Delaware, ON.
© JordynDelaware, ON.
There were several reports of funnel clouds across southwestern Ontario Monday afternoon.

Conditions were just right for the formation of several funnel clouds across southern Ontario Monday afternoon, prompting Environment Canada to issue a weather advisory for London and surrounding areas, which remained in place until 8 pm.

These types of funnel clouds are generated by weak rotation under rapidly growing clouds or even weak thunderstorms, when temperatures aloft are especially cold relative to the lower levels of the atmosphere.

"This temperature contrast creates instability, which causes clouds to grow vertically and stretches a column of the atmosphere," explains Michael Carter, a meteorologist at The Weather Network.


If there is any weak rotation present, this stretching process can intensify it enough to form a core of low pressure, which causes condensation to occur and water droplets to form. These droplets make the column visible, which is what we see as a funnel cloud.

These funnel clouds at times can reach all the way to the surface and can become either a waterspout or a landspout, with stronger ones sometimes threatening gusty and even damaging winds.


"Landspout tornadoes do not usually cause significant damage but can still be dangerous," said EC in Monday's advisory. "They can be strong enough to topple trees, damage roofs or toss debris short distances."

The advisory also urged people to treat any funnel cloud sighting seriously.

"Should a funnel cloud develop nearby, prepare to take shelter. These funnel clouds usually appear with little or no warning."