Tornado season is only about halfway over, and Monday brought another reminder of that. Two tornados touched down only one mile apart in the small town of Pilger, Nebraska. The twin tornados left two dead and at least 16 others critically injured. 

At least one of the tornados was confirmed to have created at least EF4 damage, with winds ranging from 170-200 mph. 

Twin tornados don’t get documented very often, but they aren’t believed to be extremely rare. Storm systems with as many as five vortices have been documented. Following the storm, meteorologists have explained that multiple-vortex storms typically have vortices that are harder to see, making Monday’s storm quite exceptional in its own regard. 

There are a few different ways that multiple-vortex systems could arise. Some believe that the second funnel split from the first. This could be a fairly common occurrence, though the secondary vortex is likely much smaller. 

For double tornados made from occlusion, one funnel gets wrapped up in colder air, causing it to dissipate. The system, however, still has enough energy to create another funnel. This is the most likely cause for double tornados; it was just rare to have funnels on the ground simultaneously. 

Another explanation is that the tornados are actually completely unrelated and just happened to occur right next to each other. Though storm systems typically aren’t in such close proximity with one another, this is still a possibility.

Check out the damage caused by the twisters here: 

MAJOR damage here in Pilger, Nebraska need emergency personnel NOW!! pic.twitter.com/rF6SpxBd36

— Reed Timmer (@reedtimmerTVN) June 16, 2014

Pilger, NE #Tornado Before & After from @Bmendlik & @Google Streetview pic.twitter.com/POteMMcBZT

— EricSorensen (@ERICSORENSEN) June 17, 2014

[Hat tip: Bill Chappell, NPR]