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Twin tornadoes three days in a row

Amazing and destructive tornadoes in Nebraska and South Dakota.
Amazing and destructive tornadoes in Nebraska and South Dakota.
Tim Marshall - Radar Scope base velocity comparisons

There was a series of tornadoes occurring June 16th , 17th, and 18th of 2014, that spawned a number of powerful and deadly tornadoes. Most notably where twin powerful tornadoes, one of which struck the town of Pilger, Nebraska, killing two people and critically injuring dozens (See main picture). Another strong tornado hit Wessington Springs, South Dakota on June 18th, and fortunately due to early warning systems, and possibly less intensity, the tornado only injured two people.

Basehunters storm track team identifies and reports large threatening tornadoes
Basehunter's Chasing, Scott Peak

What made all three days, the 16th, 17th, and 18th somewhat remarkable is that twin tornadoes occurred within the same supercell storm, nearby, on all three days! (See comparable Radar Scope velocity scans, Courtesy: Tim Marshall) The twin tornadoes on June 16th were the most remarkable of the three days, as they were both very strong tornadoes for a period of time. A number of people have pointed out that multiple tornadoes occurring, in the same cyclic supercell can be fairly common, as the older occluded tornado reaches the end of a lifecycle, and a new tornado forms, yet the environments over the last couple of days have been so primed that multiple tornadoes have coexisted at significant strength.

A cyclonic pair and tornado merger, named the Fujiwhara effect (Named after Dr. Ted Fujita) is presumed by a number of atmospheric scientists to be responsible for these co-existing tornadoes and their mergers. However, there is some technical debate about Fujiwhara as most complementing rotations have clockwise and counter clockwise rotations, and both these tornadoes were cyclonic, not anticyclonic. However, both cyclonic rotations seemed to rotate around a center mass somewhere between each tornado.

Multiple tornadoes are not uncommon in such powerful supercells, as a parent wedge tornado may often have smaller rope or stove pipe tornadoes pulled around the main tornado circulation, and these are referred to as satellite tornadoes. “I personally witnessed this on the Bowdle EF4 tornado,” comments one tornado tracker. Also, it is common for a cyclic supercell to spawn multiple tornadoes along the course of the storm, yet more often, an older tornado rotation will get choked off by rain cooled air before a new tornado will form, but not always, as the last several days have demonstrated.

What is a bit more uncommon is for multiple wedge-like tornadoes to be present at the same time in the same supercell storm, and at such high intensity, as was present on June 16th, 2014 in Pilger, Nebraska (See main picture, courtesy of Basehunter’s Chasing and Scott Peake).

Certified and trained storm trackers can form an important link in the communication chain when multiple tornadoes, or multi-vortex tornadoes occur at the same time, as Doppler, even Dual Doppler scans at a considerable distance cannot always predict the exact location of multiple co-located tornadoes. Time is of the essence in early warnings and threat detection, when such storms approach populated areas.

Simultaneous tornadoes can also pose a significant hazard to storm trackers, first responders, and law enforcement, as it becomes easier to be blind sided by a second tornado, especially when a large tornado is on the ground, and is the most dominant focus of attention. Reed Timmer, veteran extreme storm chaser said, “in a cyclic supercell, you always have to watch your back, because an old occluded tornado can still be there, on the ground and deadly, and more likely rain wrapped when a new powerful tornado cycles into view.” It is usually the one you cannot or don’t see that can get you.

Possibly a day will come when storm spotters (needed to ground truth actual tornadoes) are not necessary, with advances in meteorological technology, and when gaps in Doppler scanning fields are filled, but that day is likely many years in the future. Presently, first responders; such as police and fire rescue units do not have onboard computers to scan local storm environments for such emerging threats, are not trained to use such equipment, and are focused on other critical missions. There are minutes of delay from communication through Dual Doppler scans and transferring such information into the field to first responders, and rapid emergence of powerful tornadoes (such as the Joplin EF5 that occurred in less than a minute, and became a milewide, after becoming surface-based).

For professional storm spotters, the task of being situationally aware in every direction is difficult, but a matter of self preservation, and such seasoned wisdom is the ability to accurately and rapidly identify emerging threats to communities, and have the ability to communicate those threats to authorities in time, while staying safe.

One professional storm spotter warns onlookers, “If you see my intercept vehicle in a dangerous storm, don’t follow me.”