Saturday, July 01, 2017

Summary of the day: June 29, 2017

Thursday was supposed to be the day.

We outlined 4 areas, all with pluses and minuses.  The #1 target was northeastern Nebraska. #2 was southeast CO. #3 was northeast KS. #4 (not chaseable) was around Buffalo, NY.

We got going north to our initial target of Norfolk, as the surface low was very close to there. We had a quick lunch there and came out to see big towers going up to our northeast, right on the warm front emanating eastward from the low.

We followed it along and it grew rather quickly as we approached it. Once its tops reached about 50,000 feet it got severe warned. It even had a TBSS on it.

The storm quickly split and started rotating. As we approached it, we got up on a hill and saw a couple of attempts but it couldn't focus its rotation.  We got back on the highway and the storm continued to strengthen, as did its RFD. We had to stop a couple of times a) to watch and b) to avoid the rotation on the storm.

Navigation became an issue, though, as the storm was heading straight for Sioux City. The problem with that is the Missouri River, which has one crossing right there and another about 30 miles to its south. We decided to tuck in closely behind the storm, cross the river and then get ahead of it once again. We passed through some heavy rain and some hail along the way--through Sioux City there were some hailstones that might have been quarter-sized, maybe a touch larger.

As we once again got in view of the storm, it showed us some decent structure but then another storm started to go up to its south. Destructive interference was occurring so (after a flat tire scare) we dropped south to see if the south one could organize.  And it did.

The roads, hills and trees made it difficult to get more than a glimpse of the storm, but we could see (both visually and on RADAR) that this storm was quickly organizing.  We finally found a good option south of the storm where we could see it, and a glorious scary supercell was right in front of us.  It had a fairly round bowl mesocyclone, and a good inflow tail was hugging the ground.  It made a few attempts to produce a tornado in the green hue, but (again) couldn't quite focus the rotation.

After that, the storm lined out and then another south one tried.  That farther south one didn't do as well and linear forcing was becoming more prominent, so we called the chase for the day and for the trip.

We had dinner at Texas Roadhouse in Sioux City and stayed there for the night.

Summary of the day: June 28, 2017

Wednesday was a day with 2 potential locations to chase and another that we knew would light up but wasn't reachable.  The two locations were eastern Colorado and southeast Nebraska. Eastern Colorado was a lesser play because the moisture had been flushed, so we opted for the southeast Nebraska play.

We were expecting primarily outflow-dominant supercells because the models had been consistent in veering the winds ahead of the slowly-advancing cold front. But a detail in my H5 analysis gave me hope: there was a subtle thermal ridge/trough couplet over Nebraska that the model hadn't picked up on. So if it would time favourably, perhaps pressures would fall and winds back at the surface, giving us a better tornado chance.

After lunch in York we came outside to see significant towers bubbling up to our east. Visible satellite imagery also showed an area of significant agitation in the cumulus field over the area, so we hurried in that direction. Once we got east of Lincoln, towers were really starting to show great vertical development, and one looked like it had breached the cap near Nebraska City.  Soon it became a full-blown storm crossing the Missouri River.

After navigating up the bluffs and through Waubonsie State Park, we came to an opening where we could see that the storm was really ramping up its rotation. We stopped to have a look and, around 3:43 PM, we caught the first tornado of the U of M 2017 storm chase trip!

The storm somewhat disappeared into the terrain so we continued east. The mesocyclone decided to produce a very pretty vortex on its edge. We stopped for more pictures and the storm produced a second tornado for us.

After this, the storm got rather messy with new storms going up and interacting with the existing ones, so we looked to our south.  At that point we saw a new updraft rocketing up, with amazing motion on a wall cloud. We were in a weird place relative to the storm, one I don't usually place myself in, northwest of the circulation. No precipitation was on our tail, so we had time. The storm really ramped up its low-level rotation and it had the chance to produce a tornado a couple of times, but it never quite focused the rotation enough. After finding a 2 inch hailstone in the grass, we opted to keep following along with the storm until it got messy because of more interactions.

At this point, there was just a big mess of storms interacting with one another, so we opted to drive back to the hotel.  We started out north and saw on the RADAR that we would be going through a nasty hail core, so we doubled back south to get around the complex.  Also, RADAR showed that somewhere upwards of 8 inches of rain had fallen there too.

We got south and west, and another storm decided to get strong in front of us--bonus supercell!  It showed us a nice wall cloud and a possible tornado, but its main characteristic was that it was throwing out tremendous lightning bolts all over the place, and we got some really good pictures.

We got in late to our hotel in Lincoln, so dinner was a quick grab-and-go along I-29.

Summary of the day: June 27, 2017

Tuesday was an interesting day with a lot of potential, although some weaknesses in the upper flow were evident.  We targeted the NE/CO/KS border.

Morning moisture was pretty good, with lower 60s (F) aiming for the area. Storms were suppressed for a while so we were able to get lunch in Sterling, where it was really hot (38 C) and the Verizon people were unable to help us with our jetpacks.

Cumuli started bubbling up in southeastern Wyoming, and eventually some storms morphed out of that.  We drove northeast into the Nebraska panhandle, watching as the storms became a sort of north-to-south broken line.  A lead cell went to our north and we jumped ahead of the line to be in place if that storm took over, but stayed far enough south so that if tail-end Charlie took over, we could target it, too.

The lead storm didn't change much, so we drifted back south to see what the one on the south end of the line would do.  It was a nice shelf with some curvy rain curtains coming out of it, but further storm organization looked unlikely.  So we moved east and then north, passing by an air force RADAR on the way to our hotel. The band of storms approached us as we were just south of the hotel, it got severe, producing wind gusts in excess of 100 mph to our north. It hit us at our gas stop with some pretty strong winds, although I don't think they were severe at that location.

We got pizza in the lobby and had a good evening by the fire.