Tuesday, July 28, 2015

07/13/15 Kewanee, IL Supercell

A supercell nearly produces a brief tornado on this evening northwest of Kewanee, IL

On July 13th, I once again decided to storm chase in west-central Illinois as a substantial risk of severe weather was in the forecast for much of Illinois. I started the day at my apartment watching a decaying Mesoscale Convective System (MCS) on radar move across northern Illinois and push an outflow boundary southwest toward Peoria, IL. Knowing this outflow boundary would be influential to afternoon vigorous convective development I targeted this boundary across central Illinois most of the afternoon. By mid-afternoon, I began to head north  on IL Rt. 40 from Peoria, IL toward the I-80 corridor as strong surface heating began to push this boundary farther north. Most of the day a strong cap was in place which was not predicted by the weather models. This was caused by surface winds veering from the southeast to the southwest throughout the day allowing an Elevated Mixed Layer (EML) to advect over much of west-central Illinois. This would allow extreme instability to build throughout the day and keep a "lid" on convection until 4:00pm when convection initiated along the outflow boundary. I found myself by 4:00pm along I-80 near Sheffield, IL as agitated cumulus began to slowly break the strong capping inversion present. This area along the I-80 corridor featured extreme instability with 6,000J/kg of CAPE, 0-6km shear at 50kts, a supercell composite of 16, and a moist boundary-layer with dew points darn right oppressive near 80ยบF. This was quite a volatile environment in place for severe storms and supercells in this area which definitely raised concern for some rather wicked storms during the evening. I sat along the interstate for a little bit waiting to see where convective initiation would begin and which storm I wanted to latch onto. I had a choice go east on I-80 and target a developing supercell or go west and target a supercell that had developed near Davenport, IA and chase this storm as it crossed the Mississippi River. I chose to head west on IL Rt. 92 as this supercell was more organized at this point. Shortly after 5:00pm, I headed south on IL Rt. 13 and then east on U.S. 6 setting up just south of I-80 southwest of Geneseo, IL. This is where I got my first view of a massive rotating updraft from this supercell which was spectacular to see especially in Illinois. This supercell had some rather nice mid-level striations which I photographed while hearing a constant rumble of thunder and seeing some close cloud-to-ground strikes being thrown out of the anvil as well. Those are the lightning strikes that really freak me out! This supercell continued to track southeast through Henry County, IL and was at its strongest northwest of Kewanee, IL. I got some great shots along IL Rt. 81 as this supercell tried several times to wrap up and put down a brief tornado with multiple funnels which I photographed. Despite the favorable environment this supercell struggled to contain its outflow rather quickly and this was easily observed. You could also observe the fact that this storm did not have enough inflow for tornadogenesis which prevented the rotation from tightening to allow vertical stretching to occur. With that being said, she sure did try to put down a brief tornado a couple times. I tracked this supercell for a hour or two ending up just south of Bradford, IL where it dissipated. I then stopped at a local wind farm south of Bradford, IL to shoot some shots of an amazing sunset as well as some stout convection to my north and east. I arrived back home in Peoria, IL shortly after sunset after a rather fun local storm chase. A detailed analysis that discussed why a more widespread severe weather outbreak did not occur from the National Weather Service (NWS ILX) can be found here. I've added photos from this chase day below:

First view of the beastly rotating updraft of this supercell!
 Along IL Rt. 16 southwest of Geneseo, IL
Quite a wicked structure on this supercell!
Mid-level striations clearly showing the strongly sheared environment for July-standards!
New updraft begins to be seeded to the southwest flank...
Back-lit convection!
A wide-angle shot!
Supercell beginning to cycle with this new convective updraft forming!
A pretty cool close-up shot of this supercell's updraft!
Crepuscular rays as more convection forms to my west...
I head northeast to get up-close to the RFD of this supercell...
 "Rotating mass"
It funneled a few times at this point back in there!
Farther east...I capture some structure shots!
A wide-angle shot of this supercell!
"Rotating skies"
Hmm...funnel halfway down...
"Spinning away"
Cycling once again as it's struggling to keep its outflow contained with a lack of inflow...
Still spinning here, but becoming more and more outflow dominate!
Outflow dominate supercell!
Some really cool clouds overhead just south of the pouring rain...
Some photo-ops at a local wind farm south of Bradford, IL
I goofed around a bit here...
A powerful back-sheared updraft forms back to my north along the dissipated supercell's outflow boundary...
I had to be patient to get this shot as I had to wait for some mid-level clouds to move to my east!
Near sunset I shot this amazing shot!
Convection about 30 miles to my northeast!
Sunset is getting closer...
"The setting sun breaks through the clouds"
Another photo-op at the wind farm!
Mammatus clouds near sunset!
Golden-hour begins as the setting sun creates some dramatic colors to my northeast!
"Golden-hour convection"

After a rather quiet spring in central Illinois in terms of severe weather the last two months have been very active in this area. Even though this day did not live up to the hype that was being predicted the potential was sure there and very real. Cities, towns and communities in Illinois were rather lucky that there were not any significant tornadoes and/or a widespread damaging wind event on this day. Anyhow, I took a week long vacation to the Northern Great Plains this past week photographing many parks/national monuments in the area and I also chased some storms as well. I'll update once again with several more posts in the coming weeks.