Summer is the time for blue skies, gentle breezes, and puffy clouds that look like harmless marshmallow fluff. Psych! Summer is the time for stormy weather. “Unstable conditions can exist in the atmosphere at any time of year, but the level and depth of instability is greatest in the summer,” says Geoff Coulson, a meteorologist with Environment and Climate Change Canada. He prepped us on the big three of the season.
Tornadoes
Tornadoes form in different ways, “and the experts still aren’t quite sure exactly how,” says Coulson. But they likely come from some combination of powerful updrafts and downdrafts, and wind shear—the change in speed or direction of wind. In one scenario, wind shear generates a cylinder of air, like a cardboard paper towel tube, rolling horizontally near the ground. “If that tube of air encounters a strong updraft, the tube can be brought into the vertical,” says Coulson. And sometimes, that tube can “stretch and narrow, causing the winds to spin more violently.” Okay. But how does a Sharknado form?
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Lightning and thunder
When static electricity builds between thunderclouds, or between the clouds and the ground, lightning is the result. And it’s hot. The heat causes the air to noisily expand. Hello, thunder. But you can see lightning without hearing thunder. “It’s often called ‘heat lightning,’ ” says Coulson. “It’s far enough away that the sound wave dies out before it reaches you.”
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Hail
Even on a hot summer day, the temperature up in a thunderstorm cloud is very cold: -35°C to -50°C. As warm, moist air rises, it condenses and forms particles. Once those particles become too heavy, they fall. Big hail is more common in the summer because that season’s strong updrafts penetrate higher into the cold atmosphere and keep the particles “bouncing around” longer inside the storm clouds, where they have more opportunity to grow, says Coulson. This produces hailstones that are “loonie-, toonie-, golf ball–, or even baseball-sized.” Ouch.
Awe-inspiring photos of summer storms
This article was originally published in the Summer 2020 issue of Cottage Life.
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