What is a heat dome? A meteorologist explains the weather phenomenon baking large parts of the US

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What is a heat dome? A meteorologist explains the weather phenomenon baking large parts of the US

NWS HeatRisk' fifu-data-src="https://s.yimg.com/ny/api/res/1.2/cVLlRQrXwI2KkELh3jxyfw--/YXBwaWQ9aGlnaGxhbmRlcjt3PTk2MDtoPTUxMA--/https://media.zenfs.com/en/the_conversation_us_articles_815/bf310e40398d4a38e0c3b3627d00976d" data-src="https://s.yimg.com/ny/api/res/1.2/cVLlRQrXwI2KkELh3jxyfw--/YXBwaWQ9aGlnaGxhbmRlcjt3PTk2MDtoPTUxMA--/https://media.zenfs.com/en/the_conversation_us_articles_815/bf310e40398d4a38e0c3b3627d00976d">Heat domes sent temperatures soaring in early August 2024. Orange is moderate heat risk for Aug. 2, red is major, and purple is extreme.

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Heat domes, which have

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across the U.S., occur when a persistent region of high pressure traps heat over an area. A heat dome can linger for days to weeks, leaving the people, crops and animals below to suffer through stagnant, hot air that can feel like an oven.

Typically, heat domes are tied to the behavior of

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, a band of fast winds high in the atmosphere that generally runs west to east.

Normally, the jet stream has a

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north and then south and then north again. When these meanders in the jet stream become *******, they move slower and can become stationary. That’s when heat domes can occur.

data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==Heat domes involve high-pressure areas that trap and heat up the air below.

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When the jet stream swings far to the north, air piles up and sinks. The

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, and the sinking air also keeps skies clear since it lowers humidity. That allows the sun to create hotter and hotter conditions near the ground.

If the air near the ground passes over mountains and descends, it can

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. This downslope warming played a large role in the extremely hot temperatures in the Pacific Northwest during a

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, when Washington set a state record with 120 degrees Fahrenheit (49 Celsius), and temperatures reached 121 F in British Columbia in Canada, surpassing the previous ********* record by 8 degrees F (4 C).

The human impact

Heat domes normally persist for several days in any one location, but they can last longer. They can also move, influencing neighboring areas over a week or two. The heat dome that started in Texas and Mexico in

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spread into the Southwest in July.

On rare occasions, the heat dome can be more persistent. That happened in the

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, when as many as 10,000 people ***** during weeks of high summer heat. It also happened over much of the ******* States

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of the 1930s.

A heat dome can have serious impacts on people, because the stagnant weather pattern that allows it to exist usually results in weak winds and an increase in humidity. Both factors make the heat feel worse –

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– because the human body is not cooled as much by sweating.

The

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, a combination of heat and humidity, is often used to convey this danger by indicating what the temperature will feel like to most people. The high humidity also reduces the amount of cooling at night. Warm nights can leave people without air conditioners unable to cool off, which increases the risk of heat illnesses and deaths. With global warming,

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, too.

One of the worst recent examples of the impacts from a heat dome with high temperatures and humidity in the U.S. occurred

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, when an estimated

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over five days.

This article, originally published June 22, 2022, has been updated.

This article is republished from

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, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by:

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,

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Read more:

William Gallus receives funding from the National Science Foundation.

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#heat #dome #meteorologist #explains #weather #phenomenon #baking #large #parts

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