This long-track tornado travelled for 35 km and had a path that was 100m wide. It touched down at 1:30pm, snapping and uprooting trees, damaging and destroying barns, and tearing roofing from houses near the Valens Conservation Area.
Travelling to the southeast, the tornado struck the Lost Forest Trailer Park in Flamborough. There, one trailer was picked up, thrown and totally demolished, leaving nothing but a trail of scattered debris.
A witness captured a photograph of the tornado as it was beginning to rope out near the shore of Lake Ontario in Burlington.
This was one of three tornadoes to touch down in Southern Ontario on August 4; the others were an F1 at Clear Creek and another F1 on Hamilton Mountain.
Figure 2 depicts the surface observations at 2:00 pm, which shows a low pressure system exiting Ontario with a cold front across Lake Erie. The low pressure would have brought southwesterly winds across Toronto and Hamilton, which could have activated the lake-breezes across Lake Ontario. Figure 2 depicts an ongoing thunderstorm over Hamilton (marked as an “R”), which is responsible for this F1 tornado.
According to Environment and Climate Change Canada (2018), an F2 tornado touched down at 1:30 pm EDT near Flamborough, ON. The tornado travelled for 35 km with a maximum width of 100 metres. The tornado caused no fatalities or injuries, but caused $350 thousand dollars in property damage.
Sources
Malseed, B. (August 4, 1999). York University: Tornadoes of Southern Ontario. Retrieved from: http://www.yorku.ca/pat/research/dsills/tornpix/tornadoes.html
NWS Weather Prediction Center Surface Analysis Archive. (2017). Surface analysis 18Z Wed Aug 4 1999. Retrieved from: https://www.wpc.ncep.noaa.gov/archives/web_pages/sfc/sfc_archive.php
Environment and Climate Change Canada Data. (2018). Canadian National Tornado Database: Verified Events (1980-2009) – Public. Retrieved from: http://donnees.ec.gc.ca/data/weather/products/canadian-national-tornado-database-verified-events-1980-2009-public/
