FENTON (AP) – With much of the midwest and the northeast of the United States (US) broiling – or about to broil – in extreme summer heat this week, meteorologists are talking about heatwaves and heat domes.
Both mean it’s really hot – and people will hear those terms a lot more as the world heats up. What’s the difference? Here’s what to know:
WHAT’S A HEAT DOME?
It’s helpful to think of a heat dome as what’s happening in the atmosphere. A heatwave is how that affects people on the ground, said atmospheric sciences research professor Ken Kunkel at North Carolina State University in the US.
When a high-pressure system develops in the upper atmosphere, it causes the air below it to sink and compress. That raises temperatures in the lower atmosphere.
Because hot air expands, it creates a bulging dome.
The boundaries of this week’s heat dome are not well-defined, Kunkel said, but the National Weather Service has said that the most extreme heat is expected in the Ohio Valley and the Northeast.
The eastern heat dome follows an earlier-than-usual one this month in the Southwest. Last year, there were 645 heat-related deaths in Phoenix.
WHAT IS A HEATWAVE?
A heatwave is defined by how intense the heat is, how long it lasts and where it occurs, said meteorologist Jeff Masters with Yale Climate Connections.
In general, several days of 30-plus degree temperatures in Texas are “no big deal”, Masters said. But farther north, it is forecasted to be in the mid- to high-30s over the Midwest and Northeast this week, with heat indexes of 38 degrees Celsius (oC) or greater.
“The population’s just not conditioned to that sort of heat,” he said.
The National Weather Service said that some areas likely will reach daily records, with the heatwave lasting all week and into the weekend in some places.
The combination of clear skies and the higher summertime angle of the sun can result in high heat index readings, a measure of temperature combined with humidity. Humidity makes the weather feel hotter because the body cools itself by sweating and has to work harder when the air’s already moist.
The Detroit area will be in the mid-30s, with a heat index around 38oC in some urban areas for the next few days. The normal high temperature for this time of year in Detroit is in the high 20s. Specifically, June 18 normal high is 27oC, meteorologist Brian Cromwell said.
Chicago broke a 1957 temperature record on June 17 with a high of 36.1oC. Hot and muggy conditions will continue this week, with peak heat indexes near 38oC, said the National Weather Service in Chicago.
In Cincinnati, Ohio, June 18 high were around 36oC, and it feel like 40oC, according to the weather service.
The high heat continued through the weekend. Albany, New York, temperatures were 35oC or hotter from June 18 through June 20, where it were peaked at 36oC, with heat indexes at 38oC or more, the weather service forecasted.
New York Governor Kathy Hochul said on June 18 that she has activated the National Guard to assist in any heat emergencies.
The US last year experienced the most heat waves since 1936, experts said. An Associated Press analysis of Centres for Disease Control and Prevention data found that the excessive heat contributed to more than 2,300 US deaths, the highest number in 45 years of records.
WHO’S UNDER THE HEAT DOME?
The heat dome will affect a broad swath of the eastern half of the country, from roughly the Great Plains states up through Maine.
Some locations could see their hottest temperatures on record for any month, Masters said.
A new study found that climate change is making giant heatwaves move more slowly and affect more people for a longer time, with higher temperatures over larger areas.
Almost 77 million people in the US were under extreme heat alerts on June 18.
Another excessive heat warning, caused by a heat dome, happened in the Phoenix area on June 20-21, when the highs reached 45.5oC and 47oC, respectively, said National Weather Service meteorologist Ted Whittock. June 18 forecasted high of 40.5oC, meanwhile, is normal for this time of year.
