BRUCE MacKINNON CARTOON: March 26, 2020
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The windows rattled in many Atlantic Canadian communities yesterday. Some of us experienced hurricane-force wind gusts as a powerful late fall storm tracked across the region.
At daybreak, while the mild south wind was being clocked at 105 km/h in Sydney N.S., Stacey sent me an email wondering why it was so very windy?
Where did all the wind come from?
Late fall and early spring storms can be very windy and that’s because, during these shoulder seasons, we are quite often transitioning from warm to cold, or cold to warm.
The gases that make up our atmosphere do interesting things as the temperatures change. When gases warm up, the atoms and molecules move faster, spread out, and rise – like steam off a pot of boiling water. When air is colder, the gases get slower and closer together. Colder air sinks.
Since gases behave differently at different temperatures, we end up with pockets with high pressure and pockets with low pressure. Now we’re getting to the part where wind happens. Gases move from high-pressure areas to low-pressure areas. The bigger the difference between the pressures, the faster the air will move from the high to the low pressure. That rush of air is the wind we experience.
After sunrise yesterday morning, the air temperature in Labrador City was –12 C; it was +8 C in Stephenville and Corner Brook, N.L.; that’s a 20-degree temperature difference. As the crow flies, that’s less than 750 km – a huge temperature spread and, consequently, air pressure difference over that distance.
It’s not nearly as windy today, but there’s still lots of wind on the way. A cold northwest wind will give us significant wind chill on Thursday. A weekend warm-up will follow with a strong south wind for the weekend. By Monday, the wind will be out of the northwest with gusts to 70 km/h.
’Tis the season!
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Cindy Day is the chief meteorologist for SaltWire Network.