- Andrew Pritchard
July 13 2015 | Ottawa Illinois Supercell
This one was a head scratcher. It's not just that again, my tornado drought continues - but this one ended up nothing like I expected it to. And that's not even necessarily a negative thing. Yesterday should have been extremely frustrating and hard to chase, but it wasn't at all. Instead of high precipitation storms that quickly merged into a line/bow and quickly raced away from us, we had highly visible slow moving supercells that never merged or congealed. But... BUT... traditional logic would have said hey, individual isolated supercells that lasted for hours, must have been a real tornado-fest, right? But no, nothing.
The 11:30 AM Day 1 Tornado Probabilities highlighted a 10% hatched area for significant tornadoes over central and northern Illinois.
11:30 AM Storm Prediction Center Day 1 Severe Weather Outlook showing a 'Moderate Risk' over much of Illinois, largely for a damaging wind threat.
Extreme instability was in place for late morning on. A bow echo traveled south out of Wisconsin but quickly died as it entered central Illinois during the late morning. That left the entire target area under sunny skies, with an outflow boundary simmering under the July sun. Temperatures soared into the 90s with dew points around 80 degrees, leading to surface based cape values around 7500 j/kg per mesoanalysis during the mid-afternoon. The negatives, unbeknownst to us at the time seemed to be weak surface winds, and perhaps some dry air working in in the lowest 100-200 mb that lead to very low instability in the lowest portions of the atmosphere that are so crucial to tornado development.
Tornado drought year 3: Dream team re-assemble:
Colin and I finally chased this one together, with my brother Wil riding along. Wil and I left Urbana around 11 AM meeting Colin in Bloomington shortly after 12, riding up Interstate 39 to the La Salle area which had been my target for some time. We spent a couple of hours baking under a sky that just screamed tornado day. Patches of blue sky between low level moisture signaling cumulus clouds racing to the north.
Around 3 PM the first towers began to test the cap, and after struggling for an hour or so to break through, we had storm initiation. We briefly gave chase on a storm near the Dwight area, but once a second area began erupting back toward La Salle in what was my preferred area, we flipped around to intercept. Stopping briefly near Streator to let the storm organize, it became apparent that this was our play.
Radar at 3 PM shows the first returns on radar to our north:
After nearly 2 hours of slow organization, we finally have a legitimate storm to persue:
We zig-zagged northward with the storm base finally coming into view near Ottawa. Immediately it appeared that we'd be in for a tornado show in mere moments. We set up along the shoulder of a gravel road with a soy bean field that gave us a great view of the thunderstorm updraft. A rear flank downdraft punched in, curling around a wall cloud that seemed to be scraping the tree tops. The three of us were certain we were minutes away from watching a potentially significant tornado right in front of us. A local deputy pulled up and told us he'd just dodged some large hail to our west and had retreated back to our location, and began snapping some photos of his own on his cell phone. The storm chaser - police relationship has been strained in locations in recent years, but this interaction was beyond pleasant. After chatting about the storm for several minutes and seeing that we apparently had some time before a tornado touched down, we thanked him for his service and were on our way.
Incredible rear-flank downdraft (the clear area breaking through the storm) with a large wall cloud nearly scraping the tree-tops. Surely we are moments away from a tornado!:
Colin and a local deputy discuss the sky:
Another view of the entire supercell as it attempts to produce a tornado south of Ottawa:
I've had a long-standing love for wheat fields. One of my favorite meditative spots near home is a wheat field on a glacial moraine overlooking the farm fields of southern Champaign County. The contrast that these amber waving fields of grain provide up against nearly any sky is unbeatable in my books. As we crested a hill south of Ottawa, what I thought was minutes from watching a tornado snake down from the sky and spotted a golden wheat field in front of us I could hardly contain myself.
What would have been a dream-shot for me, the supercell comes oh-so-close to wrapping up and producing a tornado over a golden wheat field:
Colin quickly stopped the car, I cursed my tripod as I struggled to attach the camera, and began filming in anticipation. But again, the sky spun and spun, and then sure enough, things slowed down and lost their organization.
This is where the details will stop. We followed the storm for another hour, southeast toward the town of Odell, along Interstate 55. The supercell had allowed its gust front to surge ahead, which had cut off surface inflow and any hope of producing a tornado before the sun set behind the western horizon. We entertained the idea of intercepting a second storm northwest of Bloomington, IL - but upon plotting a course and gaining visual of this storm, it evaporated into thin air leaving a pink sunset for us to enjoy over some gyros/italian beef/hamburgers in Bloomington.
There are several sufficient answers to today, some of which I listed above. It's just so odd how it was so completely against what I expected - and not even in an entirely bad way. I feared going into the day that we'd have high precipitation, low visibility storms that would quickly merge into a messy cluster and race away from us. Instead, we had storms that remained isolated for their entire lifetime with high visibility. But considering that - isolated storms in this environment at a quick glance would have favored a potential outbreak of tornadoes. Instead, we had several hours of isolated, photogenic storms, that never produced a single tornado. Amazing news for the residents, and though my 3 year tornado drought continues, still good news for my camera.
Video and time lapse from the chase: