It has been a very active summer in the prairies, and we aren't done yet. At the time of writing on July 21, Alberta has already surpassed its annual average of 15.4 tornadoes based on the 1980-2009 climatology, which may have already been skewed a little high compared with recent years based on the active 80s.
Here are two tornado events in Alberta and one straight-line wind event in Saskatchewan that occurred in mid-July.
Crossfield, AB - July 14
A classic central Alberta severe weather day was expected on this day, with the focus of severe weather in Alberta expected through "hail alley" - just north of Calgary. A group of us sat just south of Crossfield, and watched as thunderstorms initiated early along the foothills to the west during noon hour. These messy-looking storms would generate an outflow boundary that would drift east toward the QE2 corridor, and become somewhat restrained by large-scale southeasterly flow. Rapid cumulus development ensued, with a line of towering cumuli sitting atop the low level convergence axis - and it didn't take long before we spotted a couple of vorticity funnels along the base. Further north, inflow features began streaming into an increasingly dominant updraft base, with a small notch developing to its west. We repositioned a few kilometres north, before a large funnel appeared in the notch, at the occlusion of a wrapping rear-flank downdraft. It wasn't long before a tornado spun up a couple of miles to our NNW, which wasn't fully condensed - but was associated with a dust whirl at the surface. It quickly became obscured in the rain, but continued for some time. The parent storm fought its outflow as it tracked east, but was the most prolific vorticity funnel producer I've ever witnessed, with several funnels sometimes occurring simultaneously along the shelf generated by the gust front.
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| The Crossfield tornado. Storm structure reveals it was mesocyclonic, despite numerous other nonmesocyclonic funnels occurring with the storm. |
Based on the damage path, the tornado cut a swath mainly through maturing wheat and barley crops, from NW to SE, beginning at 2:09PM MDT. To this day, it maintains its preliminary EF0 rating. However, damage suggests it could have been slightly more intense in my opinion (EF1), due to a holiday trailer being dragged and thrown 87m (determined by GPS) uphill to the southeast. A lack of damage indicators for vehicles makes an estimate of tornado intensity trickier in this case. The tornado spun up essentially right in the backyard of someone's property, where it sucked a horse trough dry of water, before impacting the RV and flattening a narrow swath of crops to the southeast. The crops would eventually stand up again (as observed in subsequent days), but a high translational speed compared with a relatively low rotational velocity likely resulted in the focused convergent pattern of crop material that was impressive to see firsthand.
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| Apparently toilets are well-bolted. They always seem to survive! |
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| Gouge marks are evident where the trailer scraped along the ground, before being deposited in the opposite ditch. |
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| Very impressive track as seen from the air. The track width was no more than 20-30m. |
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| A close-up of the convergent pattern in bearded wheat. |
Here is a
link to a story I made for this tornado.
Eston, SK - July 14
On the same day as the Crossfield tornado, other storms occurred further east across SE Alberta and into Saskatchewan. After abandoning the original Crossfield storm, we tracked another hailer south of Oyen, before noting explosive development of another storm to our east near Eatonia in SW Saskatchewan. This storm would go on to clobber the town of Eston, with street flooding, wind-driven hail that damaged siding, roofs, cars, and crops; and intense straight-line winds that caused significant damage particularly on the SW corner of town.
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| The storm as seen from the west that would go on to impact the town of Eston. Atom bomb vibes. |
Some folks in town thought a tornado had come through due to how intense the winds were. Others were okay with the official designation of straight-line winds, which have been called "plough winds". In my opinion, the damage incurred suggests at least EF1 intensity (135-175km/h) wind gusts. One resident showed me a video of the storm structure before it impacted the town, which revealed a descending precipitation bomb characteristic of an incipient downburst - and no evidence of funnel clouds. The consistent and widespread west-to-east damage also suggests it was a downburst - though I couldn't determine if it exceeded the scale of the designation of a microburst (damage over a width of <4km). Of note, a hangar at the airport was completely destroyed, with debris being thrown several hundred metres to the east. A 60 foot steel-trussed light tower also bent over at the base, and a roof ripped off one home and slammed into an exterior wall of the next, injuring a woman who was lying in bed at the time (dislocated shoulder). Most impressively was the 2x6 chunk of roof trussing that impaled a home two doors down, protruding into the living room.
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| The home with the roof ripped off. |
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| 60 foot metal-trussed tower tipped over |
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| Large grain bins (empty at this time of year) take flight to the east, just west of Eston. |
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| Hail up to the size of golf balls stripped homes of vinyl siding. One home had damage almost right up to the eaves despite having a large overhang, suggesting the hail was coming in almost sideways. |
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| An embedded 2x6. This image sticks with me! |
Here is a
link to a story I did on this event.
Carmangay, AB - July 18
Vulcan County has been a lot more active this year than in recent times. For a storm chaser, it is a dream to chase here owing to a decent road network amid rolling terrain, pristine cropland, and excellent visibility. This tornado (like Pine Lake, Three Hills, Jenner 2017, etc) occurred along a boundary in a classic Alberta tornado environment. These kinds of days often don't scream tornado in the days leading up to it, as they are usually post-frontal setups on the cold side of a trough, with messy low level shear profiles and less instability than before the trough came through. However, there is often usually enough residual moisture pooling into the north side of the QS boundary/front, which is impinged by strong, dry W/SW flow across southern Alberta - which can feature an impressive moisture gradient along with a wind shift and associated convergence that supports thunderstorm initiation. Ample instability results on the cool side of the boundary for severe storms amid deep layer shear favourable for updraft rotation (despite the messy low level shear profile) along the cyclonic shear side of the jet, which can support low-topped supercells with storm motions along the front, providing a steady stream of streamwise vorticity for strong low level mesocyclones. The probability of tornadogenesis may also increase in this environment owing to the presence of plentiful environmental low level vertical vorticity along the wind shift line.
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| Tornado occurred between 515-530PM MDT. Notice the wind shift, the strong moisture gradient, and the deviant motion to the SE of the parent tornado thunderstorm when updraft rotation was strongest. |
Visible satellite and radar trends indicate that the storm itself developed rapidly, as an outflow boundary from a decaying storm to the north collided with the in situ boundary.
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| Meteorogram for a nearby ag station reveal the strong, dry westerly flow that preceded the storm. |
The tornado spun up about 17km east of Carmangay in a field just NW of a residence that would become heavily impacted by it - particularly on the northern edge of the property. The home itself sustained some damage, including broken windows, impaling of branches into the home, and some stripped siding and roofing material along with extensive tree damage in the yard. Just north of the home, a well-constructed shop building was destroyed, with a car jack stand inside shifting 10 feet. Anchor bolts were ripped out of the concrete cribbing, and heavy equipment was tossed into the field - including a bale stacker that was thrown 200 metres. At the time of writing, the tornado was given a preliminary rating of EF1 - however, once again in my opinion, some of the damage (that may lack damage indicators for surveyors) suggests EF2 intensity (180-220km/h), and had an estimated (by me) track of over 10km to the SE. A couch cushion was found laying in a field of flattened peas almost 4 kilometres SE, with insulation observed almost 10 kilometres SE. The tornado would thread the needle through wind turbines at the same time that straight-line wind damage was being reported a few kilometres to the west.
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| An overview of the property impacted by the tornado. |
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| Branches impaled into the side of a home, likely from a tree bough being forcefully thrown at it. |
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| The branch coming into the living room. |
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| The destroyed shop. |
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| Damage that occurred to a barn at the Carmangay Colony to the west. |
The most memorable piece to this story for us however, was the seemingly miraculous survival of some of the animals on the property. As we were doing the survey, we heard something crying from beneath the heap of rubble that had been the shop. We looked inside, and found that it was a tiny Calico kitten. After some careful maneuvers, we were able to retrieve it from the rubble and return it to his owner - a happy little boy. Apparently there had been two, but until that point only one had been accounted for, and all hope for the second was lost.
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| Here is "Calico" - who may have used up one of her nine lives. |
The family dog Belle was also seen clawing at the ground outside the basement window as she attempted to avoid getting carried away by the tornado - but to no avail. She got carried away, but somehow returned a while later.
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| Belle standing near the wreckage of the shop. |
And finally, as we were calculating the distance that the bale stacker was thrown, a little calf came running up behind us crying. Apparently, four calves on the property had their bottle feeder destroyed near the shop, and were looking for food.
Here is a
link to the kitten rescue, is a
link to more of what happened on the property, and here is a
link to video of the tornado shot by Sara Banman - the neighbour immediately to the south. She ran for cover after finishing filming.
