Portal:Weather

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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Helkivad ööpilved Kuresoo kohal.jpg

A noctilucent cloud photographed from Soomaa National Park, Estonia. Noctilucent clouds are the highest clouds that form on Earth, being found in the mesosphere at altitudes of more than 70 kilometres (43 mi) above the ground. They are also among the rarest seen types of clouds: they are very dim (can only be seen after sunset illuminated by the sun below the horizon), and are typically only seen at latitudes between 50 and 70 degrees from the equator during the summertime.

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Cyclone Elita was an unusual tropical cyclone that made landfall on Madagascar three times. The fifth named storm of the 2003–04 South-West Indian Ocean cyclone season, Elita developed on January 24 in the Mozambique Channel. It strengthened to become a tropical cyclone before striking northwestern Madagascar on January 28. Elita weakened to tropical depression status while crossing the island, and after exiting into the southwest Indian Ocean it turned to the west and moved ashore for a second time on January 31 in eastern Madagascar. After crossing the island, the cyclone intensified again after reaching the Mozambique Channel, and Elita turned to the southeast to make its final landfall on February 3 along southwestern Madagascar. By February 5 it had undergone extratropical transition, and the remnants of Elita moved erratically before dissipating on February 13.

Elita dropped heavy rainfall of over 200 mm (8 inches), which damaged or destroyed thousands of houses in Madagascar. Over 50,000 people were left homeless, primarily in Mahajanga and Toliara provinces. Flooding from the storm damaged or destroyed more than 450 km² (170 sq mi) of agricultural land, including important crops for food. Across the island, the cyclone caused at least 33 deaths, with its impact further compounded by Cyclone Gafilo about two months later. Elsewhere, the cyclone brought rainfall and damage to Mozambique and Malawi, while its outer circulation produced rough seas and strong winds in Seychelles, Mauritius, and Réunion.


Elita's meandering track across Madagascar.

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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...

April 13

2014: After skirting the coast of Queensland for two days, Cyclone Ita began moving southeastward over the Coral Sea near Mackay. Ita caused A$1.1 billion in damage in Australia.

April 14

2017: Flash floods due to heavy rain killed more than 40 people in northwestern Iran, mostly in the East Azerbaijan Province.

April 15

1927: In New Orleans, 15 inches (380 mm) of rain fell in 18 hours, worsening an already historic flood and leading to the fateful (and ultimately unnecessary) decision to intentionally breach a levee south of the city.

April 16

2011: The final day of a three-day tornado outbreak brought dozens of tornadoes to the Mid-Atlantic and Southeastern United States, killing 26 people.

April 17

1979: Flooding along the Pearl River in Jackson, Mississippi crested at 43.28 feet (13.19 m), exceeding the previous record by more than 5 feet (1.5 m).

April 18

2014: An avalanche killed 16 Sherpa guides working on Mount Everest.

April 19

2000: Cyclone Rosita, one of the strongest tropical cyclones ever to strike the Kimberley region of Western Australia, reached Category 5 intensity (Australian scale), making landfall just after midnight near Broome.

Selected biography

Vilhelm Bjerknes

Vilhelm Friman Koren Bjerknes ForMemRS (/ˈvɪlhɛlm ˈbjɜːrknɪs/; 14 March 1862 – 9 April 1951) was a Norwegian physicist and meteorologist who did much to found the modern practice of weather forecasting. He formulated the primitive equations that are still in use in numerical weather prediction and climate modeling, and he developed the so-called Bergen School of Meteorology, which was successful in advancing weather prediction and meteorology in the early 20th century. (Full article...)

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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.

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