How Fiona became a record-breaking Canadian storm - Action News
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Nova ScotiaCBC Explains

How Fiona became a record-breaking Canadian storm

One year ago, the atmospheric and oceanic ingredients came together to produce a powerful storm with the lowest recorded landfall pressure in Canadian history.

Warm sea surface temperatures and the storm's track all played a role

Extensive damage to homes after a storm.
This aerial drone photo shows extensive damage to homes in Port aux Basques, N.L., on Sept. 26, 2022. (Yan Theoret/CBC)

A little over a year ago, on Sept.14, 2022, Fiona became just another named tropical storm tracking through the Caribbean.

Ten days later, Fiona became one of themost powerfuland destructive stormsin Canadian history.

Extremewind gusts of 179 kilometres per hourwere recorded at Arisaig, N.S., with widespread, damaging gusts over 130 kilometres per hour clocked across much of eastern Nova Scotia, Prince Edward Island and southwestern Newfoundland

As Fiona rolled in with a huge storm surge and massive waves, abuoy offshore recorded a significant wave height of 17 metres, and a peak wave of 30 metres. That's the length of three school buses.

That wall of water and those significant waves pushed into Cape Breton, the Gulf of St. Lawrence and southwestern Newfoundland with devastating consequences.

Peak winds with Post-Tropical Storm Fiona reached 150 to 180 km/h.
Peak winds with post-tropical storm Fiona reached 150 to 180 kilometres per hour. (Ryan Snoddon/CBC)

So how was the storm able to remain so strong as it moved into Atlantic Canada and what made it so destructive?

While more in-depth scientific studies will be completed over the next few years, here are some of the factors that we already know played a huge role.

Warm sea surface temperatures

No storm can be directly attributed to climate change, however if you're looking for the most direct link with Fiona, look no further than the ocean.

Hurricanes fuel themselves in waters over 26.5 C or warmer and sea surface temperatureslast summer were well above average, in the high 20s just to our south.

Warmer than normal sea surface temperatures played a key role in Fiona maintaining its strength as it tracked northward.
Warmer than normal sea surface temperatures played a key role in Fiona maintaining its strength as it tracked northward. (Ryan Snoddon/CBC)

Unfortunately, Fiona tracked right through the warmest of those waters over the Gulf Stream and the storm was able to retain major Category 3 status until just hours from landfall.

Post-tropical transition

Every hurricane or tropical storm that moves northward into the higher latitudes eventually undergoes post-tropical transformation.

Instead of getting fuel from the water, these storms shift gears and fuel themselves from temperature differences in the atmosphere, the same way everyday low pressure systems and mid-latitude storms do.

In the case of Fiona, the Category 3hurricane filled with warm airmerged perfectly with an incoming cold front just as it began its post-tropical transition.

The large temperature contrasts between the hurricane and the cold front allowed the storm to become an extremely powerful post-tropical storm just as it rolled into Atlantic Canada.

When Fiona made landfall in eastern Nova Scotia it became the lowest pressure ever recorded on land in Canada at 931 millibars.
When Fiona made landfall in eastern Nova Scotia it became the lowest pressure ever recorded on land in Canada at 931 millibars. (Ryan Snoddon/CBC)

AsFiona made landfall in Nova Scotia, it set a new record as the lowest pressure ever recorded on land in Canada at 931 millibars.

The track

"What if"is a question that comes up a lot after storms roll through.

What if the track was further west or east?

In the case of Fiona, given the size and strength of the storm, there would have been no ideal track.

However, as mentioned above, the path it did take allowed it to remain a hurricane for longer before it became apost-tropical storm.

For P.E.I. and the Northumberland Shore of Nova Scotia, this storm brought the destructive combination of heavy rain, some of the most damaging winds and relentless storm surge.

A person stands on a Charlottetown street on the day after Fiona. A massive tree blocks the entire road.
Many large, historic trees came down in Charlottetown during post-tropical storm Fiona. (Jesara Sinclair/CBC)

My colleague in P.E.I., meteorologist Jay Scotland, says the 60 to 100 millimetresof rain that fell across the island essentially liquefied the rich red soil.

As winds gusted well over 100 kilometres per hour for hours on end, trees that didn't break from the wind instead toppled over, as their entire root structures lifted out of the ground.

Some locations saw more than 10 hours of winds gusting over 100 km/h
It wasn't just the strength of the winds, but the duration of them that made Fiona so extreme. (Ryan Snoddon/CBC)

The fact that the strongest winds were from the north meant P.E.I.was completely exposed as they howled in from the open Gulf of St. Lawrence.

It was a similar story along the Northumberland Shore of Nova Scotia, where saturated soil and some of the most extreme winds downed thousands of trees and numerous power poles and lines.

Remnants of Big Island road after Hurricane Fiona.
Remnants of Big Island road in Pictou County, N.S., after Fiona rolled through. (Submitted by Lynn Arsenault)

P.E.I., the NorthumberlandShore and also southeastern New Brunswick also took the brunt of the greatest storm surge.

The extreme and relentless northerly winds pushed a massive amount of water from the gulf into the coastlines which caused massive coastal erosion and destruction to infrastructure.

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Structures along the coast in Caissie Cape, N.B., sustained heavy damage during post-tropical storm Fiona. (Aniekan Etuhube/CBC)

The track of the storm over Cape Breton aided in the push of storm surge and significant waves into Port aux Basques, N.L., with catastrophic damage.

My colleague in Newfoundland and Labrador, meteorologist Ashley Brauweiler, has been speaking with a few scientists about the impact in Port aux Basques and what happened there.

Drone video shows devastation in Port aux Basques, N.L.

2 years ago
Duration 0:53
Footage shot over Port aux Basques, N.L., shows the damage caused by post-tropical storm Fiona.

While only a theory, the consensus is that due to the storm surge and high waves, the water was able to crash and roll over the Channel Head and essentially became trapped. Before the water had time to drain away and escape, yet another wave came crashing in.

The Channel Head at Port aux Basques may have trapped water and added to the high water levels during the storm.
The Channel Head at Port aux Basques may have trapped water and added to the high water levels during the storm. (Ryan Snoddon/CBC)

This happened again and again, causing water levels to rise and bringing those massive, destructive waves into shore where they washed away homes.

Between its track, the way the hurricanetransitioned to a post-tropical and the warm ocean temperatures that fuelled it, Fiona became a storm for the history books in Atlantic Canada.

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