Wednesday, August 31, 2016

Goodbye to meteorological summer

National Hurricane Center forecast map for soon-to-be tropical storm Hermine. The storm is forecast to impact Florida over the next 48 hours before heading up the east coast. (National Hurricane Center)

Today is the last day of the summer season as far as meteorologists are concerned. Thankfully, Mother Nature lingers a little behind, so we can still expect more summer weather here in Montreal, usually well into September. But the signs of autumn are there: the kids are back to school, leaves turning slightly, and longer, cooler nights producing heavy morning dew.

Looking back briefly at June through August, temperatures averaged above-normal values. Some locations in southern Quebec and New England are expected to show their warmest August on record. Until the middle of August, it was also a very dry summer in Montreal. That has changed in the last two weeks, with more rain falling this month than in the previous two combined. Overnight, Montreal added to the monthly total as scattered thunderstorms developed. More are possible later Wednesday, before we say goodbye to August. At this time, the long holiday weekend looks spectacular here in southern Quebec, sunny and seasonable, with high temperatures in the middle 20s.

Across North America, the weather has been extremely active of late. A powerful and rare summer low pressure area pounded Newfoundland Monday and Tuesday, with torrential rain and winds in excess of 130km/h. A wind gust to 121km/h in Twillingate was the strongest August wind on record for that community. The previous record was 107km/h, set in 2007. Strong thunderstorms this week have produced severe flash flooding in Ohio and parts of Colorado. Deep hail fell in Colorado Springs on Monday, requiring snow plows to clear the streets.

Satellite image of tropical depression 9, Wednesday morning over the Gulf of Mexico. This system is forecast to strengthen into tropical storm Hermine later today. (NOAA)
The Tropics
In the tropics, tropical depression 9 is still meandering in the Gulf of Mexico, 640km south of the Florida coast. This system is expected to strengthen into a tropical storm later Wednesday, and be named Hermine. Warnings are in effect for a portion of the big bend area of Florida, as well and the Atlantic coast northward into Georgia. Heavy rain, up to 300mm (12 inches), and 60mph winds are forecast over the next 24 to 36 hours. The storm is then expected to move back over Atlantic waters over Labor Day weekend. All interests up and down the east coast of the US into Atlantic Canada will need to pay close attention to the future path of this tropical storm. Further out in the open waters of the Atlantic, hurricane Gaston has become a major storm, with 115mph winds. Gaston is no threat to land at this time. Meanwhile in the Pacific Ocean, hurricanes Madeline and Lester are expected to pass dangerously close to Hawaii over the next 48 hours. Warnings are in place for Madeline, forecast to move just south of the Big Island early Thursday morning.

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