Monday, August 15, 2016

Heavy rain from Louisiana to Quebec and Ontario

Historic flooding across Louisiana has resulted in at least four fatalities and thousands of evacuations and water rescues. (Photo via Twitter @cbcnews)
What a difference a few hours can make when it comes to the weather. In less than 48 hours, many portions of southern Quebec and eastern Ontario recorded more rain than in the previous six weeks. Heavy tropical rains, along with embedded thunderstorms, swept along the edge of a large Bermuda high to our southeast. Southern Quebec reported 50 to 100mm (2 to 4 inches) of rain over the weekend, the heaviest along the Ottawa Valley, through Montreal and into the Townships. Here on L'Ile Perrot, I measured 78mm from late Friday to early Sunday. That included nearly 27mm in just a couple of hours, during a thunderstorm early Sunday morning. The normal monthly rainfall in August is 94.1mm for Montreal. Some severe weather was also observed, with tree damage in the eastern Townships, as well as minor flooding being reported. In Ontario, at least two tornadoes were confirmed on Saturday, including an EF-1 (150 to 175km/h winds) along the shores of Lake Simcoe.

The soupy weather across eastern North America is the result of a large Bermuda high sitting off the east coast of the US. This system is pumping extremely warm and humid air north and west. Searing heat has been gripping the large east-coast cities of the US, as well as southern Ontario. We had a break on Saturday, as clouds and rain managed to keep the temperatures down here in Montreal. Along the edge of the high is a conveyor belt of moisture running from the Gulf of Mexico into Quebec. Therefore the closer to the Gulf, the more rainfall. Unprecedented historic flooding is occurring in Louisiana, with a least four fatalities reported. Thousands of water rescues have occurred, in addition to tens of thousands more evacuated. The flooding was the result of nearly 2 feet of rain in less than 48 hours. Damage is widespread across the state, including the closure of Interstate 10.

After the severe drought conditions of the last month, more rain is expected in southern Quebec late Tuesday and Wednesday, with perhaps another 25 to 50mm. Temperatures will warm up again for Monday, reaching 28C (83F) this afternoon in Montreal.

No comments: