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Portal:WeatherFrom Wikipedia, the free encyclopediaWeather 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 · Atmospheric Sciences) · Tropical cyclones  Ground fog is a type of fog formed by the ground cooling a warm layer of air near the surface to its dew point. This scene is in East Frisia, Germany just after sunrise. Recently selected pictures: Virga over London, Hurricane Isabel satellite, Hurricane Katrina Eye, More...  Recently selected articles: Hurricane Vince, Weather, More...  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... 
November 191421: St. Elizabeth's flood killed 2,000 or more people in the present-day Netherlands. November 211992: A three-day tornado outbreak began in the Southern United States, eventually producing six F4 tornadoes, two tornadoes with paths of more than 100 miles (161 km), and 26 deaths. 2006: The Late November 2006 Nor'easter gave parts of Georgia and South Carolina its earliest snowfall on record. November 221984: The Late November 1984 Nor'easter caused torrential rain and heavy surf in Florida. November 241703: An intense European windstorm began to affect southern England and the English Channel. This storm or series of storms would last for more than a week, killing as many as 15,000 at sea. 1982: Hurricane Iwa, one of only two significant tropical cyclones to directly affect Hawai'i, passed just northwest of Kauai. November 251950: Areas in and near the Appalachian Mountains are hit with heavy snow of up to 57 inches (145 cm).
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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 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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