornado outside the United States to be rated F5 on the Fujita Scale, the most severe level of tornado damage.

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Satellite image of Cyclone Orson near peak intensity

Severe Tropical Cyclone Orson was the fourth most intense cyclone ever recorded in the Australian region. Forming out of a tropical low on 17 April 1989, Orson gradually intensified as it tracked towards the west. After attaining Category 5 intensity on 20 April, the storm began to track southward and accelerated. The following day, the cyclone reached its peak intensity with winds of 250 km/h (155 mph 10-minute sustained) and a barometric pressure of 904 hPa (mbar). Orson maintained this intensity for nearly two days before making landfall near Dampier. The cyclone rapidly weakened after landfall as it accelerated to the southeast. After moving into the Great Australian Bight on 24 April, the storm dissipated.

Despite Orson's extreme intensity, damage was relatively minimal as it struck a sparsely populated region of Western Australia. Five people were killed offshore and damages amounted to A$20 million (US$16.8 million). The storm damaged a new gas platform that explored a possible oil field, believed to contain nearly 200 million gallons of oil. The damage delayed the project for nearly two weeks. The most severe impacts took place in Pannawonica, where 70 homes were damaged. Following the storm, clean up costs reached A$5 million (US$4.1 million). Due to the severity of the storm, the name Orson was retired in 1990 and later replaced by Olga.

Recently selected articles: Christmas 1994 nor'easter, Evansville tornado of November 2005, Typhoon Tip, More...

Did you know...

...that the Oklahoma Mesonet is a network of 121 weather instruments across US state of Oklahoma, providing surface weather observations across the state every five minutes?

...that a SIGMET is an advisory issued for airline crews regarding weather that may impact the safety of the aircraft, including atmospheric convection, icing conditions, or even dust storms?

...that the Antarctic Circumpolar Wave is thought by some scientists to be a very slow-moving wave in the atmosphere and ocean of the far southern hemisphere that circles the globe once every 8 years?

...that the Papagayo Jet is a strong wind that often blows across the Gulf of Papagayo west of Central America, sometimes reaching speeds as high as 30 meters per second (110 km/h; 67 mph)?

...that atmospheric optics is the study of different optical phenomena in the atmosphere, including sunsets, rainbows, and sun dogs?

...that the GME was a numerical weather prediction model run by Deutscher Wetterdienst, the German national meteorological service?

Recent and ongoing weather

This week in weather history...

November 10

1979: The SS Edmund Fitzgerald sank during a severe gale on Lake Superior, killing all 29 crew members.

1997: Hurricane Rick made landfall in southern Mexico, the second-latest hurricane ever to do so.

November 11

1940: The Armistice Day Blizzard dumped two or more feet (0.6 meters) of snow on the United States' Midwest, killing 154 people.

November 12

1909: A hurricane made landfall in northwestern Haiti, killing hundreds.

November 13

1984: Hurricane Klaus dissipated in the northern Atlantic Ocean.

November 14

1969: The Saturn V rocket carrying the Apollo 12 mission into space was struck by lightning, nearly causing a mission abort.??????

November 15: Start of the South-West Indian Ocean cyclone season

1989: Dozens were killed in a severe weather outbreak across the eastern half of North America, mainly in the Southeastern and Northeastern United States.

2006: Hurricane Sergio, the strongest Pacific hurricane on record in the month of November, reached its peak intensity, with maximum sustained winds of 110 miles per hour (180 km/h).

November 16

2007: Cyclone Guba reached peak intensity over the Coral Sea. Flooding from the storm's rainbands eventually killed more than 140 people in Papua New Guinea.

Selected biography

Clement Lindley Wragge (September 19, 1852 – December 10, 1922) was a meteorologist born in Stourbridge, Worcestershire, England. After training in law, Wragge became renowned in the field of meteorology, winning the Scottish Meteorological Society's Gold Medal. He set up an extensive network of weather stations around Australia, and was the first to give human names to cyclones. He traveled widely, and in his later years was a reliable authority on Australia, India and the Pacific Islands.

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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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