Warm front play in central Illinois. Targeted developing supercells near Carrollton, IL before updraft and wall cloud caught my attention near Waverly. Noted low contrast, weak tornado at close range north of Waverly. Chased remnants of Divernon tornado circulation and parent supercell all the way to Decatur before calling the chase near Clinton.
Crew and Equipment
Solo chase. Equipment: Sony AX100, Samsung Galaxy S9.
Video
Map
Details
I opted for a play closer to the warm front on and north of 72 rather than the 3Cape bullseye over St. Louie that baited a lot of chasers south. Enroute to a discrete, developing cell over Carrollton, I noted that the cell north was sporting a very attractive base. It looked like junk on the radar though, just a weak, disorganized cluster. The situation reminded me of 19 April 2011, on which Brindley and I were making for Tail End Charlie, just a few miles away from this same location in Illinois, when I spotted a base on the middle cell in the line and thought, "That looks great. I'd chase that." We had our closest encounter to a strong tornado a few minutes later. I know better than to drive away from great structure in favor of radar presentations, so I stayed on the north cell.
A block wall cloud soon developed, a tail cloud was added, and then the wall was cleaved into two lobes.
The structure reminded me very much of our 21 May 2011 White Cloud, KS intercept on which we got a weak tornado several minutes later.
There was a tornado watch, but the cell was yet unwarned.
An RFD clear slot developed out of the updraft base (right). Meanwhile, the rainy forward flank of a cell to the south was encroaching and cutting off my view (left). I had to make a decision: abandon the cell and find a new target, or push into the rain and under the clear slot for a close intercept on the current cell.
The cell was exhibiting a textbook wrap-up to tornadogenesis, and I didn't want to give it up just as it was going to produce. I decided to push inside for the close intercept. I lost my visual almost entirely in the warm summer rain, but as I stair stepped on the small, rural roads, I could make out a dark shape looming over the corn. I turned the car south to face it. Contrast was incredibly low but I could see a shaggy, ground scraping lowering with motion underneath as streaky rain bands spiraled around it. I had seen this before too. It was a developing tornado. Contrast enhanced video clearly shows suction vortices flicking up beneath the parent lowering.
Our local Skywarn net had been activated, but I was out of range of the repeater with my little 5 watt handheld. I instead texted net control to relay a report of a developing tornado to the Lincoln, IL NWS forecast office.
In the following minutes, I only had a vague visual on the likely tornado as a dark mass in the rain. Radar reflectivity looked weak and sloppy, but you could make out the spiraling pattern of a supercell cycle and occlusion. Velocity was another story, which showed a distinct couplet even on the lower resolution level 3 scans. I was gawking at it, expecting a big tornado warning polygon to pop up any second. No tornado warning appeared, however.
I had the window down trying to strain my eyes for contrast. The air in the near tornado environment was incredibly warm. It felt like it was in the 80s, warmer than the environmental warm sector outside the storm even. That might just be my human tendency to exaggerate, but it reminded me of a heat burst. Maybe an occlusion downdraft that was warmed by mechanical forcing.
I nosed in eastward hoping to establish a better visual. The dark lowering could be seen coming in over the tops of the trees to my south.
And then I was suddenly too close. Leaves and small branches started to loft into the air followed by a jet of strong southerlies blasting the plant debris across the road. Trees on my right, powerline lines on my left, I was worried something might come down on me. I put the car in reverse and backed up until I was clear of the treeline. The winds had largely subsided by then.
Small branches were down in the road. A nearby farmstead looked completely undamaged though. I was able to hit the Springfield repeater and checked into Skywarn net control with a tornado report, giving the exact location where it crossed this time. The tornado appeared to have dissipated but I made out a bowl lowering as it moved off to the north.
I pursued the storm north. It never received a warning of any kind. A large white funnel cloud appeared to be roping out (shown here heavily contrast enhanced), but I could barely make out the right edge through the murk before it disappeared entirely. The storm rapidly dissipated as it crossed north of 72. I stopped in New Berlin to verify times and locations of the tornado over the radio. The Lincoln office wasn't convinced by the reports or the radar. The stop cost me minutes, and probably a view of the Divernon tornado that was about to develop.
A small supercell approaching Divernon was tornado warned and already had spotter reports of a rain wrapped tornado on it. The warning was allowed to expire just as a much more robust looking tornado developed. I scrambled east to get ahead of the storm, turning south before Pawnee. I heard reports of it over the radio, and could see more coming in on Spotter Network. Over the tops of the corn and through the misty haze I could see a dark lowering churning beneath the mesocyclone. I was convinced I was looking at the Divernon tornado.
But the tornado had likely just ended and I was a few minutes late to the show. Turning west with an unobstructed view, I could see a dramatic cylindrical lowering, but it wasn't in contact with the ground anymore.
I chased the cell all the way to Decatur. It cycled a few more times with some eye catching structure, but was shrinking and becoming more elevated each time as it tracked into cooler air. I then made an excursion up to Clinton to give some additional cells a shot, but the day was winding down.
I called it and headed for home. Some low contrast mammatus was visible, followed by gorgeous purple and pink rows of cumulus in sunset light.
Conclusion
One of my few tornado intercepts of the 2020 season, this was a dramatic, close range encounter just a few miles from home. And yet the lack of acknowledgement of my reports, and that I needed three different shots to justify the weak tornado, made me feel like I was crying wolf. The initial subvortex shot showed a clear connection to the ground, but not necessarily that violent winds were present. The blast of debris crossing the road established the damaging winds, but it was the partially condensed, roping out funnel cloud shot that tied all of this together as a tornado, albeit a brief, weak one. The Weather Service did go on to log it as an EF0 tornado based on my reports after following up with me after the event. The Divernon tornado was the catch of the day, however, and I was a bit bummed I missed it. It looked pretty significant, but wound up being rated EF0 as well. I suspected that the warm temps at the surface might have kept low level buoyancy high, but took some of the bite out of the surface winds and downdrafts needed to spin-up stronger tornadoes.
Lessons Learned
Don't waste time validating reports mid-chase. Just make the report, carry on, and then follow up after the chase.
