The power of the 2023 Atlantic hurricanes depends on the outcome of El Niño in the face of global warming

HALIFAX – The Canadian Hurricane Center is predicting an “average” season, saying the ferocity and frequency of tropical storms off Canada’s east coast this year will be decided by competing factors in global weather.

Meteorologist Bob Robichaud said during a briefing Thursday that much depends on whether this season’s El Niño, characterized by above-average water temperatures in the Pacific Ocean, has its usual calming impact on Atlantic waters.

Robichaud says that in El Niño years, high-altitude winds blowing out of the Atlantic Ocean have lessened the number of storms in the waters off Canada’s eastern coasts.

Warmer El Niño waters cause warmer air over the Pacific to rise higher into the atmosphere, creating strong upper-level winds that can decapitate storms as far away as the North Atlantic. It is a phenomenon known as wind shear.

On the other hand, the eastern Atlantic is already warmer than usual this year, with forecasters noting temperature increases of 1-2C above the 30-year average.

“We expect it to get hotter over the course of the next few months,” Robichaud said.

He said most research indicates that warmer Atlantic waters make storms stronger and better able to withstand El Niño wind shear.

But which of the two factors, El Niño and the warming of the Atlantic, prevails will only become clear at the peak of the hurricane season in August, September and October, Robichaud said.

“We have two competing factors that will determine the level of activity in the Atlantic Ocean this year,” Robichaud told reporters. “Which turns out to be dominant remains to be seen.”

Earlier Thursday, the US-based National Oceanic and Atmospheric Administration also predicted an average season, with 12 to 17 named storms, five to nine hurricanes, and one to four major hurricanes, generating winds greater than 177 km. /h.

Robichaud said the agency’s numbers are in line with historical averages of 14 named storms, seven hurricanes and three major storms during the June 1-Nov. 30 Atlantic season.

He said this year’s predictions have a “very wide range” because of the competing weather phenomenon that is about to unfold over the course of the summer and early fall.

“The forecast is really for a season, in terms of the number of named storms, which is close to average for a typical hurricane season,” he said.

But he added that it only takes one storm to wreak havoc, recalling that Hurricane Fiona claimed three lives, destroyed homes and knocked out power to more than 600,000 homes and businesses when it made landfall in the Atlantic region on September 24, 2022.

“In any given year, there is a chance of having a storm of this nature,” Robichaud said.

Fiona became the seventh costliest extreme weather event in Canadian history and the costliest in Atlantic Canada. The Canada Insurance Bureau estimated that it caused more than $800 million in insured damage.

Fiona remained a powerful storm in part due to a low pressure trough moving into Atlantic Canada just as it came ashore, causing the storm to re-intensify.

While forecast centers produce yearly predictions for the number of storms, science hasn’t gotten to the point where forecasters can provide long-range forecasts for how many of them will make landfall and cause the kind of damage Fiona did.

Robichaud said that attempts are being made to forecast the likelihood of the hurricanes heading into Atlantic Canada rather than moving away, but at this point the research is not complete.

This report by The Canadian Press was first published on May 25, 2023.

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