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How a weather ‘triple whammy’ enabled the Fort McMurray fire

Environment Canada climatologist David Phillips crunched the historical weather data for Fort McMurray and turned up some disturbing trends


 
A massive plume of smoke rises from a wildfire burning out of control near the highway to Fort McMurray, Alberta Friday, May 6, 2016.THE CANADIAN PRESS/Ryan Remiorz

A massive plume of smoke rises from a wildfire burning out of control near the highway to Fort McMurray, Alberta Friday, May 6, 2016.THE CANADIAN PRESS/Ryan Remiorz

“It was a triple whammy,” says David Phillips, senior climatologist at Environment Canada. He’s referring to the weather that precipitated the huge forest fire at Fort McMurray, Alta. At Maclean’s request, Phillips crunched the city’s weather data, which started in 1944. He discovered a disturbing trend: winters are dramatically drier, and warmer than they were 50, even 70 years ago. The past few months, meanwhile, pulverized winter records. The worrisome climatic conditions in northern Alberta created the perfect environment for a massive conflagration. All it needed was a spark.

Fort Mac weather

The first factor was precipitation, or the lack of it. The winter months from October to April were the driest on record, recording just 61 mm of melted snow and rain. The normal is more than double that, at 132 mm, while the previous record low for the same seven-month period occurred in 1946, when just 84 mm fell. “In a profession that measures new records in percentages of millimetres,” he says, “it smashed the previous one.” Alarmingly, the new record low is 27 per cent drier than the previous record.

The situation only got worse as the spring proceeded. Between April 15 and May 8, a period of 24 days, there was one millimetre of rain. The norm is 21 mm. Instead of seven or eight days of rain, there was just one.

The second factor was temperature. The seven months since October 2015 were the second-warmest on record, with an average temperature of -4.5° C.  In contrast, the normal is -7.9° C. (The warmest on record was 2005-06 at –4.2° C). As if that wasn’t enough, Phillips also looked at the temperatures in the period from Jan. 1 to May 5 for every year, starting when records began in 1944. Before this year, the warmest day from Jan. 1 to May 5 in Fort McMurray was 30.6° C on May 2, 1980. That record tumbled last week, which recorded the two hottest days for that period. May 3, 2016 clocked in at 32.6° C (it also smashed the old May 3 record from 1945 of 27.8 degrees) while the next day, May 4, saw thermometers rise to 31.7°  (which broke the previous May 4 record of a mere 27.6°  in 1992.)

Then came the third factor: the “spring dip.” It’s the time between the disappearance of snow on the ground and when the trees gain their leaves. The spring dip is when the moisture content in trees is at its lowest. There was no snow since February, Phillips notes, letting the forest floor dry out all March and April.

The stage was set for a fire. Agencies in Alberta started their preparations earlier than usual. Everyone knew it was going to be a bad season. They just didn’t know where the first big one would strike, and when. It arrived on Sunday, May 1, just southwest of Fort McMurray.

Maclean’s is answering all your questions about the Fort McMurray fire. Read our FAQ here.


 

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