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‘Atmospheric river’ brought Nanaimo one of its wettest days on record

Close to 78 millimetres of rain fell on Nov. 14, says Environment Canada
An ‘atmospheric river’ event saw 77.8 millimetres of rain dumped on Nanaimo on Nov. 14, good enough for sixth-wettest day in recorded history, says a meteorologist from Environment Canada. (Tyler Hay/Black Press Media)

The deluge from this past weekend’s ‘atmospheric river’ led to record-breaking rainfall in the Harbour City, according to an Environment Canada meteorologist.

A rainfall warning was issued for the area last Saturday. Armel Castellan, Environment Canada meteorologist, told the News Bulletin that the “bull’s-eye” was the “southern third” of Vancouver Island, but Nanaimo had 47.4 millimetres on Nov. 13, followed by 77.8mm on Nov. 14 and 16.9mm the morning of Nov. 15.

The 47.4mm on Nov. 13 broke a previous daily record of 32mm in 1954, while the 77.8mm on Nov. 14 surpassed a previous record 67mm from 1983 and made it the sixth-wettest day on record, Castellan said.

He said the 142.6mm of rainfall from Nov. 12-15 represented more than 70 per cent of a typical November in Nanaimo.

”We are already at 284mm this month. Nanaimo gets 197mm for November on average, that’s a climatological average over 30 years. So far this month – and we’re only halfway through it – we’ve seen 144 per cent of normal rain,” Castellan said. “If I were to add September and October to that analysis, Nanaimo would normally have seen 335mm for [September-November]. You’re now at 545mm, so that’s 163 per cent of normal so far this fall.”

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In comparison, Castellan said Victoria is at 225 per cent rain for the same time frame, while Chemainus is close to 200 per cent.

“Atmospheric river” is a relatively new term, said Castellan, but the event has been occurring for many years.

“They’re just now getting a little bit more concentrated and potent and longer lasting just for various reasons related to climate change,” said Castellan. “They’re kind of like a narrow corridor of ultra-moist moisture that’s coming up from the sub-tropics. We call them sometimes ‘Tropical Punch’ or ‘Pineapple Express’ because they come from the direction of Hawaii. They’re able to hold all this water vapour and it’s literally equivalent to five Mississippi Rivers in and of itself, if it’s a really good strong, potent plume.”

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The total rainfall on Nov. 14 was close to the daily record for any November day, which, according to Castellan, was 84.1mm from Nov. 2, 1955.

The flooding that resulted from the heavy rains led the Regional District of Nanaimo to declare a state of local emergency and issue evacuation orders in parts of Cedar on Monday. The City of Nanaimo stated in a press release that it experienced “localized flooding” in some areas.

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Karl Yu

About the Author: Karl Yu

I joined Black Press in 2010 and cover education, court and RDN. I am a Ma Murray and CCNA award winner.
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