August 20th, 2018 Ottawa, IL Likely Brief Tornado

Tornadoes: 1

Highest Wind Gust: ~50 mph

Largest Hail: N/A

School had just started back up, and I knew August 20th looked like a potential chase day locally. However, I had things to take care of at the beginning of the semester that would probably ruin my chances for being able to chase. I scheduled a mandatory preliminary fitness test for a single-credit PE class the previous week for this Monday at 3pm, meaning that storms likely would be well underway by the time I got out. I kept aware of the potential for a sleeper tornado event while still fulfilling my obligations back at the college.

The setup this day was generally marginal but held some conditional potential. Biggest question was destabilization to begin with, but as the setup drew near, the low was progged to weaken even more than it already was, killing much of the low level shear. Still, lots of ambient vorticity would be present in the vicinity of the warm front ahead of the occluding low, with modest destabilization seeming likely. Low level instability was also supposed to be on the favorable side. Combined with the ample vorticity, low topped supercells were a possibility:

In response, SPC put out a secondary 2% tor prob area north of the primary threat area in the South:

I technically got out of class at 11 (should've been 1, but professor never showed), but with my fitness test at 3 o'clock, I had 4 hours to blow in the meantime. I spent much of that time looking over weather data. While sitting at one of the college computers, I noticed the guy sitting next to me would occasionally glance at my screen with mesoanalysis open. Eventually, as one of my high school classmates came over to ask about the storm situation later in the day, he joined in the conversation. When my classmate eventually left, I asked him if he was a meteorology major, too. He confirmed, and we talked about weather, storms, and the day's (bleak) potential until he was forced to leave for class. Before that, I was pretty sure I was the only meteorology major at the small Illinois Valley Community College. It came as a pleasant surprise that there's someone else there that shares my passion.

A little before 3pm, I got dressed for my fitness test and took a final glance at radar, which showed a broken, marginal line of disorganized cells moving at the campus. The testing was supposed to take an hour, and the storms looked to arrive in less than half that time. If they did organize and begin to rotate, the only shot I would have would be to blast northward after them to try and catch them from behind. I didn't think anything interesting would happen, though.

The testing took only 20 minutes, which I took as a win if only for the fact I didn't have to endure another 40 minutes of it. But when I looked at radar walking out of the fitness center, I noticed one cluster of storms organized into a half-decent supercell, and was about to cross I-39 only about 5 miles to my south, near Tonica. It had only a modest couplet, but this wasn't going to be the type of day where tornadoes would drop from intense, tight velocity signatures. I raced off the IVCC campus and made for the I-39 southbound on-ramp.

After blasting through the heavy rain core, I took the Tonica exit, making my way through town to try and gain a visual on an updraft base. Rising scud started to become visible to my east as I exited the core. Of course, the storm was very rain-wrapped at the time, and road network/trees became a hindrance as I approached the Vermilion River. I noted a new cycle developing ahead of the majority of the rain as I was forced to sacrifice any visual for a little while to avoid getting trapped by the river. Driving over the river, I drove through Lowell and then Vermilionville, where I finally gained visual as trees thinned east of town. Despite marginal parameters and somewhat lackluster radar appearance, the storm had an organized, albeit a bit watery, HP structure:

The center of circulation and accompanying wall cloud was located just to my southwest and moving my direction:

There was little more than some modest rising motion at this point, but this cycle was finally getting its act together. I flipped the car around to reposition, making it another mile or two down the road before pulling over. The wall cloud had a bell-shape now, with motion increasing slightly, but not impressive. Moving once again, I pulled off, and after getting out and looking to my southwest, I noted now rapid rotation as RFD began to surge around the wall cloud. The motion was imminent-tornado-type rotation, where you're anticipating a funnel to materialize at any second:

A mini CG barrage even occurred at this point, as a massive bolt struck a quarter mile or less to my south in a field, startling me, followed by another close strike. The storm had no lightning prior to this. Rapid rotation still picking up in intensity, I stayed until the wall cloud was only a quarter mile or so down the road before bailing. Stopping yet again a minute or two later, the wall cloud was beginning to lose motion as it failed to produce a tornado. Rising motion was still very evident, though:

The circulation gradually occluded over the next several minutes as I drove towards the south side of Ottawa. I knew I was going to have to make a dash through town to keep up with the storm, as the only river crossing within a reasonable distance was there. Every time I've chased and wound up in Ottawa, it's costed me dearly on positioning. It's a big town with lots of traffic and stubborn stoplights. With this in mind, I wanted to proactively get through town so that I wouldn't lose the storm. I pulled off on a side road just south of town to find the best route, looking at radar while I was at it. Even though I was fairly close to the occluded circulation, a new one had developed on the south end of the precipitation. I looked to my southwest, and sure enough, there was a relatively well-formed wall cloud:

There was a fair amount of motion feeding into its tail from the north. I sat at the stop sign to watch it. Within only about 30 seconds or so, a further lowering developed underneath the wall cloud with visible rotation:

I was pretty certain this was a rather large funnel cloud, and its later transformation proved this to be true:

The bottom of the funnel dipped below the top of the treeline for a minute as it churned modestly. Realizing there was a car behind me now at the stop sign, I was forced to turn, opting to head back south to get into better clearing away from dense trees in the Illinois River Valley. In order to get away from the trees, I had to go through a lot more trees, though, so I lost visual for a couple minutes. As the landscape finally gave way to corn fields, I was greeted by a somewhat watery-looking but still dramatic occlusion, with the entire updraft churning counterclockwise and an elongated nub of a funnel:

Unfortunately, tall corn and a still slightly intrusive treeline blocked my view of the ground for any sign of touchdown. Given the funnel's persisting for several minutes and it being halfway (briefly further) down to the ground for most of that time, I think it's fairly safe to say there was a very weak tornado there. I feel especially confident when looking at images like this one, where the bottom of the funnel seems to be "reaching" downward (significantly contrast enhanced):

I tweeted NWS Chicago about the funnel to make sure they knew what was going on, especially given it was only a few minutes from hitting Ottawa. Given a few more minutes, it gradually dissipated, leaving only a decaying updraft tower behind. A new cycle was developing on radar right over town, and rain obscured it from my view. I had to execute my drive through town, which didn't include nearly as much hassle as the last few times. I got through in about 10 minutes, taking route 71 northeast out of town to catch up with the storm. Getting onto the back road grid, I finally caught up as another wall cloud developed just to my northeast:

I followed closely behind this wall cloud for a few minutes before rain began to wrap around and choke it off. Following through northeastern La Salle County and into Kendall County, the storm became somewhat boring. However, getting onto route 52 eastward, action started to pick up again. I found myself coming out from the rain and right underneath the updraft, as I had to look straight up to see anything:

I ran into a caravan of chasers, and someone must've recognized me, as they waved as I drove by. This turned out to be Matt Piechota who later identified himself on Twitter. Everyone was pulling over to watch what this cycle would do while I headed a bit too far east before doing the same. I couldn't get much of any visual as the RFD quickly filled in with rain:

The circulation actually tightened up an appreciable amount as it passed over Newark, and I wanted to get closer to gain a visual through all the precip. On the quickest back road to get there, I lost cell service as I got into intense RFD winds that approached severe levels. I was still getting westerlies, and the odds of a tornado actually being present were low, but without radar, I didn't want to risk putting myself in danger.

This cycle finally choked off, and of course, another one was trying to get going, this time near Lisbon. Making my way through some construction on 52, I pulled off on a back road to pull over and look. It was at this point that it became glaringly obvious the storm was probably on its way out in terms of supercell/tornadic potential (although it never had the same vigor after passing through Ottawa). With this sloppy, choking wall cloud, I called the chase and started the hour drive back home:

Overall a fairly fulfilling day. I thought I was going to have to miss whatever happened due to responsibilities, but I got my cake and was able to eat it, too. I pretty much just got lucky, as the storm closest to me just so happened to be the one to produce the most interesting weather. This was my first August tornado, and my first tornado on a solo chase. I've seen tornadoes without other chasers, but someone else was always driving. This will get to be one of my not-very-remarkable but still special days because of the circumstances that led up to it.

GPS Location History:

SPC Storm Reports: