The Setup
This looked like a chance for strong tornadoes in Nebraska. CAPE was up to 4,000 J/kg, a warm front was lifting northward through the state, and low-level and deep layer shear were sufficient for supercells and tornadoes.
The Chase
We had gotten the chase van stuck in the mud the evening before. My first task of the day was to get it towed out and back to our hotel in Lincoln to pick up the guests again. I took an Uber back out to where I had gotten stuck, and by the time the towing company met me there, I had decided to try driving out myself. I managed to slowly get the vehicle unstuck from the side of the road.
After I picked up the guests, we went to Walmart and ate lunch at a Mexican restaurant in Lincoln. From there, we drove west to Seward, spent about 15 minutes at a city park while I analyzed data, then continued westward and then northward. I aimed the van toward St. Paul until we could see the storm base on the southwestern horizon. We stopped once to watch the storm as it became tornado-warned. I believe I saw a funnel from this distance. Indeed, a tornado was reported near Cairo, so I believe we saw an initial, small tornado.
We were getting some forward flank rainfall, so I decided to go a little west and take a paved road south until we cleared the precipitation.
The Tornado
The tornado started from a rotating portion of the front of the mesocyclone. The look was not of a wall cloud and updraft base with a rear flank downdraft cutting into it. From my perspecive, the forward part of the mesocyclone folded around and wrapped around from the south to north. As this happened, a narrow, white funnel formed at the center of the wrapping tornado vortex. This white funnel was low contrast and difficult to see at first, but it picked up dirt and debris and turned black, increasing the contrast. It became quite large and black from our relatively distant perspective, about five miles to the east of the tornado.
Wrap-up
After the frustration of getting stuck in the mud the night before, it was fun to see a tornado and have a leisurely end of chase by around 7:00 PM. I somewhat lucked out on the intercept as no rain obscured the tornado during its early lifecycle from our direction. We saw it wrap completely in rain and missed the rope-out. Maybe we would have seen it had we looked back, but we were focused on staying ahead of the expanding, wet RFD.