Flooding at Pinson’s Corner. (Photo by Shawn Wagar)

Flooding at Pinson’s Corner. (Photo by Shawn Wagar)

Intense November rains wallop Chemainus Valley with 481.9 mm

Floodgates open with a new all-time 24-hour rainfall total set Nov. 14-15

The weather floodgates opened during November and engulfed the Chemainus Valley with 481.9 millimetres of precipitation by the time the month was done.

“The Chemainus weather station received a record 2 1/2 times the normal monthly rainfall for November,” noted Chris Carss, a volunteer recorder/observer for Environment and Climate Change Canada. “The rain fell with a frequency that was hardly any more than the normal number of wet days at this time of year, but the precipitation was often very intense when it occurred.”

No all-time records were set, but a couple of November marks were shattered.

Carss pointed out a record was established for a 24-hour rainfall in November with a total of 98 mm from 3 p.m. Nov. 14 to 3 p.m. Nov. 15. That broke the old mark of 85.1 mm. set on Nov. 7, 1995.

The total November ‘95 rainfall of 364.4 mm was also exceeded by nearly 120 mm.

“November’s unprecedented rainstorms introduced many of us to a seemingly new term, atmospheric river,” Carss added. “In fact, it is an update first proposed about 30 years ago of an older more familiar term, pineapple express, that long but comparatively narrow stream of clouds and heavy rain that is sometimes carried northeast from the Hawaiian tropics to the Pacific Northwest.

“The name change, which has only recently been picked up by the mass media, can be attributed to global warming which is increasing the intensity and distribution of these streams. The result of this increased intensity has been, and will sometimes continue to be, the torrents of rain this past month that have caused so much destruction. And the Chemainus Valley didn’t receive the worst of it in British Columbia. Areas of the west island and Fraser Valley got it worse than us.”

The other departure from normal, Carss observed, was the mean daily minimum temperature. It was only a half degree above normal, but that was just enough to keep the entire month rainy with no snowfall recorded at any time.

The other main weather elements were close to normal, including the mean daily maximum temperature of 9.0 degrees Celsius (normal 9.1 C), and days with sunshine.

Temperatures did vary a great deal during the month, however, with an extreme maximum of 14.5 C on Nov. 4 and extreme minimum of 1.0 C on Nov. 17.

On Thetis Island, Keith Rush recorded 376.3 mm of rain at his Foster Point River residence, as he jokingly referred to it rather than a road.

Rush noted it was the “wettest November by over 100 mm and my second wettest month recorded behind January 2020 at 379.7 mm.”

There was far less rain in November 2020 on Thetis, 209.9 mm, and the average for the month there is a low 185.7 mm by those standards.

”At the beginning of November, there was considerable uncertainty as to what to expect for that month,” Carss recalled. “September had seen about four times the normal monthly rainfall right after an exceptionally dry spring and summer, and October had about twice the normal amount of rain. A third straight month of heavy rain of double the normal amount was unprecedented and seemed unthinkable, but it happened.

“It now seems clear that six months of exceptionally dry weather are being followed by at least six months of exceptionally wet weather. It further appears the heavy precipitation will be accompanied by frequent below normal temperatures at the very time we could use a bit of regional, if not global, warming. This is raising the prospect of some highly disruptive and possibly damaging snowstorms during the upcoming winter and possibly continuing into early spring as it did back in early 2008.”

B.C. Floods 2021Severe weather

 

Extensive flooding happened again in November throughout Westholme. (Photo by Shawn Wagar)

Extensive flooding happened again in November throughout Westholme. (Photo by Shawn Wagar)