June 22, 2016

Only home for a couple days after over three straight weeks on the Plains, the weather was setting up for a potentially significant tornado event. Fortunately it was much closer to home this time. A warm front was forecast to lift northward through northern Illinois beneath strong northwest flow aloft.

It was remarkable that a very similar setup occurred a year earlier to the date and over the same locations. The combination of moderate to strong instability, low LCLs, and strong helicity along and north of the warm front was causing the tornado parameters to spike. The wildcard was the morning storm activity, which would dictate whether the event featured discrete supercells with a tornado potential or an MCS with damaging winds. Some form of severe weather looked likely with the potent ingredients coming together, however. Illinois warm fronts can be magical, but they often don’t come together until the last minute, the ingredients for tornadoes materializing immediately ahead of the developing storms as the warm front lifts. Instead the target area looks rather bleak most of the day, under cloudy or rainy skies. This causes me to get suckered westward into Iowa, where the sun is out and the atmosphere is destabilizing only to see tornadic supercells go up a couple hours later at my original target area while I’m hopelessly out of position. I had been burned several times in the past because of this, including on last year’s chase. Our last chase with team TIV and we got suckered into Iowa as Illinois finally lit up with a tornado outbreak at dusk. I was determined to hold my ground this time, and even setup downstream so I wouldn’t get baited too far west chasing the early ongoing junk. I set an initial target of Rockford, IL.

I still hadn’t returned the F-150 I rented in Montana after the van died in Great Falls. I decided to take it on one last chase before returning it in Springfield. Brindley and I teamed up for this chase, rendezvousing south of Rockford where we also bumped into friends and Indiana based storm chasers Joseph Cooper and Beth Carpenter. A morning MCS was ongoing, pushing off into Indiana, but ongoing storms were redeveloping in its wake and on the effective warm front to the northwest. We held our ground, not wanting to get baited away from our target, and waited for something more discrete.

A line of storms encroached our position from the northwest so we started to drop south. Multiple cells were now organizing into embedded supercells within the line due to the excessive directional shear. We kept ahead of the line waiting for something dominant on which we could make a play. A cell just to our north picked up a tornado warning and we moved in for the intercept. It was embedded and high precipitation, but a lengthy rear flank downdraft gust front came into view from the west. The cloud to ground lightning was intense and prolific. A barrage of bolts cascaded around us, often a precursor to tornadogenesis. The apex of the bowing gust front looked like it was going to pass to our south, so I actually maneuvered us north for safety reasons and as a preemptive escape route. That’s when we spotted the tornado, further north than I expected, but the gust front was lengthy and we had finally found the northern end that curled back into the supercell’s updraft. “There’s a tornado” Brindley called out. A low contrast stovepipe loomed in the distance, grey on grey, above the corn. We could just make it out.

I continued north up to an intersection, but our view of the tornado did not last long. It quickly became completely wrapped in rain and disappeared from sight. The tornado tracked just north of Compton, IL and was rated EF1. The storm was still marching east southeast on our position, the bowing gust front already ahead of us to our south as we were caught in the inflow notch. The storm overtaking us, and with no view of the rain wrapped tornado, we’d still have to take our escape route. I went east southeast at the intersection and hopped on 39 south, hoping to get ahead of the storm’s gust front. The bulk of it had already crossed the highway, however, and knowing better than to punch the Bear’s Cage on an HP supercell we pulled a u-turn on the highway and went back north. We waited in the storm’s forward flank precipitation core until the radar showed that it had cleared the highway. There was no hail, only heavy rain. A couple of supercells were trailing to the southwest. Once clear of our original storm's hook, we dropped south to head off the next tornado warned storm in the line as it crossed the highway.

Near Troy Grove we were greeted by the huge meso of a high precipitation supercell. We stopped ahead of the storm, and waited for it, hoping visibility under the base would improve.

Another intense cloud to ground lightning barrage began, and I thought for sure the storm was gearing up to produce another tornado.

An amazing cascade of bolts struck all around us. Cloud to ground strikes within a couple miles were hitting at a rate of several per minute. My ears were ringing from the thunder. Antennas down the road, the interstate, and what looked like a tree momentarily erupting in flame were being hit. I had never seen such an intense CG barrage in my years as a chaser. We made sure our hands were off the truck’s frame and put our electronics down to minimize our chances of being electrocuted. Then we just sat and waited for the storm to approach and the lightning to hopefully subside.

The storm exhibited prominent midlevel rotation and was getting pretty close yet we still had almost no visibility under the base.

We ran east and south to keep ahead of the storm and try to improve our view. The storm’s low base and green core looked ominous. Buried within the rear flank core was a suspicious looking dark column.

A bright power flash momentarily illuminated the storm from the ground, likely caused by a rain wrapped tornado. I suspected it might be a large one too, given the incredible CG barrage that preceded it, the impressive parameters in play, and the size of the dark column we saw within the core.

Moments later another power flash appeared as the tornado continued to track along west of the interstate. We didn’t have visibility on the funnel, but the power flashes and position coincided with an EF1 surveyed by the weather service. Chasers playing inside the Bear’s Cage had a momentary shot of a snaky rope tornado before it became rain wrapped.

The storm approached with dramatic structure, a menacingly dark base, inflow tail streaming off to the northeast and a turquoise core. Tendrils of rapidly rising scud started to condense beneath the base of the tail cloud and I thought we’d soon have another tornado. The activity soon subsided though.

We ran east to stay ahead of the storm, winding up a few miles north of Ottawa, IL. The CG show continued. Despite the storm’s high preicipitation nature, we had decent visibility on structure within the base. The rear flank downdraft gust front curled back into the storm where a suspicious bowl lowering was located, an inflow band streamed in from the northeast. I shot the base through the window waiting for what looked like textbook structure for tornadogenesis.

Light was fading fast as the sun had set and all that was left was a sepia toned twilight beneath the base. Motion under the bowl lowering was rapid, rain curtains and scud careening around in a circle. I suspected a tornado was in progress but it was difficult to confirm in the low light and without a strongly contrasted funnel. The weather service surveyed another EF1 at the location, our third tornado intercept of the chase. Night fell by the time we were moving east again and multiple cells were congealing into an MCS. Despite ongoing tornado warnings, we decided to call the chase. We ducked south of the complex then west to get behind it, and finally north to get Brindley back to her car in Rockford.

I stopped and shot some time lapse lightning on the way home. Storms were low topped by then with mostly cloud to cloud flashes, and my view was soon cut off by low cloud cover. It was still a pretty yet eerie display, however.