***I STRONGLY RECOMMEND USING EARPHONES/HEADPHONES (BASS AMPLIFIED) TO HEAR THE MORE NATURAL SOUND OF THE THUNDER***
A video compilation showing a mid-afternoon isolated thunderstorm, followed by a late-afternoon severe thunderstorm, affecting the SW West Island of Montreal of Montreal. This was the second thunderstorm day for the island of Montreal (third for the general area) for October, and only three days after the previous event. This is quite rare, especially in terms of the environment featured by this day (October 10th).
The thunderstorms were associated with a sharp cold front and favorable lift supplied by an amplified mid-level trough. While instability was fairly low, overall, the extent of the instability gradually was vertically steep enough as it became more surface-based to support the deeper convection necessary for lightning production. Sufficient solar heating, steep mid-level cooling rates and moderate humidity combined to create this sufficiently deeply-distributed instability. Deep shearing fields were further present and largely unidirectional in orientation but were very much enhanced in response the mid- to upper-level WSW flow. This flow, together with steep cooling rates aloft, increased the likelihood for strong to locally damaging straight-line winds under the linear thunderstorm modes during the late-afternoon. Radar signatures also suggested some embedded rotation within the line, near Joliette, by late-afternoon. The video shows the strong downbursts (especially during the first thunderstorm), lightning, and heavy rains mixed with pea-sized hail (identified by the tapping noise on the window, and ice matter bouncing off the edge, and off the ground). Lightning frequency was mostly moderate (low with the first thunderstorm), but with principally low-energy intra-lightning occurrences (i.e. in-cloud lightning). A nice cloud-to-ground strike was observed over the West Island (Ile-Bizard) during the first thunderstorm. Eventually, a severe thunderstorm warning was released (a watch was released by late-morning) for the late-afternoon thunderstorm line.
Footage was taken in SW Pierrefonds, located in Montreal’s West Island. Radar imagery is courtesy of NOAA.
~Trav.~
Негізгі бет Severe thunderstorm in Montreal - October 10th, 2020
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