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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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Moore Oklahoma Tornado Damage.jpg

A pickup truck was wrapped around this utility pole by the extreme winds from the Moore, Oklahoma tornado which occurred on 1999-05-03. The truck was then pummelled by winds which exceeded 200 mph (320 km/h), stripping most of the sheet metal off the truck. The F5 tornado was one of the most severe ever observed, and destroyed more than 1500 homes, killing 36 people.

Recently selected pictures: Spearman, Texas dust storm, Cordell, Oklahoma tornado, Mammatus clouds, More...

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Ice Storm 98 trees line Noaa6198.jpg

The Ice Storm of 1998 (also known as Ice Storm '98) was a massive ice storm that struck areas of Eastern Ontario, southern Québec, and Nova Scotia in Canada, and bordering areas from Northern New York to Northern Maine in the United States. From January 4-10, 1998, up to 5 inches (120 mm) of ice accumulated on surfaces in these areas due to an unusually long period of freezing rain. The tremendous weight of ice accretion caused massive damage to trees and electrical infrastructure all over the area, leading to widespread power outages. Millions were left without power for periods varying from days to weeks, leading to more than 30 fatalities, a shut down of activities in large cities like Montreal and Ottawa, and an unprecedented reconstruction of the power grid. More than $5 million in damages were attributed to this storm.

1998 Ice Storm map.png

Did you know...

...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?

...that a consistent thunderstorm that forms over the Tiwi Islands of Australia is given the name Hector by local residents and pilots?

Recent and ongoing weather

This week in weather history...

May 22

1951: Hurricane Able, the strongest off-season Atlantic hurricane ever recorded, reached its peak strength of 115 miles per hour (185 km/h) off the coast of Cape Hatteras.

May 23

1917: Edward Lorenz, meteorologist and original founder of the field of chaos theory, was born in West Hartford, Connecticut.

May 24

1686: Daniel Gabriel Fahrenheit, inventor of the Fahrenheit temperature scale used primarily in the United States, was born in present-day Poland.

May 25

2004: A week of flooding and landslides on Hispaniola came to an end, leaving around 2,000 people dead.

May 26

1917: At one point thought to be the longest single tornado track on record, a family of several tornadoes killed over 100 people in Illinois and Indiana.

May 27

2018: For the second time in two years record flooding struck Ellicott City, Maryland.

May 28

1879: Milutin Milanković, famous for relating the cycle of ice ages to characteristics of Earth's orbit, was born in Erdut, Croatia (then Austria-Hungary).

Selected biography

Robert Case

Robert Case (December 16, 1939 – June 19, 2008) worked in various offices within the National Weather Service office for 38 years, developing a diverse background in various types of weather forecasting. He is best known for inspiring the naming of the 1991 Halloween Nor'easter as The Perfect Storm.

Recently selected biographies: Wladimir Köppen, John Park Finley, More...

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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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