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Weather

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File:HurricaneAndrewSequence md.jpg
Composite satellite image showing the progress of a hurricane weather system approaching the east coast of America

Weather comprises all the various phenomena that occur in the atmosphere of a planet. On Earth the regular events include wind, storms, rain, and snow, which occur in the troposphere or the lower part of the atmosphere. Weather is driven by energy from the sun, with key factors being temperature, humidity, atmospheric pressure, cloud cover, wind speed, and elevation.

Weather prediction

Weather stations all around the world measure these conditions on a continuous basis. The weather system is an inherently chaotic system. Practically this means that meteorologists can only predict the weather a few days in the future. In fact it was through studying weather systems that chaos theory first emerged, pioneered with the aid of early computers by Edward Lorenz. Recently, though, it has been shown that the theoretical time ahead that it is possible to forecast is not as short as previously thought. Research suggests that problems with the formulas used in current models remains a limiting factor in the accuracy of predictions, rather than the inherently chaotic nature of the weather. This still only extends the forecast time by at most a week. However, scientists are continuously working to extend the length of the forecast period. In the last decade, advances in the science now allow forecasters to give a general idea of future conditions, such as whether the temperature or precipitation will average above or below normal well into the future. These types of forecasts have become increasingly more accurate.

Weather prediction is an area of much active research, due to the advantages that an accurate forecast of the weather would bring. Chaos theory says that small changes in the initial conditions increase exponentially over time, until the weather is very different from what it would have been under slightly different circumstances. Forecasters are able to increase the quality of their predictions by calculating a number of different scenarios making small changes to the initial conditions of each. These end results are then compared, and the most common scenario is chosen as the forecast. This also has the advantage that forecasters have an estimate of the reliability of their forecast - if different models produce wildly incompatible results the forecast is known to be unreliable.

List of named weather, climatic or atmospheric patterns

See also: Meteorology, climate, Cycles, severe weather, extreme weather, Groundhog Day, wind, TV Nova, Weather forecasting, AccuWeather, Weather lore, Convective Available Potential Energy

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