July 13th, 2015 Ottawa, IL Supercell
Tornadoes: 0
Largest hail: N/A
Highest Wind Gust: N/A
July 13th is a significant day in weather history for Central Illinois, when on July 13th, 2004, an F4 tornado completely obliterated the Parsons Manufacturing Plant outside of Roanoke. On this day, 11 years later, it appeared that a significant severe weather and tornado threat could materialize right over the same area, under a relatively similar setup.
A northwest flow pattern was set up across the corn belt, with extreme CAPE values of 5000-8000, along with oppressive (and disgusting) dewpoints in the lower 80s. Shear above the low levels was strong, but within the low levels was questionable. An MCS came through early in the day, laying out an outflow boundary that began to retreat north towards the I-80 and I-39 corridors. This boundary was the main hope for the low level shear and helicity that could ultimately produce a potentially intense tornado. In addition, supercells early on were forecast to evolve into a raging squall line and/or derecho, prompting a large Moderate Risk from SPC. They also outlined an area of 10% hatched tornado probablities across northern and central Illinois.
Below is an animation of the 925/850/700/500/300mb winds at 00z on July 13th. Southwest surface winds could potentially get the job done with the NW flow at 500mb and above.
The 18z DVN sounding showing an eroding cap with mounting instability. Surface winds were weak, but the extreme instability could be able to compensate for it.
An MD came out for a 95% chance of a watch:
And indeed, one was later issued:
My main objective for the day was to keep track of the boundary. Mesoscale interactions are a huge deal around here for tornadoes. A storm eventually started going up right on or just west of the boundary over Bureau County, only about 10 miles north of my house.
We headed out the door at this point and found a position about 3 miles west where we could watch it mature. A few different updrafts developed and fizzled out, and finally one took hold and developed into a more mature storm.
We took off and headed up I-39, trying to get a view of the base. We got a visual of it south of Ogelsby, and the beginning of the first cycle of the supercell was evident as a wall cloud was developing underneath the updraft.
Once we got to the intersection of Route 6 and I-39 near LaSalle, there was an instant chaser convergence. Live Storms Media streamers were pulled over on the shoulder with about a dozen other chase vehicles. This wouldn't be a big deal out in the Plains, but it was pretty neat seeing all these chasers 15 miles from my house. There were even a few PECAN mobile mesonet vehicles chasing, leaving their normal domain of the Plains, desperate for something usable to their research.
We worked our way west towards the direction of Ottawa, trying to find an area without trees. We finally did, and watched some very decent rotation with the wall cloud along with other supercell features. The rotation was even rapid for a brief time.
Here you can see the inflow band and the wall cloud, along with what may be the developing shelf cloud of the first wave of RFD.
Cell phone video shot from the same spot:
The storm started to get ahead of us, meaning we had to reposition ourselves. We almost got to Ottawa before we saw the structure of the supercell in all its beauty: a massive mesocyclone with a huge RFD cut wrapping around, and an incredibly photogenic wall cloud.
We sat in this spot (stupidly) for several minutes, watching the meso churn away to our southeast, moving away from us. Once I finally came to my senses, we started off in the direction of it eventually having to manuever through what is the red light hell of Ottawa, IL. Every light in that town is red every single time we go through. It never fails. Ever. Chasers beware the next time you encounter a storm in this area. We were now way behind the storm, but could still see the RFD clear slot, and would still be able to see any tornado. It was still incredibly photogenic, although I only got cell phone snapshots and not DSLR ones.
The roads in this area were actually incredibly good, with a general 1x1 mile paved grid. But with the storm generally beginning to wane as we approached Dwight, us getting further and further from home, and more storms further west, we decided to abandon the storm with this last look at it:
We began heading west with hopes of catching the supercell that had encountered a similar fate as the previous one: good structure and organization, but no tornado. That supercell was backlit nicely by the lowering sun, allowing a good view of the general health and structure of the storm from 50 miles away.
At the point this picture was taken, it looked like it had a shot to maintain or intensify its strength. However, it appeared fuzzier with time as we kept heading west, and radar confirmed that it was indeed weakening. After seeing that it was no longer worth watching the western storm, we stopped at a Burger King near Wenona for a quick bite to eat. It was during this stop that I saw the flooding of social media with pictures of an incredible tornado in a Marginal Risk in Kansas. I wasn't really upset by it because it was so far away, but it was just a little reminder that nature doesn't give a crap and will do what it wants. After we got our food, we started heading north up I-39 towards home. Another storm was forming right over the highway 75 miles to the north, near Rochelle. White hail shafts were even visible from that distance:
We got towards home as more storms were developing just to our north and west. Several chasers, desperate for something else to chase, were flying through an intersection I drive through nearly every day, near Granville. We pulled over, waiting for something to really establish itself. This view is of convection to our north and east:
We eventually decided that nothing was worth pursuing further, and went home. Here, one of the storms actually went severe, and I was out at the end of my driveway watching it approach. It was nothing incredible, but it was still really amusing to see a couple vehicles of what I suspect were chasers going right by my house. The storm went over with just rain, but I did hear a few pinging hailstones once in a while. This storm passed by, and another storm with some elevated supercell structure was coming right at me. I set up the DSLR and started time lapsing. The sunset lit the storm up pink as the occasional lightning bolt was spit from the anvil.
The full time lapse:
The solid-looking gust front passed through with some more lightning.
Compared to the forecast, the day was certainly a disappointment. The outflow boundary, which was set up right where the Ottawa supercell was tracking, had washed out shortly before the storm developed. The lack of low level shear likely prevented it from producing a tornado, despite the extreme CAPE, moisture, and high shear values above the low levels. Still, it was a nice supercell to chase and it was extremely local.
GPS History:
SPC reports and verification:
The funniest part about that map is that the Moderate Risk area was basically barren, while nearby areas were full of reports. I don't blame SPC one bit though since this was a huge troll event.
