Waterspouts, lake-effect showers likely in Ontario as Great Lakes run a fever

·2 min read
Waterspouts, lake-effect showers likely in Ontario as Great Lakes run a fever
Waterspouts, lake-effect showers likely in Ontario as Great Lakes run a fever

The Great Lakes are running warm for this time of year. Water temperatures on all five lakes are the warmest we’ve seen in mid-October since 1995, and Lake Superior has run above-normal all year. Warm lake waters will play a large role in upcoming fall weather, and we’ll get a taste of that influence in southern Ontario to close out the weekend.

Great Lakes Water Temperatures October 16 2021
Great Lakes Water Temperatures October 16 2021

The lakes will retain much of their heat even as air temperatures cool off in the coming days and weeks. An approaching cold air mass above the surface will set up a large temperature contrast over the bodies of water, creating an unstable environment overhead.

Lake-Effect Precip Formation
Lake-Effect Precip Formation

COLD AIR OVER WARM LAKES LEADS TO LAKE-EFFECT SHOWERS

Adding on the northeasterly wind direction off of Lake Huron and Georgian Bay, all ingredients are present for lake-effect showers throughout Sunday.

Lake Effect Rain Totals
Lake Effect Rain Totals

These narrow bands of heavy rain could tick up rainfall accumulations upwards of 10-20 mm locally, whereas other areas across southern Ontario may only see trace amounts.

WATERSPOUTS ARE ALSO POSSIBLE

A bonus ingredient often present, and likely to continue into November, is wind shear, or the difference in wind direction from the surface to higher levels of the atmosphere.

Waterspout Formation Graphic
Waterspout Formation Graphic

Passing fronts disturb the wind directions with altitude, creating pockets of rotation. This could lead to waterspouts over the warm, unstable Great Lakes. Boaters should continue to monitor forecasts for this hazard.

THE WARM LAKES WILL ASSERT THEIR INFLUENCE INTO NOVEMBER

Fall-like temperatures and weather patterns are just getting started in the GTA. Temperatures have run above seasonal for the first half of the month in Toronto, even notching a week-long streak of days above 20°C.

Toronto highs through October 16
Toronto highs through October 16

Saturday’s high temperature of 15°C was the closest we’ve seen to average so far this month, but the day still came in above the seasonal temperature of 13°C.

While a break from the precipitation is in the forecast for the GTA’s work week, Ontarians should be on the lookout for these weather systems heading through October and into November. Water takes more time to change its temperature than air, so these atmospheric set ups are likely to persist for some time.