2019-6-20 REPORTS: IA/NE/KS

[JeremyS]

Chased for the first time in 3 weeks on the 20th. Initially, was pretty stoked the night before for a possible great local chase as the CAMs were showing 1-2 big supercells/strong helicity tracks tracking south/southeast across either eastern Nebraska or western Iowa. Woke up in the morning to see a couple of the 12Z CAMs hold onto that idea but the HRRR wasn't too optimistic anymore.
Nonetheless, since it was such a close target I knew I would go out, especially since I hadn't been out in 3 weeks. There were morning storms across northeast Nebraska that were moving slowly east and slowly weakening. However, a cell formed on the southwest side northwest of Norfolk a ways that briefly went severe and even caused a MD to be put out for a possible watch by early afternoon. Unfortunately, that storm weakened as it moved towards Norfolk.
I headed out about 1p. There was still a small almost stationary t-shower just west of Norfolk as I left and headed that general direction. The storm briefly pulsed stronger for a bit on my way there, but once I was within 20 miles or so, it rapidly weakened. Figures, a storm that was there for a couple of hours decides to die once I get close.
Thereafter for the next couple of hours, other small, and short lived cells would pop up and usually within 20 minutes or so fizzle. I slowly made my way up to Wayne and then towards Sioux City, IA. At this point there was one other cell northeast of Sioux City about 20 miles. It was about 5-530 and my plan was actually to start heading home once I made it to S. City and could jump on the interstate south back home. However, once I made it to S. City I thought I would feel pretty stupid if I went home so early and then something still formed or happened in the area so I decided to check out the storm near Hinton, IA.
It too grew stronger and in fact actually had the 1" hail marker pop up on it on GRLevel3(first time all day). I came around to the southwest side of the storm and it too started to weaken and nothing was too visually exciting about it. It was drifting off to the east, but as it was slowly weakening it was producing some non/slowly rotating wall clouds, so I stuck with it for a while.
Finally another cell popped in eastern Nebraska near the river and Onawa, IA. I headed that way and took the Onawa exit west of town about a mile. This storm had a nice base but little else with it at first. Lucky for me though, no longer than probably 10 minutes it suddenly started forming an inflow tail and a wall cloud. There was very slow rotation with it as the storm also slowly drifted off to the southeast. Radar presentation though started looking much better with a bit of a hook on the reflectivity, and a decent couplet on the velocity scans. I ended up dropping south to the next exit down on I-29 at Blencoe, and then took a road back north a bit to watch the storm.
It now had a pretty beefy looking wall cloud but nothing too crazy for rotation. I was able to take pictures and video for about 10 minutes as it slowly approached my location. Just as it was maybe a mile or 2 north of me, it finally started rotating a little harder and looking like more of a "legit" wall cloud. It was about this time I started to get hit with pretty strong RFD winds probably gusting close to 50 mph. I jumped in the car to head east so I could beat it across the road and stay in front of it. However, the storm was also starting to move much more quickly compared to the crawl it was at before. I beat it across the road and went south, stopping after a bit to look back and was disappointed to see everything had fallen apart as the RFD had apparently choked everything off.
At this point, I let the storm head off to the southeast and stuck around in the countryside to take some pictures of the weakening storm and a beautiful sunset with crepuscular rays. I'm glad I had the patience and stayed out long enough to finally see "the storm of the day" in the area.
Storm near Hinton, IA

Storm near Onawa, IA finally starting to wrap up a bit

Looking north from Blencoe, IA

Closest it came to dropping a tornado. Right about this time is when I started to get hit with the RFD

Thought this looked really cool. This was the storm weakening after it came close to producing a tornado. This base was totally rain free for a while, when suddenly this rain shaft punched through the cloud causing a "hole" to appear. Maybe a small wet microburst?

 

[Quincy Vagell]

I remember this day well. I was unusually excited for the prospects in/near Iowa. I was cautiously optimistic until about midday, then I started having legitimate concerns. At 3:30 p.m., I made a rash decision and quickly bailed west from where I was waiting in northeastern Nebraska. I just barely made it to the Nebraska panhandle in time to catch a dying, high-based storm. Thinking the next few days would have a lot of potential in the High Plains, it made sense at the time. The frustrating thing was that I had chased west the day prior and just had a lot of driving back and forth for no good reason.

 

[Brett Roberts]

I had my eye on 6/20 for several days, but was unconvinced it would be worth the multi-day outing (notwithstanding further potential from 6/21-6/23). Only with the 00z CAM suite the night before did I decide to pull the trigger, as strong agreement existed for long-lived NW flow supercells rampaging down the Missouri River Valley from mid-afternoon into the evening. My biggest concern at that point was a rapid transition to HP character. By mid-late morning Thursday, the issue quickly shifted to whether CI was even a given, no thanks to remnant cloud cover from overnight elevated activity.

I arrived in Missouri Valley, IA, by 1:30pm, having prepared for an early show. This was not to be: I crossed back into NE, then meandered the stretch from Blair to Sioux City watching numerous updrafts fight in vain for their lives, including even some that grew to 35k ft. and precipitated. The reality of a complete cap bust became stark by 4pm, when I was forced to cross back to the IA side at Sioux City in lockstep with two turkey tower families. Eventually, the northern of the two sprouted a legitimate updraft with hardened anvil just NNW of town. I watched it for a good hour or so to its SSE. I'm not sure I've ever seen such a visually impressive (relatively speaking) and long-lived storm struggle so mightily against the cap without simply dying in short order. It was very much LP and strongly tilted (perhaps at 45 degrees or greater, from a visual estimate), produced an almost immediate and substantial wall cloud, exhibited periodic RFD cuts and even stubby funnels -- yet only briefly warranted a SVR warning, and never looked like much on radar. I shot a few stills, but haven't bothered to process those.

The southern updraft cluster all but collapsed as this Sioux City LP pulsated and teased chasers, but ultimately came back with a vengeance around 6:30-7pm. We all gradually migrated down toward Onawa as it became clear new growth in that area was the real deal -- or, at least, closer to it than anything else nearby. I was on the late side in making the jump south, but managed to core punch with no more than pennies or so (a situation that appeared to worsen markedly only 10 minutes later, if reflectivity aloft was any guide). Once in the heart of Onawa, the "storm of the day" as it were rapidly organized and birthed a broad but impressive lowering -- similar to the Sioux City LP, but with far beefier updraft structure and a more menacing FFD to go with.

The tornado potential never looked sufficient visually for me to take seriously, so I quickly dove ESE in an effort to hedge toward structure until an alternative was warranted. I was quite surprised how quickly I jumped ahead of virtually everyone on the storm (convergence was not heavy by OK standards, but there must've been at least ~50 chase vehicles around town just prior) -- and I certainly wasn't complaining about it! It was within a 15-minute window here from 7:45-8:00pm, heading E on E54, that I snagged the only photos worth processing. Nestled between the helical updraft and crowds to my W and Loess Hills nightmare terrain just a few football fields to my E, legitimately impressive structure materialized at just the right time for my photography efforts.

The Loess Hills all but forced me to drop S around their periphery, rather than continuing SE to stay in the optimal structure position, which only helps if your effective horizon isn't 50 degrees after accounting for terrestrial obstacles. By the time I emerged into a good valley around Pisgah, you could say the cap was beginning to win.

Again, though, it was fairly striking how long the updraft persisted in a shriveled, LP, and highly sheared state, rather than simply evaporating as one normally sees under the circumstances. The mesoscale environment (presumably sampled reasonably well by the attached 00z OAX sounding) appeared to support a storm evolution and structure throughout the afternoon and evening that was intriguingly unique, if ultimately rather benign.



Begrudgingly assuming a target of DEN was in store the following day, I ditched the LP (still not completely shriveled into oblivion, mind you) just after sunset and made it to York for the night, only for an intense bowing line segment to plow through town around 2am.

 

[cdcollura]

Good day all, Here is my report for storms for June 20, 2019...

MODS: Can you please add KS to this thread title?

Chase Summary: June 20 was an interesting day, with a beautiful supercell storm observed in northeastern Kansas after a long drive on a day that was originally planned to be a travel day anticipating storms over the next few days farther north. There were some areas of potential interest, with a slight risk issued by the SPC from the mid Missouri River valley to the central and northern high plains. A 5% tornado probability was near NE Kansas and SW Iowa as well as near Montana. A 15% wind and hail probability accompanied a large portion of this outlook as of 1630z, with the hail hatched for significant. With slim and conditional chances of seeing storms, I decided to head north to near the Kansas City area, a drive of over 7 hours, but I needed to head north anyway so if no storms developed, no big deal. I headed out of Plano, Texas via Highways 75 and 69 north into eastern Oklahoma, and all the way to I-44 to Joplin, Missouri, and northward via I-49 reaching Kansas City by late afternoon. The atmosphere there and north of there was capped, with no storms expected there. Distant storms developed in Minnesota as well as northeastern Colorado at the edges of the risk area. I headed back west via I-29 / I-635 back to I-70, taking that westward towards Salina, Kansas. A small storm developed to the north and was viewed from initiation late in the afternoon / early evening. I left I-70 via SR 177 to SR 13 out of Manhattan to head north and east to check out the developing storm. This became a beautiful LP storm until late evening along SR 9 near Nemaha County. A special Mesoscale Discussion 1168 was also issued for the area around and near this supercell storm. No watches were valid for the area. The LP storm underwent down-scaling and dissipated after sunset. After chasing, I headed east to Goff, then south on SR 62 and 63 to Highway 24 west to Wamego, then south to I-70 via SR 99. I took I-70 west to Salina, and spent the night there.

Storm Interception Details Are Below

June 20, 7:30 PM - Interception, penetration, and observation of a severe thunderstorm near Marshall and Nemaha Counties in Kansas and along SR 9 from near Vermillion to Corning. The storm was an LP supercell storm. This storm had a striking visual appearance during its maturity, including the "stacked plates" and striations. The core was penetrated during the early stages of the storm, and hail up to 1.5" was observed. The storm also contained light to moderate rain, frequent lightning with some close hits, and winds near 45 MPH mainly in RFD gusts. The storm had a small RFD and rotating all cloud with some small funnels. Conditions causing the storms were surface heating, possible boundary interactions, and a weak surface trough with departing upper trough to the east. Documentation was still photos and HD video. A 2016 Jeep Wrangler was used to chase the storm.

Pictures For June 20, 2019 Are Below



Above: Annotated visible satellite from near 23z on June 20, 2019. The important features of the synoptic environment are denoted, such as boundaries and a solitary LP supercell storm over NE Kansas.



Above: Annotated base reflectivity image of two supercell storms over NE Kansas on June 20 during the early evening. This originally was a single storm that split into two, with the most intense supercell being the southern storm. The velocity image is in the upper-left inset. If you look closely at the "left split" of the storm to the north, it has a slight anticyclonic "curl" in its reflectivity on the western end (clockwise)!



Above: View of intensifying (and beautiful) LP supercell storm over Nemaha County, Kansas. Note the small wall cloud too! The view is to the west.



Above: Low precipitation supercell storm over Nemaha County, Kansas during the early evening of June 20. The distant "left split" can be seen to the far lower right.



Above: Closer view of the left-moving northern split of the LP supercell that is anticyclonic and moving away to the northeast late on June 20. Note the impressive bulk shear and tilting of the updraft.



Above: Who could resist? I just take a humorous selfie of myself as if I am holding up a stack of plates! This was as the LP supercell over Nemaha County, Kansas started weakening / down-scaling during the evening of June 20.

Note: For DETAILS on this storm / setup as well as others in June 2019 … Please visit the link BELOW for more information!

Sky-Chaser Web Site (Chris Collura - KG4PJN)