The weather portal

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. On Earth, most weather phenomena occur in the lowest level of the planet's 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 middle latitudes, such as extratropical cyclones, are caused by instabilities of the jet streamflow. Because Earth's axis is tilted relative to its orbital plane (called the ecliptic), 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 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. 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, the 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. (Full article...)

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Lightning over Oradea Romania 2.jpg

Lightning strikes in the outskirts of Oradea, Romania, during a thunderstorm on August 17, 2005. This storm system went on to cause major flash floods over Southern Romania.

Recently selected pictures: Snow-swept trees, Low pressure

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Snow events are a rarity in the U.S. state of Florida, as freezing temperatures in the state are generally caused by the cold and dry winds of anticyclones. Most of the state is in a rare portion of the continental United States which receives a mean maximum monthly snowfall amount of zero, the only other such areas being southern Texas and California. However, snow does occur, especially in the northern interior sections of the state, sometimes more than once in a season. Areas near Jacksonville have seen several inches of snow on occasion, and snow flurries have been reported as far south as Homestead. Generally, for snow to occur, the polar jet stream must move southward through Texas and into the Gulf of Mexico, with a stalled cold front across the southern portion of the state curving northeastward to combine freezing air into the frontal clouds.

Snowfall events by month in Florida

Recently selected articles: Great Lakes Storm, Extratropical cyclone, More...

Did you know...

...that a hurricane force wind warning is issued by the United States National Weather Service for storms that are not tropical cyclones but are expected to produce hurricane-force winds (65 knots (75 mph; 120 km/h) or higher)?

...that the Automated Tropical Cyclone Forecasting System is a software package for tropical cyclone forecasting developed in 1988 that is still used today by meteorologists in various branches of the US Government?

...that a cryoseism is a sudden ground or glacier movement that can occur due to water freezing or ice cracking after drastic temperature changes?

...that BUFR is a binary data format standardized by the World Meteorological Organization for storing observation data from weather stations and weather satellites?

...that the Northwest Weather and Avalanche Center issues weather forecasts for conditions that can cause avalanches in the mountains of western Washington and northwestern Oregon?

...that a wind chill warning is issued by the National Weather Service when a combination of wind and cold temperatures is expected to cause life-threatening conditions for anyone caught outside?

Recent and ongoing weather

This week in weather history...

January 23

1971: The temperature dropped to −80 °F (−62 °C) in Prospect Creek, Alaska, the coldest temperature ever recorded in the United States.

January 24

2009: European windstorm Klaus made landfall near Bordeaux, France, with wind gusts of up to 200 kilometres per hour (120 mph).

January 25

1990: A European windstorm known as the Burns' Day Storm killed almost 100 people, mainly in the United Kingdom.

January 26

1967: A major blizzard dumped 23 inches (58 cm) of snow in Chicago, a record amount for a single storm.

January 27

2008: Cyclone Gene made landfall on Fiji, killing 8 people.

January 28

2004: Cyclone Elita made its first of three landfalls on Madagascar.

January 29

1989: Cyclone Firinga dropped torrential rain on the French overseas department of Réunion, including 1,309 millimetres (51.5 in) at Pas de Bellecombe in just 24 hours.

Selected biography

Portrait of Clement Lindley Wragge

Clement Lindley Wragge (18 September 1852 – 10 December 1922) was a meteorologist born in Stourbridge, Worcestershire, England, but moved to Oakamoor, Staffordshire as a child. He set up the Wragge Museum in Stafford following a trip around the world. He was a Fellow of the Royal Geographical Society and in 1879 was elected Fellow of the Royal Meteorological Society in London. To the end of his life, he was interested in Theosophy and spiritualism. During his tour of India he met with Mirza Ghulam Ahmad of Qadian, the founder of the Ahmadiyya movement in Islam who had claimed to be the Mahdi, the messianic redeemer awaited by Muslims. Sir Arthur Conan Doyle sought him out in New Zealand to ask for his views on spiritualism before writing The Wanderings of a Spiritualist in 1921. After training in law, Wragge became a meteorologist, his accomplishments in the field including winning the Scottish Meteorological Society's Gold Medal and years later starting the trend of using people's names for cyclones. He travelled widely, giving lectures in London and India, and in his later years was an authority on Australia, India and the Pacific Islands. (Full article...)

Previously selected biographies: Robert Case, Wladimir Köppen, More...

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Uses material from the Wikipedia article Portal:Weather, released under the CC BY-SA 3.0 license.