August 3 downbursts confirmed in QC
NTP investigations, including ground/drone surveys, have confirmed three downbursts in southern Quebec with the storms on August 3. Downbursts at Lac Nairne and Grande-Anse (Trois-Rives) had damage rated at EF1. Downburst damage at Sorel-Tracy was rated at EF0.Details are provided in the event summaries below, along with maps and images. The downbursts can be plotted on a map via the NTP Dashboard .
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Event Name: Lac Nairne, QC
Date: August 3, 2024
Start Time: 1:50 PM EDT (1750 UTC)
Final Classification: Downburst (microburst)
Final EF-Scale Rating: EF1
EF-Scale Damage Indicator / Degree of Damage: MHDW/DOD-5
Location of worst damage: 47.6803N, 70.3598W
Description: Tree and structural damage was reported at Lac Nairne (Saint-Aime-des-Lacs) after a storm passed through the area. No injuries were reported. An NTP ground and drone survey was completed on August 7, 2024 documenting intermittent damage over an area approximately 3.0 km long and up to 2.0 km wide, including roof damage to a mobile home. Damage assessed as EF1 downburst (microburst), with an estimated max. wind speed of 140 km/h. Start time is based on witness report. Satellite imagery review is pending.
Event Name: Grande-Anse (Trois-Rives), QC
Date: August 3, 2024
Start Time: 3:45 PM EDT (1945 UTC)
Final Classification: Downburst
Preliminary EF-Scale Rating: EF1
Preliminary location of worst damage: 47.1073N, 72.9198W
Description: Tree damage was reported near Grande-Anse in Trois-Rives after a storm passed through the area. No injuries were reported. Satellite imagery review over a limited area around the reported damage revealed visible downburst damage, impacting an area at least 5.0 km by 3.5 km. Preliminary assessment is EF1 downburst (estimated max. wind speed is pending further review). Start time is radar based.
Event Name: Sorel-Tracy, QC
Date: August 3, 2024
Start Time: 5:39 PM EDT (2139 UTC)
Final Classification: Downburst
Final EF-Scale Rating: EF0
EF-Scale Damage Indicator / Degree of Damage: ACT/DOD-2
Location of worst damage: 46.0263N, 73.1556W
Description: Roof damage to an apartment building and tree damage was reported in Sorel-Tracy after a storm passed through. No injuries were reported. An NTP ground and drone survey was completed on August 7, 2024 documenting intermittent damage over an area approximately 4.8 km long and up to 3.3 km wide, including additional roof damage to a small professional building. Satellite imagery review did not reveal any additional visible damage. Damage assessed as EF0 downburst, with an estimated max. wind speed of 130 km/h. Start time is based on witness report.
Regional map showing the Quebec locations of the three downbursts from August 3.
Survey map showing the extent of EF1 downburst damage at Lac Nairne, QC.
Drone photo showing the worst downburst damage - major loss of roof covering for double-wide mobile home.
Drone photo showing location with numerous trees uprooted by the EF1 downburst at Lac Nairne.
Planet.com satellite image showing the Grande-Anse area before the downburst.
Planet.com satellite image showing the Grande-Anse area after the downburst with numerous swaths of tree damage at centre of image. Trees were also reported down along Route 155.
Survey map showing the extend of EF0 downburst damage at Sorel-Tracy. Additional light damage was found within oval but is not shown on map.
The worst damage with the downburst at Sorel-Tracy was a removed apartment building roof covering (newly replaced at the time of the survey).
Roof covering removed from commercial building at Sorel-Tracy.
