Severe thunderstorm in Montreal - August 29th, 2018

****I RECOMMEND THE USE OF EARPHONES/HEADPHONES (BASS AMPLIFIED) TO HEAR THE MORE NATURAL SOUND OF THE THUNDER, ALTHOUGH BE CAREFUL WITH THE LOUD SOUND FROM THE RAIN***
A video compilation highlighting fast-moving powerful thunderstorms that affected the SW West Island (and Vaudreuil to Rigaud previously) during the early- to mid-afternoon period.
Thunderstorms were associated with a series of shortwave troughs, and some convergence ahead of a sharp cold front. Ahead of these features, very strong deep shearing fields were present and allowed thunderstorms to move from the WSW to ENE rapidly. At the same time, instability was very high (SBCAPE/MUCAPE of 2750-3000 J/kg) due to strong solar heating by late-morning and surface dewpoints of 23 C. Dry mid-level air and 500 mb SW winds of about 50 knots meant an increased likelihood for locally damaging straight-line winds. A tornado risk, or at least briefly-rotating thunderstorms, also existed before cells merged into a squall line. ***Notice the small bowing segment (like an archer’s bow) on radar imagery as the line of thunderstorms entered the SW West Island, suggesting a higher potential for strong straight-line winds (this is near-similar to the bow that was associated with the wet microburst of August 22nd, 2017). Indeed, at Trudeau airport, and near Sainte-Anne-de-Bellevue, a top gust of 93 km/h was reported, making this likely a wet microburst. Widespread power failures then ensued, especially on the West Island West of there. Rainfall rates were extreme, sweeping the ground like a broom as the wind pushed it at a sharp angle along the gust front. The lightning also eventually became frequent, but the entire event lasted for no more than 17-20 minutes (which is natural, given fast forward motion exhibited by the line). The sound of the rain was fearsome.
I have also supplied some footage of the small branches that snapped from trees, as well as some downed traffic lights, and some signs.
Footage was taken in SW Pierrefonds, located in Montreal’s West Island. Radar imagery is courtesy of NOAA.
~Trav.~