BC Storm Damage is Extreme

November 17, 2021

Jeff Masters in Yale Climate Connections:

An intense low-pressure system brought an atmospheric river of water vapor and torrential rains to southern British Columbia and northwestern Washington state on Monday, generating devastating flooding that virtually isolated the city of Vancouver from the rest of Canada. The floods came less than five months after the most extreme heat wave in global history affected the same region, fueling destructive wildfires.

Flooding and landslides from Monday’s storm cut the three main highways connecting the city of Vancouver, located on the Pacific coast, with the interior portions of Canada. Damage to some of these highways was extreme, and will result in months-long closures. In addition, all rail access to Vancouver was cut by the flooding, with closures expected to last days or weeks. These closures may have significant impacts on the Canadian economy, since the Port of Vancouver is the largest port in Canada, and fourth-largest in North America. Canada is one of the world’s largest grain exporters, and the flood damage will interrupt exports of wheat and vegetable oil, potentially causing a rise in global food prices, which are already at a 46-year high.

On Monday, a large swath of southern British Columbia recorded four to 10 inches of rain in 24 hours, setting numerous records for most precipitation in a day. One of the highest 24-hour amounts observed was 11.59 inches (294.3 millimeters) in Hope, British Columbia.

The heavy rains fell on mountainous areas that, in many cases, had been denuded of vegetation by the destructive wildfires that ravaged the region in late June and early July. These wildfires had been fueled by a record heat wave that brought an insane temperature of 49.6 degrees Celsius (121°F) to Lytton, British Columbia – the hottest temperature ever recorded in Canada. A rapid-response study from the World Weather Attribution program found that this heat wave would have been “virtually impossible without human-caused climate change.” The study estimated that the event was roughly a 1-in-1000-year event in today’s climate, but added, “the observed temperatures were so extreme that they lie far outside the range of historically observed temperatures. This makes it hard to quantify with confidence how rare the event was

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