Portal:Weather
The Weather Portal
Weather is an all-encompassing term used to describe all of the many and varied phenomena that occur in the atmosphere of a planet at a given time. The term usually refers to the activity of these phenomena over short periods of hours or days, as opposed to the term climate, which refers to the average atmospheric conditions over longer periods of time. When used without qualification, "weather" is understood to be the weather of Earth.
Weather most often results from temperature differences from one place to another, caused by the Sun heating areas near the equator more than the poles, or by different areas of the Earth absorbing varying amounts of heat, due to differences in albedo, moisture, and cloud cover. Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure. The resulting pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation causes curvature of the flow via the Coriolis effect. These simple systems can interact, producing more complex systems, and thus other weather phenomena.
The strong temperature contrast between polar and tropical air gives rise to the jet stream. Most weather phenomena in the mid-latitudes are caused by instabilities of the jet stream flow (see baroclinity) or by weather fronts. Weather systems in the tropics are caused by different processes, such as monsoons or organized thunderstorm systems.
Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, while in December it is tilted away, causing yearly changes in the weather known as seasons. In the mid-latitudes, winter weather often includes snow and sleet, while in both the mid-latitudes and most of the tropics, tropical cyclones form in the summer and autumn. Almost all weather phenomena can occur year-round on different parts of the planet, including snow, rain, lightning, and, more rarely, hail and tornadoes.
Related portals: Earth sciences (Atmosphere · Atmospheric Sciences) · Tropical cyclones 
· Disasters · Water
Selected picture
Parallax is the phenomenon of the change in the apparent position of an object when viewed from different angles. It is demonstrated nicely in this foggy scene, where the reflection of the moon appears in a different position with respect to the street lamp when viewed in the reflection in the water.
Recently selected pictures: Global snow cover, Snow flakes, Sun dogs, More...
Selected article
The 2008 Super Tuesday tornado outbreak was a deadly tornado outbreak which affected the Southern United States and the lower Ohio Valley on February 5–6, 2008. In total, 87 tornadoes were confirmed in the outbreak's 15 hour span. Several destructive tornadoes struck heavily populated areas, most notably in the Memphis metropolitan area, in Jackson, Tennessee, and the northeastern end of the Nashville metropolitan area. Fifty-seven people were killed in the outbreak by tornadoes across four states and 18 counties, with hundreds injured and property damage totaling more than $500 million (USD).
The outbreak was the deadliest in the U.S. since the May 31, 1985 outbreak that killed 76 across Ohio and Pennsylvania (and also killed 12 in Ontario, Canada). It also was the deadliest tornado outbreak in both Tennessee and Kentucky since the 1974 Super Outbreak. In addition to the tornadoes, the same system produced significant straight-line wind damage, hail as large as softballs, or 4.50 inches (11 cm) in diameter, major flooding, significant freezing rain, and heavy snow across many areas of eastern North America.
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Did you know...
...that Hurricane Debbie is the only known tropical cyclone ever to strike Ireland?
...that the Tempest Prognosticator, one of the earliest attempts at a weather prediction device, employed live leeches in its operation?
...that eyewall replacement cycles are among the biggest challenges in forecasting tropical cyclone intensity?
...that the Braer Storm of January 1993 is the strongest extratropical cyclone ever recorded in the north Atlantic Ocean?
...that in medieval lore, Tempestarii are magicians with the power to control the weather?
...that the omega equation is essential to numerical weather prediction?
Recent and ongoing weather
- Wikinews weather portal
- February 8: European cold spell kills hundreds
- January 27: Report indicates Texas state parks still suffering following worst drought on record
- September 7: Drought conditions and high winds lead to wildfires in Texas
- August 29: Freshwater lakes in Texas show signs of extreme drought
- August 28: Tropical Storm Irene passes over New York
- 2012 Atlantic hurricane season
- 2012 Pacific typhoon season
- Tornadoes of 2012
This week in weather history...
February 23
1998: The worst tornado outbreak in Florida history killed 42 people in the northern half of the peninsula.
1999: An unexpected avalanche killed 31 people in the village of Galtür, Austria.
February 24
2007: Cyclone Gamede made its closest approach to Réunion island, where it dropped a staggering 5.5 meters (18 ft) of rain over a nine-day period.
February 25
1955: The Hunter Valley flood began with a major levee failure near Maitland, New South Wales.
February 26
2010: The third blizzard in less than a month struck the Northeastern United States with full force. The three storms, colloquially referred to as "Snowmageddon", resulted in more than 40 deaths, and a large area of the United States receiving more than 3 feet (0.91 m) of snow.
February 27
1938: The first of two consecutive powerful storms struck the area around Los Angeles, California, resulting in major flooding which would kill 115 people.
February 28
2003: Cyclone Graham made landfall at Eighty Mile Beach in Western Australia. One person drowned in the resulting flood. Portal:Weather/On this day list/February 29
Selected biography
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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Categories
Weather: Meteorology | Atmosphere | Basic meteorological concepts and phenomena | Climate | Clouds | Cyclones | Floods | Precipitation| Seasons | Severe weather and convection | Snow | Storms | Tornadoes | Tropical cyclones | Weather events | Weather lore | Weather hazards | Weather modification | Weather prediction | Weather warnings and advisories| Winds
Wikiprojects
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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