Heatwave Updates: News and forecasts as scorching temperatures continue

Hearing about a predicted “heat dome” could trigger feelings of dread. But how does a heated dome actually work?

Here’s what you need to know about the weather phenomenon.

A heat dome is a high-pressure system at the very top of the atmosphere that helps create and envelop heat, much like a lid on a pot that traps steam.

Heat domes “on the order of 1,000 miles in diameter” can form under high-pressure weather systems, said Hosmay Lopez, an oceanographer and expert on extreme heat and climate change with the National Oceanic and Atmospheric Administration . They anchor themselves in place, accumulating heat, sometimes for weeks.

The term “heat wave” describes a weather-related increase in temperature, and the term “heat dome” refers to a high-pressure system that traps heat. The terms are often used interchangeably.

How are heat domes formed?

When a high pressure system enters an area, it pushes warm air toward the ground. Because flowing air acts as a cap, hot air cannot escape easily and it continues to heat up as it is compressed.

“You can actually repeat this process on a small scale,” said Greg Carbin, chief of forecast operations at the National Weather Service’s Weather Prediction Center. “When you inflate a flat tire, as air comes in and the pressure increases, the molecules move faster, they get closer together and they heat up.”

This high atmospheric pressure is linked to the configuration of jet streams, bands of fast winds which form high in the atmosphere in areas where cold air and warm air meet. Jet streams tend to be narrow, wavy corridors of air that move from west to east and migrate north to south. Sometimes jet streams can expand, become slower, even stagnant, and heavier.

Can heat domes happen anywhere?

Yes, it’s possible, but areas farther from water, with flatter topography, and located south of where jet streams migrate in summer are more prone to extreme heat domes. In the United States, this area corresponds to the central plains.

The thermal domes that have blanketed the Pacific Northwest in recent years still baffle meteorologists, Mr. Carbin said, because the region’s mountainous topography is the opposite of what is usually conducive to thermal domes. .

Thermal domes are associated with climate change. In the 1970s, there was one heat wave for every cold wave. As climate change accelerates, “that ratio is more than two to one, and in some areas it’s three to one,” says Dr. López.

A Queens metro commuter after an excessive heat warning was issued in July 2023.Credit…Maansi Srivastava/The New York Times

Are heated domes dangerous?

Yes. Heat stress is the most common cause of weather-related deaths, according to the World Health Organization. Since heat domes are associated with air stagnation, they can also lead to reduced air quality, drought, and increased fire risk. “These spots are very harmful to human health, especially for the elderly and people with cardiopulmonary diseases,” said Dr. López.

Find out how to stay safe during a heatwave here.

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