Monday, September 16th 2019, 7:30 pm - Sharp-eyed southern Ontarians spotted some ominous clouds on Monday afternoon.
Several funnel clouds were reported swirling over southwestern Ontario during the afternoon and early evening, prompting Environment Canada to issue a weather advisory for the Windsor, Essex, and Chatham-Kent areas.
Observers noted that, apart from the funnel, the weather seemed quite tranquil, and while you might associate funnel clouds with severe weather, they can and do form without strong thunderstorms.
Funnels like those over southern Ontario on Monday aren't the kind that generally result in tornado touchdowns. Rather, these are sparked by weakly rotating updrafts that form in unstable air under cumulus clouds.
In the case of Monday's funnel clouds, warm southerly flow moving over toasty Lake Erie and colliding with cooler air slicing down from the north was the breeding ground for precisely that kind of unstable airmass. As warm air was forced upward by the encroaching cold and afternoon clouds puffed up, conditions were ripe for a few funnels to form.
Thumbnail image: Brooke, Tilbury, ON, Sept 16, 2019.