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What constitute's severe weather in Alberta's hail alley

Innisfail's July 12 storm on the 'pretty low end,' says Environment Canada meteorologist

INNISFAIL — Extreme weather watchers and storm chasers might consider setting up base in the area.

“Innisfail’s probably one of the better locations to set up your camera,” says Dan Kulak, meteorologist with Environment Canada, who detailed what constitutes a severe storm following the Sunday, July 12 hailstorm that swept through the area from the west.  

“If you’re looking to see hail like that somewhere in Alberta, Innisfail and Red Deer areas is probably one of the more likely areas to get storms like that — the hail alley between basically Calgary and just north of Red Deer,” said Kulak during a phone interview.

“That central part of Alberta is part of hail alley — it’s probably the heart of hail alley,” he said.

Over the last couple of weeks, hail has hit the area, including in Bowden, Sundre, Olds and Innisfail.

On Sunday, July 12, Innisfail was hit with roughly 26-millimetre (mm) diameter hailstones, with nearby areas like Caroline reportedly receiving 24 mm stones, as well as Eckville, Olds and west of Sundre all seeing about 21 mm hail. Spruce View had 30 mm hail, he said.

“These are all public reports — you really don’t have Environment Canada staff out there with calipers measuring this stuff. This is what people send in to us, and we trust it at face value, basically.”

Nickel-sized hailstones are about 21 mm in diameter, he said.

“For our severe thunderstorm criteria for hail, we need to have at least 20 millimetres of diameter before we call it a severe storm,” he explained, adding a storm would be considered severe even if only one single stone fell into a backyard.

Storms are also considered severe when winds reach 90 kilometres per hour or when precipitation reaches at least 50 mm, or a couple of inches, in one hour, he said.

“Doesn’t have to be all three. Sometimes it is all three, but only needs to have one of those three — the rain, the hail, or the wind — to meet criteria for us to classify it as a quote-unquote severe storm.”

Naturally, tornadoes are also a subset of severe weather events, he said.

As a point of interest, he added that July 14 marked “the 20th anniversary of the Pine Lake tornado that killed 12 people and was the fourth deadliest documented tornado in Canadian history.”

While not unheard of, there were no golf ball-sized stones, measured at 44 mm, that hit Innisfail on July 12.  

“Sometimes, you get tennis balls, which are 2.5 inches, or 64 millimetres,” he said.

While people who see such storms might consider them a once-in-a-lifetime or extremely rare experience, Kulak said they’re not altogether that uncommon.

“From a meteorologist’s perspective, it’s just another storm. But the insurance people, and the public, will say holy crap, ‘I’ve never seen a storm like that in my life.’ Because you’ve never been under one, but they are around.”

He said the question breaks down into two considerations: how often do such storms happen to people, and how often do they actually happen in unpopulated areas.  

“When they intersect, then you have these big problems.”

The July 12 storm was, compared with the average, on the “pretty low end,” he said.

“That is the challenge with the summer weather and saying how normal is it? Most of the storms don’t hit anything, they go through the middle of nowhere,” he said, adding data is only available where there are monitoring stations.

Storms that unleash a punishing plethora of tennis ball- to even grapefruit-sized hail are not necessarily completely unusual for the province, he said, adding there are “the proverbial handful of days — three or four days — per year, where you are going to get reports of that size of hail from somewhere in Alberta.

“Most of those things don’t make a lot of news because they happen in areas where there’s no infrastructure, there’s no people.”

Refering to the major hailstorm that devastated parts of Calgary last month, he said, “had the storm gone just five kilometres to the east or 10 kilometres to the north, we wouldn’t be talking about the fourth most impactful (weather) event in Canadian history.”

He encourages people not to dismiss or downplay weather watches, which are typically issued hours in advance of a potential storm. Those do not of course always result in a major storm, but by the time a severe thunderstorm warning is announced, “it’s too late to prepare,” he said.

“Storms can develop so fast…a warning is your last line of defence, not your first.”

The watch warning went out just after 8 a.m. on July 12, with warnings being issued later in various parts of Central Alberta before noon, continuing throughout the afternoon as the storm moved along, he said.

“The key there is to understand that the weather is around you. Awareness is not just about what you’ve experience, it’s about what can happen in your area.”

Additionally, he wanted to stress the fact that even though tornadoes, hail, wind, and heavy precipitation represent a major threat when such storms hit people or infrastructure, “lightning kills more people per year in Canada than all of the other stuff put together. People underestimate the deadliness of lightning.”

Most of these fatalities occur from storms in which no warnings were issued, he said.

Since people are used to seeing lightning during even lighter storms, some might for example decide to try and finish up chores in the backyard or finish a round of soccer before heading inside, he said.  

“The big storms drive people inside because of all the other awareness activities around them. The small storms don’t drive people inside, and the lighting from those are killing people, because they remain vulnerable because they don’t feel the threat.”