If you’re sweating through the summer of 2023—we can’t help you. But we can help you understand why some areas are really hot, while others are cool and wet this year
Lesson summary
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Coming up today: Are you trapped under a heat dome? Millions of people are, from Asia to North America to Europe. On today’s lesson, you’ll learn about why the heat waves in the northern hemisphere seem so intense this year. There’s lots of new vocabulary in this one, so I know you’ll learn a lot.
In the second half of this audio lesson, I’ll show you how to use the English phrasal verb “cool off.” And we have a quote of the week. Let’s get started.
Sweltering ‘heat domes’ are the result of a jet stream pattern
If there’s one word that describes summer 2023 so far , it’s heat.
Europe, the U.S., and Asia have all suffered from extreme heat for extended periods. Globally, June 2023 was the hottest month on record. Cities as varied as Tokyo in Japan, Rome in Italy, and Phoenix in the U.S., have all experienced temperature-related records.
Scientists believe this is caused by a specific jet stream pattern. The jet stream is a band of fast-moving air in the atmosphere, several kilometers above the earth’s surface. The jet stream is what drives much of the northern hemisphere’s weather patterns. One meteorologist describes the jet stream as a conveyor belt, delivering storms and weather around the world.
But the jet stream is variable: it’s not always in the same spot. It shifts and bends and changes shape, it goes up and down. That is partly why the weather in the northern hemisphere tends to be so varied.
This June, the jet stream formed what scientists call a “wavenumber 5” pattern. That means it formed five large, U-shaped curves in its loop around the globe. And those curves haven’t been moving much.
Picture the jet stream moving like a sine wave, forming five peaks and five valleys as it circles the globe. Now picture the area under the peak of this wave. That area is called a “heat dome.”
Here’s what happens. The area under the arc, the heat dome, is a high-pressure area. The high atmospheric pressure traps heat and keeps clouds out. In normal weather patterns, high pressure systems produce clear skies and warm, sunny weather. Then, the weather shifts and it cools off again.
But when the jet stream is fixed in its waveform 5 position, the high-pressure system sits over an area for a long time. And strange things start to happen. Warm air rises from the ground, but gets pushed back down again by the high pressure.
The high atmospheric pressure compresses that air as it pushes it down. That squeezes more heat into a smaller area, causing the temperature to go up. So this becomes like a self-reinforcing system: warm air rises; the high pressure compresses warm air into a smaller space; the air gets even hotter; the air moves up again because it’s hot; and the cycle repeats.
And because the jet stream is not moving, the areas under this “heat dome” don’t get any relief: it just gets hotter and hotter. Even worse, the heat dries out the ground, making the area susceptible to wildfires—which can push temperatures even higher.
But what about clouds and rain? In a normal weather pattern, the high pressure system would move on, a low pressure system would take over, clouds would enter the area, it would rain, and it would cool off . But the jet stream is not moving, and the high atmospheric pressure stays over the same area and keeps clouds out.
If the clouds are kept out of the heat dome, where do they go? They go everywhere else. So many areas outside a heat dome get a lot of rain, even as areas under the heat dome are suffering from stifling heat and drought.
For example, in the U.S., Texas, Oklahoma, Nevada, Arizona, and Colorado have experienced record-setting heat. Those areas are under the heat dome. JR reports that in Chicago, he’s only had to use the air conditioning a few times this year—Chicago is outside the heat dome. But Chicago got heavy, heavy rains in early July—in some areas, six to eight inches of rain fell in just 24 hours. All the rain that was meant for the heat dome poured down on Chicago and other areas outside the heat dome instead. It’s the same in Asia. It’s hot in Xianjing, China, but pouring rain in Beijing.
How can this weather pattern end? The jet stream could keep its same form, but shift position. That would put different areas under the heat dome. But the heat domes won’t go away until the jet stream breaks its wave-shaped pattern.
Why is the jet stream doing this? It’s not fully clear. Higher ocean temperatures make heat domes worse, and ocean temperatures have been rising. The jet stream is powered by the temperature difference between the Arctic air and the warmer air below it. The Arctic is warming faster than any other part of the globe. That means that the difference in temperature between the Arctic and more moderate climates—that difference is narrowing. But it’s not yet clear if this causes the jet stream to form its waveform pattern.
Normally, Europeans flock to the beach—they go south for the summer. This year, they might want to go north. Oslo sounds good right about now!
Spain, France, Italy—all vacation destinations on the Mediterranean and they are—at least at the end of July—they were suffering from a really intense heat wave.
If you have a vacation in the U.S. or Europe or China or anywhere with a heat dome—don’t overdo it. Plan a few hours mid-day to just relax inside. Do your activities early in the morning or in the evening. Heat like this is no joke.
Or come visit me in Mexico City—no heat dome here, at 2,200 meters above sea level.
Quote of the Week
It’s Monday, so I’ve got a quote of the week for you. Here it is: “Well-timed silence hath more eloquence than speech.” This is from Martin Tupper, an English poet and novelist.
“Hath” is Old English and it simply means “has.” So it goes like this: “Well-timed silence has more eloquence than speech.” I like this because if you listen to a good speaker, you’ll notice they put silence in key moments. If you’re listening to a speech and you hear silence…what do you do? You pay attention. You pay close attention to what comes next.
So here again is the quote from Martin Tupper: “Well-timed silence hath more eloquence than speech.”
Great stories make learning English fun
