Rare twin tornadoes plowed through the small town of Pilger (population 380) in northeastern Nebraska Monday night, killing at least two people. According to the National Weather Service in Omaha
, these were the first tornado deaths in Nebraska in over ten years, since the May 22, 2004 Hallam, Nebraska tornado. Yesterday's unusual twin tornadoes were part of a tornado outbreak that brought nineteen tornadoes to Nebraska and Iowa that injured at least nineteen people. According to Sheriff Mike Unger of the Stanton County Sheriff's office, 75% of Pilger was destroyed, including 100% of the business district. The church, school, and fire department buildings were demolished. NWS damage survey results from Tuesday showed several spots of EF-4 damage in Pilger.Figure 1.
Picture from Reed TImmer (@reedtimmerTVN) of twin tornadoes and severe damage near Pilger, NE #newx on June 16, 2014.Figure 2.
The twin tornadoes that devastated Pilger, NE on June 16, 2014. Image credit: Greg Johnson.Figure 3.
Radar reflectivity image of the powerful isolated supercell thunderstorm that hit Pilger, Nebraska on June 16, 2014.Figure 4.
Doppler velocity image of the Pilger, Nebraska supercell thunderstorm on June 16, 2014. Two separate areas of spin are apparent on the radar, with winds blowing towards the radar and away. Pilger is marked by the circle with a "+" in it.Video 1.
Rare twin tornadoes near Pilger and Wisner, Nebraska as caught by iowachase.com
(AKA StormChasingVideo.com.)Video 2.
Rare twin tornadoes near Pilger and Wisner, Nebraska as caught by BaseHuntersChasingVideo 3.
Aerial damage survey from a Nebraska State Patrol helicopter shows the damage swath through Pilger, Nebraska, on June 16, 2014. Damage was as high as EF-4.Twin tornadoes are rare
While it is common for large, violent tornadoes to form multiple funnels that rotate around each other, Monday night's Pilger, Nebraska twin tornadoes were not one of these standard "multi-vortex" entities. The Pilger tornadoes were separated by 2 - 3 miles, and were both spawned by the same isolated supercell thunderstorm. A rotating supercell thunderstorm typically has just one center of rotation and spawns only one tornado, but Monday's storm was so massive that it was able to form two centers of rotation that each spawned large and destructive tornadoes. Video taken by iowachase.com
shows a large tornado hurling debris into the air near the 3:31 mark, and by 3:32 a second tornado touches down 2 - 3 miles away. Within minutes, the 2nd tornado grows very large and puts a substantial amount of debris into the air. Figure 5.
The most famous case of twin tornadoes occurred on April 11, 1965, during the notorious Palm Sunday Tornado Outbreak.
These twin tornadoes that hit Elkhart County, Indiana caused F-4 damage and killed 14 people. Just 45 minutes later, a second F-4 double funnel
hit just two-and-a-half miles away, killing 36 people. The twin tornadoes in this image were probably not two separate tornadoes, but rather one multi-vortex tornado with two impressively large funnels. Here is a paper by Fujita et al. on the 1965 Palm Sunday outbreak, including a detailed analysis of the twin tornadoes in the photograph: http://docs.lib.noaa.gov/rescue/mwr/098/mwr-098-01-0029.pdf
. Unlike the Pilger twin tornadoes, the 1965 twin was a single tornado which broke down into two circulations. Image credit: Paul Huffman
Thanks go to wunderground members Sfloridacat5, Ameister12, Doppler22 and barbamz for posting some of the links used in this post.