However, the National Weather Service in Topeka today released an addendum to their original survey identifying and adding a new tornado (EF2) that was previously unreported in southwest Douglas County, Kansas. This was the rain-wrapped tornado that struck SLT, rolling two of their vans, and was located at the time of the incident within the rain-filled rear flank downdraft (RFD) of the developing mesocyclone to its north that gave birth to the large Lawrence-Linwood tornado.
As I suggested in my prior post, this additional tornado was not a satellite tornado, but a separate tornado that had not yet been confirmed or reported previously. It ended up merging with the developing large Lawrence-Linwood tornado, a complex and fascinating evolution and interaction.
Here's a map I constructed by putting together NWS Topeka and NWS Kansas City survey maps of the two tornadoes. This shows the full tracks (nearly 43 miles total) and where the two tornadoes merged:
Roger Hill was kind enough to share his video with me privately, shot while SLT was retreating to the south away from the developing Lawrence-Linwood mesocyclone and what they thought was away from danger. With Roger's permission, here's a panoramic image I put together from his video as they were pulling away to move south:
You can clearly see the visual mesocyclone to their west-northwest (at right), also the focus of several other chaser videos online. But also notice the advancing rain-filled RFD coming up from their south (center of the image) that unbeknownst to them contained a hidden and unreported tornado that no one yet knew about.
Most spotters and chasers are taught to stay southeast of northeastward-moving mesocyclones (areas of organized rotation in supercell storms) to stay safe. So, SLT thought they were doing the careful thing to head back south to Highway 56 and follow the primary mesocyclone from a safe distance.
Complaints and accusations online (Facebook, Storm Track, etc.) have focused on the question, "What was SLT even doing in the bear's cage?" Well, that question kind of misses the point when the room becomes dark and you don't even know an additional bear's cage is there after you're already steering clear of the main bear's cage that you know is behind you.
The tornado merger in this case was very similar to the Hesston-Goessel, Kansas tornado merger I studied on March 13, 1990 that led to an EF5 tornado:
The difference is that the 5/28/19 merger took place hidden in rain within an HP storm, while the Hesston-Goessel supercell was a classic non-HP storm and very visible. In fact, we might not have even known about this merger had SLT not had their encounter!
To my knowledge, this is the first time a merger of two separate medium or long track tornadoes has actually been documented within an HP supercell, although similar mergers have undoubtedly occurred but not been documented. This case certainly deserves further study from several perspectives.
Thanks to meteorologist and severe storms expert Greg Stumpf for being astute enough to recognize the similarity to the 1990 Hesston-Goessel merger/interaction, and mentioning it on Facebook already several days ago.
- Jon Davies 6/5/19