Severe Thunderstorm/Supercell in Montreal - June 5th, 2021

***I STRONGLY RECOMMEND USING EARPHONES/HEADPHONES (BASS AMPLIFIED) TO HEAR THE MORE NATURAL SOUND OF THE THUNDER/RAIN***

A present here a video compilation of a supercell thunderstorm that affected the West Island of the island of Montreal before advancing into the South Shore. A separate thunderstorm affected the East End and Greater Montreal before moving East.

Thunderstorms were sparsely-distributed but were associated with a robust shortwave trough and some lift associated with an attendant cold front. While much of the day was spent until a cloud cover from early-day convective rainfall ahead of these features, some morning sunlight and re-emerging breaks in the cloud deck by mid-afternoon allowed for sufficient destabilization that had contributed to a moderately unstable environment. Early-day rainfall served to moisten the air further, which had eventually induced borderline high to very high humidity. Deep shearing fields were additionally favorable for the development of supercell thunderstorms with the initial thunderstorms that formed. Indeed, as the thunderstorms that affected this general area this late-afternoon were discrete, there was some opportunity for transient rotation, which had been observed over the SW portion of the West Island (the mesocyclone manifested at the left of the supercell in this video) before becoming lesser defined. The supercell thunderstorm also split into two separate thunderstorm cells – the right-moving cell advancing towards the East (please refer to supplied radar imagery to see this phenomenon). Following this, torrential rainfall and strong outflow winds began, with a moderate lightning frequency (some lightning strikes, as always, were missed in the video). Combined with the early-day convective rainfall, 14.8 mm of rainfall was observed at Trudeau airport, and 17.2 mm at Sainte-Anne-de-Bellevue (closer to where I reside), most of which fell in just under 85 minutes during the thunderstorm. By drastic comparison, only 2 mm was observed farther East, over greater Montreal, and only 1 mm even farther East of there, towards Longueil-Saint-Hubert. Our electricity was very briefly lost (just barely under one minute in duration) during this portion of the thunderstorm.

Footage was taken in SW Pierrefonds, located in Montreal’s West Island. Radar imagery is courtesy of NOAA.

~Trav.~