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 layer of the planet's atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature, precipitation, and other atmospheric conditions, 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 104 °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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Average annual temperatures across India: Lavender is Below 20.0 °C (< 68.0 °F), blue is 20.0–22.5 °C (68.0–72.5 °F), green is 22.5–25.0 °C (72.5–77.0 °F), yellow is 25.0–27.5 °C (77.0–81.5 °F), and red is Above 27.5 °C (> 81.5 °F)
Average annual temperatures across India: Lavender is Below 20.0 °C (< 68.0 °F), blue is 20.0–22.5 °C (68.0–72.5 °F), green is 22.5–25.0 °C (72.5–77.0 °F), yellow is 25.0–27.5 °C (77.0–81.5 °F), and red is Above 27.5 °C (> 81.5 °F)

The climate of India is composed of a wide range of weather conditions across a large geographic scale and varied topography. Analyzed according to the Köppen system, India hosts six major climatic subtypes, ranging from desert in the west, to alpine tundra and glaciers in the north, to humid tropical regions supporting rainforests in the southwest and the island territories. Many regions have starkly different microclimates. The nation has four seasons: winter (January and February), summer (March to May), a monsoon season (June to September), and a post-monsoon period (October to December).

India's unique geography and geology strongly influence its climate; this is particularly true of the Himalayas in the north and the Thar Desert in the northwest. The Himalayas act as a barrier to the frigid katabatic winds flowing down from Central Asia. Thus, North India is kept warm or only mildly cold during winter; in summer, the same phenomenon makes India relatively hot. Although the Tropic of Cancer—the boundary between the tropics and subtropics—passes through the middle of India, the whole country is considered to be tropical.

As in much of the tropics, monsoonal and other weather conditions in India are unstable: major droughts, floods, cyclones and other natural disasters are sporadic, killing or displacing millions. India's long-term climatic stability is further threatened by global warming. Climatic diversity in India makes the analysis of these issues complex.

Recently selected articles: Subtropical cyclone, Precipitation, More...

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Cyclone Catarina, the only major tropical cyclone ever observed in the Southern Atlantic Ocean, as it appeared from the International Space Station on March 26, 2004.

Recently selected pictures: Roll cloud, Hoar frost, Snowflakes, More...

More did you know...

...that the Flying river is the name given to the transport of water vapor from the Amazon rainforest to southern Brazil?

...that hurricane shutters are required for all homes in Florida unless impact-resistant glass is used?

...that the Joint Institute for Marine and Atmospheric Research is a combined weather and ocean research institute with the cooperation of the Office of Oceanic and Atmospheric Research and the University of Hawaiʻi?

...that the SS Central America was sunk by a hurricane while carrying more than 30,000 pounds (13,600 kg) of gold, contributing to the Panic of 1857?

...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?

Recent and ongoing weather

This week in weather history...

May 18

1986: Cyclone Namu, the worst tropical cyclone ever to affect the Solomon Islands, killed 150 people as it passed through the island nation.

May 19

2018: Cyclone Sagar struck northwestern Somalia, killing 56 people in three countries. It was the strongest tropical cyclone on record to strike Somalia.

May 20

2010: Cyclone Laila made landfall in Andhra Pradesh, India, killing 65 people.

May 21

1953: A deadly tornado killed 2 people in Port Huron, Michigan, and crossed the St. Clair River into Canada where it killed 4 more people in Sarnia, Ontario.

May 22

1981: The GOES 5 weather satellite was launched. Part of the Geostationary Operational Environmental Satellite program, GOES 5 would provide weather forecasting data to the United States until its main imaging instrument failed in 1984.

May 23

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

May 24

2001: A tropical cyclone reached peak intensity in the northern Indian Ocean with a central pressure of 932 millibars (27.52 inHg). At the time it was the strongest tropical cyclone on record in that region, and would eventually kill hundreds upon landfall in the Saurashtra region of India.

Selected biography

Wladimir Peter Köppen

Wladimir Petrovich Köppen (/ˈkɜːpən/ KUR-pən; German: [ˈkœpn̩]; Russian: Влади́мир Петро́вич Кёппен, romanizedVladímir Petróvich Kyoppen, IPA: [vlɐˈdʲimʲɪr pʲɪˈtrovʲɪtɕ ˈkʲɵp(ː)ʲɪn]; 25 September 1846 – 22 June 1940) was a Russian–German geographer, meteorologist, climatologist and botanist. 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 made significant contributions to several branches of science, and coined the name aerology for the science of measuring the upper air/atmosphere. (Full article...)

Previously selected biographies: John Park Finley, Edward Norton Lorenz, More...

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The scope of WikiProject Weather is to have a single location for all weather-related articles on Wikipedia.

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 Wikipedia's coverage of tropical cyclones.

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

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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