Science Behind the Forecast: What is a ‘heat dome’?

LOUISVILLE, Ky. (WAVE) - A heat dome occurs when the atmosphere acts like a lid, trapping heat near the planet’s surface, many times leading to heat waves. It can last from days to weeks.

Research has found that when high-pressure combines with La Nina’s (the cooling of the ocean surface in the central and eastern tropical Pacific Ocean) influence, large areas of heat become trapped beneath high-pressure’s dome. As the eastern and central Pacific Ocean cools down, the western Pacific heats up, creating a strong temperature gradient. Scientists found that this gradient was a significant trigger for heat domes.

Heat domes are usually associated with the jet stream (relatively narrow bands of strong wind in the upper levels of the atmosphere that typically runs west to east). The jet stream meanders back and forth to the north and south. Sometimes the “waves” in the jetstream become larger, move slower and in some cases, become stationary.

When the jetstream moves further north, air piles up and sinks, warming as it does so. Sinking air keeps skies clear, allowing the sun to heat up things.

When the weather pattern becomes stagnant in a heat dome, there’s usually light wind and increased humidity. These factors make it harder for our bodies to cool off.

Excessive heat is the top weather-related killer in the United States. In 2021, 190 people were killed by the heat in the U.S. Flooding was the second leading killer; 146 people died.

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