How Fiona became a record-breaking Canadian storm

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 the most powerful and destructive storms in Canadian history.

Extreme wind gusts of 179 kilometres per hour were 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, a buoy 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.

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.

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 temperatures last summer were well above average, in the high 20s just to our south. 

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.

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 3 hurricane filled with warm air merged 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.