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Is ‘heat dome’ overhyped? Why some meteorologists dislike this term » Yale Climate Connections

Try as you may, you can’t escape heat domes – or at least you can’t escape running into this über-viral term, which has surged into U.S. weather and climate coverage over the past 10 to 20 years. It’s not that the phrase “heat wave” has gone away, but for a variety of reasons, “heat dome” has caught fire.

Much like “polar vortex,” a wintertime counterpart that gained traction in the 2010s, “heat dome” sneaked in through the back door. It doesn’t seem to have been used much by meteorologists or laypeople until it entered the vernacular sometime around the late aughts.

Read: What on Earth is a polar vortex? And what’s global warming got to do with it?

A 2011 New York Times feature noted the term’s newfound popularity, while also trying without much success to pin down its origin and speculating on alternatives: “For those who want a metaphor, ‘heat bubble’ might be more descriptive, some experts said – but then, the evocation of a bubble bath hardly carries the more ominous and attention-grabbing overtones of a ThunderDome or an Astrodome.”

While many folks now use “heat dome” as shorthand for a multiday heat wave, these terms aren’t really synonymous. A heat wave doesn’t require a dome-like atmospheric setup, and such a setup – a large, stagnant air mass – can actually occur even in the middle of winter.

Domes and not-quite-domes

The most basic depiction of a heat dome is of a roundish pile of air that’s being squashed to the surface by high pressure aloft, as cloud-free skies and full sun bake the ground underneath.

Is ‘heat dome’ overhyped? Why some meteorologists dislike this term » Yale Climate Connections
Figure 1. A rare example of a classic dome-like heat pattern from 3 p.m. CDT July 13, 1995, in the midst of a horrific multiday heat wave that caused more than 700 deaths in Chicago, Illinois. The black contours depict the height of the 500-millibar surface (roughly the midpoint of the mass of the atmosphere, about four miles high). Colors show temperature in degrees Fahrenheit. On this day, Chicago’s O’Hare International Airport had a low of 81°F and a high of 104°F. The images are drawn from a MERRA-2 reanalysis. (Image credit: Robertson713325 via Wikimedia Commons, CCO 1.0)

It’s true that heat waves involve upper highs, sinking air (subsidence), and lots of sunshine. But the subsidence can occur at different heights and different locations in different events, as opposed to forming a symmetric dome. The upper feature may be a ridge extending from the tropics rather than a classic closed upper high as shown in Fig. 1 above.

Sometimes the air at the heart of a heat wave isn’t being squashed so much as it’s just sitting there – perhaps for days on end, leading to stagnant conditions and poor air quality. Clouds may be sparse or absent all day if it’s a hot, dry air mass. If it’s moist, there could be a few fair-weather cumulus and even “popcorn convection,” showers or thunderstorms that pop up and down over the course of an hour or two, typically on the weak side.

John Monteverdi, professor emeritus at San Francisco State University and a longtime consulting meteorologist, is among those who aren’t enamored with the heat-dome concept. Monteverdi ran into the baying hounds of social media recently when he asserted on a broadcast meteorologist’s Facebook page that the Midwest/Northeast heat wave of June 2025 wasn’t really all that dome-like.

“I got what seemed like 5000 replies calling me a global-warming denier,” he said.

To illustrate his beef, Monteverdi pointed to a common midsummer setup in the Southwest U.S.: an upper-level ridge parked over the region, with scorching air and low pressure at the surface. Some U.S. heat waves are basically northward and eastward extensions of this semipermanent summer feature. At the core of the Southwest upper high, says Monteverdi, “there is very gentle rising motion. It’s barely moving aloft. That’s very different from saying there’s active subsidence that suppresses clouds. This is why the heat-dome [idea] is just terrible.”

Despite his distaste for the term, Monteverdi provided input to the American Meteorological Society (AMS) on its heat-dome entry in the AMS Glossary of Meteorology. The revised version is closer to the mark, he said, though he still disputes the emphasis on an upper high compressing the air below its center. Here’s the AMS definition as of this writing:

An exceptionally warm air mass at middle latitudes during the warm season that is associated with a synoptic-scale area of high pressure aloft. This area of high pressure aloft can have a doming effect on the warm air mass below by suppressing rising motion and the development of clouds and precipitation. In some cases, sinking air associated with the upper-level high pressure can produce further warming via compression. Warm surface air beneath a heat dome can persist for several days because the flow aloft is often calm and stagnant, especially when the upper-level high pressure can be characterized as a blocking high. The term “heat dome” has been popularized by the news media as a way to explain extreme heat and/or drought events across large regions.

Sometimes the most intense rising and sinking occurs around the periphery of the upper high or ridge, especially when an adjacent jet stream can give a dynamic boost to the vertical motion. These features can lead to pockets of strong subsidence that make an already-warm air mass even hotter on its fringes – quite different than the idea of a symmetric heat dome that’s most sizzling at its center.

A good example is the intense central and eastern U.S. heat wave of late June 2025. The most eye-popping records were set by incredibly sultry nights over the Midwest, some staying above 80°F, followed by blazing-hot days topping 100°F across large parts of the Northeast and New England as the hottest air pushed east. These areas were actually closer to a strong upper-level jet than they were to the center of the upper high (see Fig. 2 below).

Figure 2. Cloud streaks near the Appalachians show the prevailing west-northwest to east-southeast flow at 3 p.m. EDT on Tuesday, June 24, 2025. The trajectory of the descending low-level air was almost perpendicular to the mountain range, maximizing the warming effect. (Image credit: NOAA Satellites, with YCC annotations added)

Read: Unprecedented June heat along the Northeast urban corridor, brought to you by climate change

The titles alone of two papers from recent years underscore the message that heat waves can develop in more than one mode:

The flavors of heat waves in a changing climate

The most prolonged periods of unusual heat are typically caused by blocking highs. Such patterns can persist for days, and their starting and ending points are notoriously tough to predict. There’s been ongoing research on the concept of quasi-resonant amplification (QRA), by which “stuck” weather patterns, especially in summertime, appear to be favored as human-caused global warming proceeds. A recent paper led by Xueki Lee at the University of Pennsylvania and co-authored by Penn’s Michael Mann found that summertime QRA events have increased substantially over the past 70 years.

As one might expect, the intensity of heat waves is also boosted simply by the ever-rising baseline of a warmer atmosphere itself (see Fig. 3 below).

Figure 3. Illustration of how a modest rise in average temperature can more strongly boost the frequency of the most extreme heat events. (Image credit: Climate Central)

The most extreme heat waves can emerge from a black-swan blend of multiple factors. The one that slammed the U.S. Pacific Northwest and southwest Canada in June 2021, causing more than 900 confirmed deaths, was deemed by one research team “among the most extreme events ever recorded globally.”

Like many heat waves, this one was a mix of some features one might call dome-like and others that run counter to that popularized notion. Warm air from as far afield as the Philippine Sea moved toward North America, first gaining heat from condensation as it generated clouds and rainfall and then descending and warming further as it rounded an upper ridge over Washington and British Columbia. The ridge held in place for several days in blocking fashion, then migrated eastward. Rare easterly downslope winds led to further heating and compression along the west slopes of the Cascades, bringing unprecedented temperatures to Seattle, Portland, and other locations, including an all-time Canadian national high set and then broken twice, all over just three days, at the town of Lytton, British Columbia. The town was largely destroyed by fire on June 30 after topping out on June 29 with a stunning temperature of 49.6°C (121°F).

Erica Fleishman at the Oregon Climate Change Research Institute at Oregon State University led a review of more than 70 studies of the complex 2021 heat wave, published in June in the Bulletin of the American Meteorological Society. A rapid-response analysis by World Weather Attribution had found the extreme heat was “virtually impossible” without human-caused climate change. Other studies examined by Fleishman and colleagues found that the human-caused contribution to the unusually hot temperatures ranged from 5% to 20%. These findings aren’t necessarily in conflict: Even a small boost from climate change can push some events into unprecedented territory.

In their review, Fleishman and co-authors urged people to distinguish between causal factors, including heat domes in some cases, and the heat waves that result:

Not all heat waves are caused by heat domes, and not all heat domes cause heat waves. …In the Pacific Northwest, blocking patterns tend to be more frequent during winter than summer and typically are not associated with anomalously high heat during winter. Therefore, we refer to the event as a heat wave and encourage scientists, journalists, and other communicators to differentiate the manifestation of atmospheric phenomena (heat wave) from the meteorological mechanism that sometimes causes such phenomena (heat dome).

In an email, Fleishman added:

“Regardless of the terms, I’m just grateful when the profound effects on people’s lives and well-being worldwide are being covered.  That understanding of outcomes is essential for increasing efforts to mitigate human contributions to extreme heat and alleviate the consequences.”

Jeff Masters contributed to this post.

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Great Job Bob Henson & the Team @ Yale Climate Connections Source link for sharing this story.

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