"The good news for all Canadians is that there's no area of significant population where we're showing colder than normal," Dave Phillips told CBC News on Tuesday.
Environment Canada's supercomputer in Montreal has run the numbers, and Phillips said that except for a small area around Lake Superior and part of Nunavut, the winter will be warm in contrast to last year's — one of the longest and coldest on record.
Phillips said the forecast model for December, January and February shows warmer than normal temperatures from Vancouver Island almost to Lake Superior, including in Yukon and the Northwest Territories. Much of Atlantic Canada is also expected to be warmer than normal.
Ontario and Quebec are expected to have a more typical winter than last year — less consistent snow and cold, more abrupt weather changes from day to day.
The main reason for the warmer forecast is El Nino, the warming of Pacific sea-surface temperatures that occurs ever four to 12 years.
The Australian Bureau of Meteorology said Tuesday that temperatures in the Pacific have already exceeded the ElNino threshold, but measures of Pacific air pressure fluctuations have yet to breach it.
Or as Phillips puts it, the water and the atmosphere typically dance together. So far the atmosphere is shrugging the water off.
Polar vortex had 'no predators'
The apparent arrival of El Nino increases the odds that the polar vortex will be less of a factor this winter — either keeping it in the north or making it less intense.
El Nino also makes the forecast more likely to be accurate — pushing its certainty from 60-something to as high as 80 per cent, Phillips said.
He said the forecast is useful to farmers or groups that need to plan responses to floods or forest fires, but that it would be unwise for anybody to bet the family farm on it.
Phillips said Environment Canada — whose one-day forecasts are 93 per cent accurate — could keep the relatively uncertain seasonal forecast to itself, but that Canadians love it.
"For the general public, my god, it is the most sought after thing," he said. "They wait for it with bated breath. And what are they going to do with it? Nothing."
Phillips said he remembers when the seasonal forecast involved people sitting in a room and hashing out a best guess based on previous winters. With improved data, he expects forecasting to continue to improve.
"The oceans can't burp without us knowing about it now," he joked.
The agency will never be able to do a daily forecast far into the future, but he said it should be able to fine-tune its seasonal forecasts to the point where there would be five possible categories, instead of the current three (below average, average, above average).
The Weather Network released its long-term forecast last week, predicting colder temperatures than Environment Canada is but less frigid temperatures than last winter.