The evening of Friday, June 9 turned out to be a very exciting and destructive time as severe thunderstorms blew their way through Cavalier County.
By Melissa Anderson
Greg Gust, Warning Coordination Meteorologist at the National Weather Service in Grand Forks, released a preliminary storm report for the June 9 event listing two short 1-2 mile long tornado tracks and one substantially longer tornado track. The first tornado was around three miles east of Wales and was identified with assistance from Cavalier County Emergency Manager Karen Kempert. This tornado was rated an EF0 with wind speeds between 65 to 85 mph.
The other shorter tornado was around 3 miles north of Langdon, and was rated an EF1 with wind speeds between 86 to 110 mph. The last and longest tornado was roughly 20 miles long and extended from 8 miles east-southeast of Langdon down to about three miles south of Mountain. This last tornado was rated an EF2 which has wind speeds of 111 to 135 mph.
“The first two were a bit more distinct while the long third one was a real bear,” Gust shared. “I suspect it was much like last year’s long-tracking Bisbee Tornado which occurred on Aug. 3, 2016. It was nearly as wide with the tornado engulfed at times in the down burst winds and hail. All of these contributed to the huge amount of ground/crop scouring which occurred over such a broad area.”
There was a number of discrete hail or wind damage reports and a number of more broadly described impact areas, with wind-driven hail and extreme winds scoured crops and mowed down trees across a wide area.
For Cavalier County, this describes a 6 to 12 mile wide band across the prairie that had extreme damage as a result of strong winds.
“That’s 6 to 12 miles wide of 60 to 80 mph, at times even 80 to 100 mph. Within that, there was likely a much narrower band of the tornadic winds from 200 to 600 yards,” Gust said.
This band extends from between Sarles and Hannah point of entries at the north border, towards the east-southeast between Langdon and Olga, continuing on between Hoople and Hensel, and between Grafton and Drayton into and across the Minnesota border.
“The extreme winds and hail from this particular supercell had begun at least as far northwest as Clearwater, Manitoba, Canada and continued on past Newfolden, Minn.,” Gust stated.
The intensity of the June 9 storm can be contributed to a combination of four factors that, when occurring at the same time, create storms known as supercells. All thunderstorms require three ingredients to form: moisture, instability, and lift. Supercells, on the other hand, require all three of those plus an additional factor – wind shear.
A supercell is a thunderstorm with a deep, persistently rotating updraft. Supercells are the least common form of thunderstorm yet they are potentially the most violent. Supercells are made up of several different parts. At the most basic level, a supercell features a deep, rotating updraft and a strong downdraft. An updraft is where warm and moist air rises and condenses within the storm and, thanks to strong wind shear, the updraft and the downdraft are typically in different places — which allows the storm to thrive as it can ‘breathe’.
Underneath the updraft at its strongest point is oftentimes a wall cloud. A persistent and rotating wall cloud indicates the potential for tornado formation and should always be watched closely. Supercell storms have three classifications: Classic, HP, and LP.
“I believe this one started as a more Classic Supercell and evolved to a more HP (Heavy Precipitation) one as it moved across the area,” Gust said.
“A Classic will typically have the tornado more detached and trailing behind the heavy rain and hail corridor, while the HP will have heavier rain, hail, and wind at the lead of the storm along with a band of rain and hail wrapping around the back of the tornado itself,” Gust added.
While the weather conditions created a perfect set up for the supercell to form, the topography of Cavalier County also assisted in the storm dealing such heavy damage to areas. The topography played some role in that the more narrow draws and coulees along the escarpment would provide some protection where winds would not penetrate quite as easily.
“Both tornadoes and down burst winds have a main component of horizontally driving air. The friction layer near the ground helps to slow that wind down somewhat,” Gust said.
The rougher or higher relief the surface has, the less wind penetration occurs. So in the forested area there can be tree-tops snapped off by the wind and yet there is hardly any sign of the storm on the ground.
“A more wide-opened crop land or lake provides almost no impediment to the wind and thus, we will see the higher level down burst and tornadic winds drive down much closer to the dirt or water level – often leaving ground scars and peeling crops away,” Gust said.
Several residents in Cavalier County experienced first-hand the destructive force that a supercell can have on property. Their stories and photos from the aftermath can be found in this weeks issue of the Cavalier County Republican, available on newstands now.