Crossing the Line - Gillett, WI Tornado

On the afternoon of Monday, July 6 2015 storm chaser's Chris Valley and I set out for northeast Wisconsin.  Over the last four years we had success storm chasing on our own adventures but Chris and I hadn't had much luck chasing the upper Mississippi Valley region together. We joked about how Wisconsin-like it would be if we broke the curse today. We agreed that expectations were just about as low as they could be for a storm chase.

I felt a full explanation was necessary due to the complicated nature of event's that afternoon. This story is dedicated to our experiences on Monday July 6.

Getting in Position

WIND & MSLP at 4PM
WIND & MSLP at 4PM

Rain and clouds cast doubt over the potential for severe thunderstorms Monday afternoon. By noon we knew severe weather would be unlikely because the atmosphere just wasn't going to destabilize enough, but the tornado threat continued. Our lunch update explicitly mentioned the potential for tornadoes with little/no threat for severe weather otherwise, something we had never done or seen before. Prior to July 6 2015, six of the seven Wisconsin tornadoes this season were not tornado warned. We saw the stars aligning again and I was concerned history would repeat itself.

That afternoon I had been watching a cluster of storms near Steven's Point, WI. My confidence was high based on short range model solutions and real-time analysis. All I was waiting for was an updraft to become established on the southern edge of that complex before committing.  A storm updraft finally became established and immediately caught my attention. I knew the window of opportunity would be small but getting to Clintonville ahead of the storm would also be too tight, so I decided to try a route further east with intention to work back west eventually. I left Oshkosh targeting the Shawano area at 3:30PM.

Lack-luster radar returns. No lightning or hail was observed during our chase.
Lack-luster radar returns. No lightning or hail was observed during our chase.

I joined Chris in Appleton shortly after 4PM. We agreed on the plan and went north on HWY 47 towards the Shawano area. From this point forward Chris took control of navigation/radar interpretation, I focused on driving, and we shared in decision making. Chris pointed out that a tiny, new cell had developed on the southern side of the main one now moving into Marion. If the main cell got undercut or cut off we would target that instead.

We drove north until HWY 29 south of Bonduel and found a country road to pull off onto and wait. Despite weak reflectivity returns, no lightning, and an otherwise lack-luster visual appearance; the updraft had been showing intensifying rotation, a distinct reflectivity figure, and right-movement for several scans peaking southwest of Marion. I assumed a tornado had touched down near Marion and we had missed the window. I was simply hoping the storm would hold together long enough for us to actually see it.  Then unsurprisingly the tornado warning was issued.

The Intercept

With our forecast verified, all that was left to do was chase the storm and try to learn something. We left our hill on the east side of Bonduel and started west on a country road adjacent to HWY 29. It was raining quite heavily as we moved west to intercept the storm.

Shared via the National Weather Service -  Two circulation. What we refer to as one storm in the title was actually two.
Shared via the National Weather Service - Two circulations. What we refer to as one storm in the title was really two.

The western cell which produced the Marion EF1 and Pella EF0 tornadoes peaked and began to weaken. Chris pointed out that the cell closest to us directly south of Shawano was likely to become dominant and I agreed. There was a period of time where both srv couplets existed simultaneously. We choose against the western cell because of our position and expectations.

Rotating wall cloud southeast of Shawano
Rotating wall cloud southeast of Shawano

The haziness made it difficult to get a view of the storm. We didn't get a visual on the wall cloud until we were only a few miles away. We crossed over HWY 29 on highway K stopping just on the southern side of the highway. Because we were in the direct path of the circulation we would NEED to move eventually and HWY 29 would be our eastern escape route. The structure was not impressive but the wall cloud was quite obvious. It appeared like an eddy along an outflow boundary. All things considered, I assumed it was rotating on first impression but it took a few minutes before we could confirm that.  As the wall cloud pushed within a couple miles to our southwest it at the very least maintained it's structure. The wall cloud got too close for comfort, so I set the camera down to shift into drive and get on the off ramp.

Chris entered the vehicle and as that happened, we both noticed(or watched) a wispy condensation vortex or stringer emerge from the tree tops and extended a few hundred feet high on a forested hill one mile ahead of us. I didn't stop to think/decide whether it was debris or scud. Having seen this happen on chase in June I immediately suggested Chris call it in as possible tornado touch down.  It happened for maybe 10 seconds, then we moved.  The damage survey did not turn up anything which leads me to believe it was likely fast moving tree top condensation and not debris or tornado but I would handle things the same way in hindsight.

 

Possible rain obscured wall cloud in the distance. Looking north along HWY 22 southeast of Gillett
Possible rain obscured wall cloud in the distance. Looking north along HWY 22 southeast of Gillett

We got back on the highway we lost sight of the storm as we headed back east towards Bonduel. In our short time with the storm, I perceived the storm to have peaked and expected it to collapse soon; it did not collapse and we continued to pursue it. We started north towards Cecil with the storm on our left(west-northwest). We arrived at the T-intersection and viewed  interesting but disorganized structure. We started northeast and eventually pulled off onto a hill east of town but north of HWY 22. This part of this storm's evolution was very disorganized and it was a little unclear visually what was going on. We observed a gust-front like boundary(possibly the cold front itself) and associated shelf cloud south of the main srv couplet moving in quickly from the west. I was aware of the lowering to the northwest but watched a little bit of everything to make sure there were no surprises.

The couplet started intensifying once again but became rain wrapped. This is when it got a little weird. We stopped looking at base reflectivity opting to chase using SRV and BV instead. As we drove east attempting to get back ahead of the storm/rain everything became strangely non-descript. It was just like driving through a heavy rain shower or rain shaft, absolutely nothing to see and it was very strange.

Screen capture of our position relative the SRV couplet
Screen capture of our position relative the SRV couplet

We made the turn north on county road BB and started traveling north. Chris repeated several times that we would be near the circulation soon and we payed close attention to the radar and timing. I thought that if anything the main circulation would pass over the road in front of us judging by radar scans and anticipated delay. It was incredible how there were literally no visible clues to gauge position or speed relative to the tornadic circulation or storm itself.

This was true until we got to approximately one mile south of Gillett, WI. The rain bands began to change direction and speed, I knew we were getting close. When the winds started rushing out of the east we pulled over and seriously reevaluated the situation. When I looked to the southwest I saw several tree-top cloud condensation stringers forming and rising violently at an angle up and towards the north. As a whole, there was violent south to north (cyclonic) motion and it was approaching with a slight bowl/curved form. It was like a collar cloud but on the ground(or tree tops). We were already in the outer bands of a broad circulation; the tornado was within 100 yards and heading straight for us!

It was so alarming I went into shock. My first thought was to turn around, second thought was go north.  All I could say was "GO GO GO!"...and I was the one driving! I thought we would be okay as long as the east winds don't abruptly intensify...and they did pushing the Escape hard to the left as I accelerated. There was only one push and once we got through it we quickly pulled ahead and the winds stopped.

Power flash as the tornado crossed HWY 22 a quarter mile up ahead. Caused by tree limbs stretching the power line.
Power flash as the tornado crossed HWY 22 a quarter mile up ahead. Caused by tree limbs stretching the power line.
My illustration of what I observed 1mi south of Gillett.
My illustration of what I observed 1mi south of Gillett. Violent/rapid movement similar to what I would expect in a tornado just above tree tops.

We drove straight into Gillett and as Chris reported a tornado to the National Weather Service I tried to navigate the frustrating city roads. We emerged back onto HWY 22 just east of Gillett and starting traveling very slowly east. We were north of the tornado now and didn't want to drive back into it. We were surprised to see a couple power flashes as the EF1 tornado crossed about a quarter mile further down the road. We crossed through the debris and started looking north for any signs of rotation but all we could see was rain. The SRV couplet disappeared shortly thereafter.

Crossing the Line

As mentioned earlier, an encounter like this deserves an explanation. It was something that happened out of curiosity and desire to learn. Sometimes you need to cross the line to know where it lies. You simply cannot know unless you try.

Arrow shows heading of narrow patch of debris..possible tornado path.
From the video footage, arrow shows heading of narrow patch of debris..possible tornado path. Occurs after we drive through.

The damage survey conducted the next couple days revealed three tornadoes, two near Marion and Pella with the third on the east side of Gillett. It was slightly discouraging for us to know no damage was observed exactly where we intercepted the Gillett tornado to help justify our claims other than a 10 yard wide patch of mulched leaves/twigs.

My guess is that when we encountered the circulation it was not strong enough to do damage at the surface. The trees and forest were thick and likely acted as a perched(or false) surface.  The tornado didn't do much if any damage until it reached the open area along HWY 22 suggesting unobstructed surface winds were key. On our escape from the outer bands we actually crossed paths with the tornado. We would have been okay if we turned around or stayed where we were.

As for the possible touch down south of Shawano, that was probably only fast moving tree top condensation occurring underneath a rotating wall cloud. The storm was trying to connect with the surface and it was a sign of things to come. The storm moved then northeast and crossed over Shawano Lake, a cold body of water that likely weakened the circulation and caused it to appear disorganized. It reorganized after it passed the lake and eventually produced the Gillett tornado minutes later.

What We Learned

We found ourselves on the wrong side of the Gillett tornado because I overestimated it's speed. I never thought we would get that close and still not see anything other than rain curtains. The only reason I felt comfortable enough to get that close aside from the desire to understand & learn was because Chris was in the passenger seat. What I learned is that rain-wrapped tornadoes are rain-wrapped, the rain literally obscures everything. There is literally nothing to see or gain from chasing them.

National Weather Service Green Bay Preliminary Tornado Graphic
NWS GREEN BAY RADAR LOOP

-----------OTHER LINKS----------
NWS GREEN BAY WRITE-UP
http://www.weather.gov/grb/6july2015_tornadoes

FULL VIDEO


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