A Record Heatwave in the Southwest Grounds Planes

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The first week of summer is getting off to an especially hot start in the American Southwest. According to ABC News, temperatures reached 118°F on Monday, June 19, tying the regional record for that day set last year. Today, Tuesday, June 20, the mercury is expected to climb even higher, and airlines in Phoenix are canceling flights as a precaution.

American Airlines grounded close to 50 flights scheduled to take off from Sky Harbor International Airport in Phoenix Tuesday morning, The Arizona Republic reports. With the National Weather Service predicting highs of 119°F, the Bombardier CRJ aircraft used by the airline for regional flights has been deemed unfit to travel.

The maximum operating temperature of the Bombardier CRJ aircraft is 118°F—at that point, experts worry that the air is no longer dense enough for the plane to take off and fly efficiently. Extreme heat isn’t a common problem for airlines, with temperatures approaching the 120s in the Southwest less than one day a year on average. But this summer is already shaping up to be one for the record books. Above-average heat is projected to scorch the region from now through September. The forecast fits into a recent trend of intense Southwestern summers which scientists believe are connected to climate change.

While many local flyers will be inconvenienced by the heat today, travelers flying beyond Arizona can expect a smooth trip. Larger jets, like Boeing and Airbus, have maximum operating temperatures of 126°F and 127°F, respectively—higher than any temperature that's been recorded in Phoenix to date.

[h/t ABC News]

Britain Is in the Midst of a Rare ‘Wind Drought’

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Generating renewable energy in Britain is a little less than a breeze these days: A “wind drought” is halting the country’s wind turbines.

This month’s wind energy output is down 40 percent from the same time last year, New Scientist reports. On average, about 15 percent of Britain’s electricity comes from wind power. Data starting from July 1 of this year put the monthly average closer to 6.9 percent. Last month, turbines were producing less than 2 percent of Britain’s electricity—the lowest output in two years.

That’s with even more wind turbines being installed over the course of the past year, New Scientist says. The data aren’t entirely surprising, though. The jet stream tends to make the UK’s weather drier and calmer during the summer and wetter and stormier during the winter. But the high pressure the jet stream has brought with it this year has been unusually prolonged, scientists say.

“It’s like a lid, it keeps everything still,” UK Met Office spokesperson Grahame Madge told New Scientist. “From the forecast looking out over the next couple of weeks, there doesn’t seem to be any significant change on the way.”

The wind drought shouldn’t cause too many problems in the short term. Electricity demand is low during the summer (very few British homes have air conditioning), and the country’s been able to compensate for the lack of wind by burning more natural gas. If the wind drought continues to persist, though, UK residents may begin to see an increase in utility fees. Natural gas prices have already risen with the increased demand.

“As we continue to transition to a low-carbon energy system, managing the intermittency of renewable power an important role in balancing supply and demand,” a National Grid spokesperson told New Scientist. “However, we have planned for these changes and [are] ready to play our part.”

The wind drought comes about eight years after British politicians vowed to reduce the UK's dependence on fossil fuels. Last year was the first year that electricity generated from low-carbon energy sources like solar power, wind power, and nuclear power outpaced high-carbon energy sources like coal and natural gas. This summer’s wind drought may make it difficult to improve on last year’s numbers.

[h/t New Scientist]

Why Does the Sky Look Green Before a Tornado?

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A common bit of folklore from tornado-prone parts of the U.S. says that when the skies start taking on an emerald hue, it's time to run inside. But why do tornadoes tend to spawn green skies in the first place? As SciShow's Michael Aranda explains, the answer has to do with the way water droplets reflect the colors of the light spectrum.

During the day, the sky is usually blue because the shorter, bluer end of the light spectrum bounces off air molecules better than than redder, longer-wavelength light. Conditions change during the sunset (and sunrise), when sunlight has to travel through more air, and when storms are forming, which means there are more water droplets around.

Tornadoes forming later in the day, around sunset, do a great job of reflecting the green part of the light spectrum that's usually hidden in a sunset because of the water droplets in the clouds, which bounce green light into our eyes. But that doesn't necessarily mean a twister is coming—it could just mean a lot of rain is in the forecast. Either way, heading inside is probably a good idea.

For the full details on how water and light conspire to turn the sky green before a storm, check out the SciShow video below.

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