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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 .jpg) The eye of Hurricane Isabel as seen from the International Space Station. Recently selected pictures: Cirrus and cirrostratus clouds, Altocumulus undulatus, Lightning striking the Eiffel Tower, More...  Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve. Once an all human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition, forecast models are now used to determine future conditions. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. The use of ensembles and model consensus help narrow the error and pick the most likely outcome. There are a variety of end uses to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property. Forecasts based on temperature and precipitation are important to agriculture, and therefore to traders within commodity markets. Temperature forecasts are used by utility companies to estimate demand over coming days. On an everyday basis, people use weather forecasts to determine what to wear on a given day. Since outdoor activities are severely curtailed by heavy rain, snow and the wind chill, forecasts can be used to plan activities around these events, and to plan ahead and survive them. Recently selected articles: Climate of India, Subtropical cyclone, More...
...that the Four-State Tornado Swarm of 1787 was the first tornado outbreak on record? ...that Undulus asperatus is the first proposed new cloud type in more than 50 years? ...that Typhoon Meranti was the first of a record nine named storms in August during the 2004 Pacific typhoon season? ...that the doldrums are a colloquial term for the areas near the Intertropical Convergence Zone characterized by variable winds and heavy thunderstorms? ...that the 1848 Atlantic hurricane season featured five total tropical cyclones, including the Great Gale of 1848?  June 301792: The first tornado in Canadian history caused severe damage to forests on the Niagara Peninsula. 1912: One hundred twenty years later, the Regina Cyclone killed 28 people in Regina, Saskatchewan, making it the deadliest tornado in Canadian history. July 21997: The third tornado in 51 years struck Windsor, Ontario. July 41977: A severe windstorm, known as a derecho, struck areas of Wisconsin and Michigan. 1999: Another severe derecho produced 90 miles per hour (145 km/h) winds that downed 25 million trees in the Boundary Waters Canoe Area Wilderness of northeastern Minnesota. July 51805: Robert FitzRoy, captain of the [[HMS Beagle]] and a pioneering British meteorologist, was born in Suffolk, England. 1937: The hottest temperature in Canadian history, 45.0 °C (113.0 °F), was recorded at both Midale and Yellow Grass, Saskatchewan.
William Ferrel (1817 – 1891) was an American meteorologist who developed theories which explained the general mid-latitude atmospheric circulation in detail, now known as the Ferrel cell in his honor. Ferrel improved upon the concept of the Hadley cell by compensating for the Coriolis effect. Recently selected biographies: John Dalton, Sir George Stokes, More...
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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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