Ask the meteorologists: what is a cyclone? | Weather
Q: What is a cyclone?
A: A cyclone is a general term for a weather system in which the winds turn inward toward an area of low atmospheric pressure.
For major weather systems, the circulation pattern is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Types of cyclones include tropical cyclones, extratropical cyclones, and tornadoes.
A tropical cyclone is a rotating low-pressure weather system that has organized thunderstorms but no fronts. They form on the warm waters of the ocean.
Tropical cyclones with maximum sustained surface winds below 39 mph are called tropical depressions. Those with maximum sustained winds of 39 mph or more are called tropical storms. When a storm’s maximum sustained winds reach 74 mph, they are called hurricanes or typhoons. Hurricanes form over the Atlantic Ocean or the Caribbean Sea; typhoons form over the western Pacific Ocean.
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Extratropical cyclones are low pressure systems that form outside the tropics in response to chronic instability in westerly winds. Because this instability depends on large horizontal contrasts in temperature, concentrated regions of temperature change called fronts characterize extratropical cyclones.
These storms populate the mid and high latitudes, north of 35 degrees latitude in the Northern Hemisphere, and are therefore also referred to as “mid-latitude cyclones”. If the barometric pressure of a mid-latitude cyclone drops by at least 1 millibar per hour for 24 hours, the storm is called a “bomb cyclone”.
A tornado is a rapidly rotating column of air that extends downward from a thunderstorm to the ground. The most violent tornadoes are capable of enormous destruction with winds of up to 300 mph.
Tornadoes form in regions of the atmosphere that have abundant warm, moist air near the surface with drier air above, and a change in wind speed and direction with height above. above ground.
Photos: See the deadly destruction of tornadoes over the years
May 22, 2011: Joplin, Missouri
April 2011: Southeastern United States
February 5, 2008: “Super Tuesday” outbreak
April 2014: Southeast and Midwest
May 20, 2013: Moore, Oklahoma
March 18, 1925: Missouri, Illinois and Indiana
May 11, 1953: Waco, Texas
November 6, 2005: Evansville, Indiana
May 10, 2008: Southwestern Missouri
May 25, 2008: Iowa
February 29, 2012: Illinois
February 11, 2009: Oklahoma
April 28, 2011: Virginia
June 8, 1984: Barneveld, Wis.
May 1955: Udall, Kansas
March 2, 2012: Indiana
October 2013: Nebraska
May 4, 2003: Missouri
June 11, 2008: Iowa
July 8, 2014: Upstate New York
December 10-11, 2021: Kentucky, Tennessee, Ohio Valley, Southern United States
“Weather Guys” Steve Ackerman and Jonathan Martin are professors in the Department of Atmospheric and Oceanic Sciences at the University of Wisconsin-Madison.