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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  · Atmospheric Sciences)  · Tropical cyclones Featured article  · Disasters  · Water

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Did you know...

...that a fallstreak holes are cloud phenomena which are often mistaken for unidentified flying objects?

...that the Pakistan Remote Sensing Satellite is Pakistan's first remote sensing satellite?

...that HURDAT is a database of all known tropical cyclones in the northern Atlantic Ocean since 1851?

...that the 1995 Mayfest Storm was the costliest hailstorm in US history, and injured more than 100 people?

...that the Effects of Hurricane Hazel in Canada included flooding which killed 81 people?

...that the International Cloud Atlas was first published in 1896, yet is still in print?

Recent and ongoing weather

This week in weather history...

January 13

1979: A major snowstorm affected the Chicago area, dropping record snows of more than 16 inches (410 mm) in one day.

1982: Air Florida Flight 90 crashed into the Potomac River as a result of severe icing in a snowstorm, killing 78 people.

January 14

1888: The severe cold wave associated with the blizzard two days earlier reached its peak. The temperature reached −65 °F at Fort Keogh in Montana, the second lowest temperature ever recorded in the Contiguous United States.

2007: European windstorm Per struck parts of Scandinavia, killing six people.

January 15

1919: The Boston Molasses Disaster, caused in part by unusually warm temperatures, killed 21 people in Boston, Massachusetts.

January 16

1362: The Grote Mandrenke, Dutch for "Great Drowning of Men", produced an unprecedented storm tide in the Netherlands, killing 25,000 or more people.

January 17

1706: Benjamin Franklin, who would invent the lightning rod and introduce revolutionary concepts to meteorology, was born in Boston, Massachusetts.

1977: Snow was reported for the first time in West Palm Beach, Miami, and as far south as Homestead, Florida.

1982: An unprecedented outbreak of cold weather known as Cold Sunday brought record low temperatures to much of the Eastern United States.

January 18

1978: A subtropical storm formed in the central North Atlantic Ocean. It is the only known tropical or subtropical cyclone to form in the North Atlantic in the month of January.

January 19

1995: A helicopter crashed in the North Sea after being struck by lightning. Despite the high seas and stormy weather, all 18 passengers and crew were rescued.

2007: European windstorm Kyrill moved over the Baltic Sea towards northern Russia, after leaving a path of destruction from winds greater than 200 kilometers per hour (120 mph) across northern Europe. At least 44 people were killed.

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Mammatus cloud

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Rolling thunder cloud

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Cyclone Gafilo

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Mammatus cloud

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Dust Bowl

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  • Hurricane Isabel
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  • Category 5 Pacific hurricanes
  • 2003 Atlantic hurricane season
  • 1998 Pacific hurricane season
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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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