Statistics:
| Initial Target: | Missouri/Iowa border on I-35 |
| Departure: | Bolingbrook, IL 10:30 am CDT |
| Arrival: | Bolingbrook, IL 1:00 am CDT |
| Intercepts: | Madison County, IA 6:00 pm CDT |
| Tornadoes: | 0 |
| Hail: | Severe Dime to Nickel (0.75 - 0.88 inch) |
| Wind: | Non-Severe (not measured) |
| Features: | Wall Clouds, RFD Clear Slot |
| Miles: | 730 |
Summary:
| Exhausted from previous day, would only chase if significant tornado threat forecasted. SPC forecasts 25% with cross-hatching, so targeted western Missouri/Iowa border. Coming into Des Moines spotted thunderstorm with severe warning. Dropped southwest into Madison county and intercepted two wall clouds with possible rotation, RFD clear slot, but no tornadoes. Met pair of chasers and formed a caravan until severe squall split the party up. Caught first severe hail on I-35 trying to go south to new warnings. Couldn't break out of squall, called it a chase at 8 pm, heading home. |
Crew and Equipment:
| Solo Chase. Equipment consisted of a NOAA weather radio, cell phone, and TH-F6A Tribander. Photography by Skip Talbot |
Details:
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When you drive over 700 miles the previous day, and get 6 hours of sleep, you don't feel much like gallivanting around the countryside some more. I came home close to 2 am and was greeted by this Day 1 Tornado forecast from SPC. I can't pass up a 25%... I was going again. A 45% for severe wind was forecasted in southern Iowa as well, bringing the risk level up to HIGH.
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| After helping Dad with his PowerPoint presentation, I got on the road a little after 10:30. I took 80 west toward Des Moines. Tornado watches went up along the way. The area I was after got a PDS Red Box (enhanced tornado watch) or "The Kiss of Death" for its ability to make chasers bust |
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Is this supposed to be a lake? Half of central Iowa was under water with flooding from previous thunderstorms. Today wasn't going to make the situation any better. |
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| Approaching Des Moines I came upon the darkening horizon of a looming storm. Looking west. Storm is moving east at 30 mph. |
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| Contrast enhanced mammatus. Much more ominous then the ones I saw the other day. The storm had a severe thunderstorm warning on it. I was thankful it wasn't tornado warned, I probably hadn't missed the show. |
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| I got onto I-35, still on route to my original target area, but I knew I had my storm. I wasn't about to ditch this cell for ones that may or may not exist further south. An interesting feature here. It looks like a long inflow feature, beaver tail probably. Knowing only mediocre storms in hazy IL, features like this or quite new to me. |
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I exited 35 and snaked my way along some county highway I don't remember the name of. You can see it in the Mapquest capture below. Through the hills and trees I could make out some sort of lowering. I came into a nice flat clearing that lead towards it. Is that a.... Yes! Its a wall cloud! I pulled off, snapping a few pictures hoping to get lucky. Don't worry, the rest of the shots are tripoded. |
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| Here's the road network I had to deal with. I was looking at the forecast for today and Missouri held promise, but storm chasers call it Misery for a reason. Awful twisting roads with hills and trees. I hoped that by staying in Iowa I wouldn't have to deal with that. That wasn't the case here in Madison County. This map would have been handy at the time, my road atlas only showed major highways. |
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| Radar at about this time (5 pm), which also would have been nice to have. The sups that produced tornadoes in northern Missouri had the more impressive echoes. Note the squall coming in fast behind by the cell I was on (near Des Moines). I would have never caught the Missouri storms (or the Kansas/Nebraska ones that produced as well). |
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| Nice crisp shot of the approaching wall cloud. Storm moving east northeast and I'm looking west southwest, which made me realize it was going to pass pretty close and I might have to move if things got hairy. Storm still had only a severe warning. |
(click to enlarge)
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| I setup the tripod outside the car. I was starting to discern some movement. Scud was feeding into it dramatically, but it appeared the wall cloud was also moving right to left. |
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| This shot shows the color a little better. You could see the green
core behind the wall cloud highlighting its top like a neon light.
Note a second wall cloud forming in the distant background. It was
ragged and unorganized at this point so I wasn't giving it much attention.
Looking west. Cars whizzed by me headed right for it, most likely not realizing the threat. If a tornado dropped, they'd be in grave danger.
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(click to enlarge) |
| Here's a two frame, contrast enhanced, animation showing the movement in the wall cloud. At the time I thought it was rotating, quite slowly, but rotating. After really pouring over these frames it appears the center rear of the wall cloud is pushing forward and the edges are being pushed around the edge toward the back. From the side it would look like a rotating movement, but I don't think this counts. It's more of a bowing action. See the wall cloud video at the bottom for a time lapse analysis. Des Moines issued a Doppler indicated tornado warning on this cell a little later so I'm sure something in there was spinning. |
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| If this wall cloud, which did have much motion to it, wasn't rotating or at least very strongly, it would shed some light as to why it didn't produce. The RFD (rear flanking downdraft) is starting to punch through. I was conserving memory, expecting imminent tornado formation. This is my first up close and personal experience with a wall cloud, however. Everything I knew about them up to this point was from online reading material and spotter videos. |
(click to enlarge)
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| Clear slot forms as the RFD punches through. This feature usually
precedes tornado formation by only a minute or so.
One of the most awe inspiring aspects of this chase was being able to feel the winds. As the wall cloud approached, strong inflow picked up heading straight into the lowering. Even more impressive was, as the wall cloud passed by to the north, the wind changed direction to follow it. Very cool. However, the best part, which also made me a little uneasy, was when the wall cloud was at its closest: The wind was no longer horizontal to the ground, but had quite a noticeable upward vector. Dirt and other small crap was flying up off the ground and getting in my eyes, hard to shoot video with that going on. The RFD hit me and with the snap of a finger, the wind changed direction from North to South. The blast wasn't cold like most downdrafts, a good sign in tornado formation. |
(click to enlarge) "It's the suck zone." - Dusty (As a post-Twister chaser, I can't help quoting the movie.) |
| Here's a two minute video of the wall cloud, much of it sped up four
times so you can better see the motion. The gaps between the clips are
when I was shooting stills or conserving the memory in case it dropped a
tube. I apologize for the oscillating focus. I'll turn my auto focus off next time and leave it set to infinity. |
Movie, click to play (5.5 MB 320x240 WMV)
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| Rain is starting to fall through the wall cloud and clear slot. Either the updraft was weakening (more likely) or the rain was wrapping around the updraft (less likely due to lack of tube formation). Looking north. |
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| Here's a close up of the clear slot. The RFD and clear slot is a concept I was introduced to this year. I'm glad I was armed with that knowledge going into this chase. |
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| The second wall cloud forming to my west northwest. It was filling in rapidly, and knowing the movement of the last wall cloud, this one was going to push off even further to the north. I was going to have to give up my spot and move if I wanted to continue observing it. |
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| One last shot at the first wall cloud as it becomes outflow dominant and fans out into oblivion. |
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| Low level scud with rapid motion between the two wall clouds.
Looking northwest.
This is about where I said to goodbye to my spot and found a gravel road snaking its way through hills and trees, but it lead closer to the storm. This road was "Bob's road" straight out of Twister. There were construction cones periodically placed in the center (not a good sign), and that's about when I came to a rickety wooden bridge. It had a sign next to it specifying a weight limit with a picture of a truck. Shibster is no truck so I attempted it and made it across.
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| Just past the bridge I came upon a car nestled in a valley,
the driver intently watching and filming the second wall cloud. Ah ha!
Someone who probably realizes what's happening here. I pulled in
behind and we both got out to talk. Turns out he was a meteorology
student at Iowa State out chasing. I finally met another chaser on the
road. We talked for a bit until I suggested moving up to the top of
the hill so we could see the base of the wall cloud. There was a short
gap there when we didn't have a visual on the second wall cloud, but I doubt
anything dropped. A few locals also pulled up to figure out what was going on. One asked a question that I'm sure tops the chaser FAQ, "Is there going to be a tornado?" Jeremy, the met student, replied, "I sure hope so!"
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| Suddenly and without warning (dramatic phrase) a cone formed between the
wall clouds. It had crisp edges and came to a sharp point.
Jeremy shouted, "There it goes!" I scrambled for my camera. By
the time I fired off a picture the object had fanned out into this shape.
It then became clear we had just another inflow band. This one really
got us good though. The storm was going HP quickly, which was going to lead to a messy chase with limited visibility or a dangerous rain wrapped tornado. |
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| Escaping south about a mile or two to get ahead of the storm and into a better viewing location we came upon a chase crowd of about 6 cars clustered along the entrance to a gravel road. They appeared to be local yokels "ooohing" and "aaahing" at the scud and exclaiming that a tornado was going to drop, even though I knew these storms were crapping out on us. We moved on past them and stopped to analyze our position and the storm. A car pulled in behind us. By some fluke coincidence it was one of Jeremy's friends, James, another met student at Iowa State. He bagged his first tornado on the 22nd, a day that I reget not having chased. The three of us caravanned for awhile until it became obvious we were chasing junk. James had seen the radar before he left Des Moines and informed us a squall line was moving in from behind these cells. Sure enough we could see the shelf coming in out of the northwest. James and Jeremy called it a chase and we parted before the shelf hit, and boy did it hit hard, with strong winds and torrential winds. |
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| I went south on I-35 hoping that the southern flank of the line was workable. I started getting some hail and pulled over to get video. Cars were clogging the overpasses trying to avoid it. Most of the stuff was pea to half inch but a few dimes and nickels bonged the shibster. My first severe hail! Here's a short video. |
Movie, click to play (560 KB 320x240 WMV) |
| It became clear that this line was impenetrable. I encountered flooding on some of the roads marking that it was time to call it a chase. I took 92 east to 65 north, I-235 to 80 home. I also somehow managed to keep up with the line the entire way home. Breaking out of the rain just as I got home five hours later. Shibster also picked up a nail in his tired just before I got in, springing a slow leak. The tire was flat by morning, but I took him and they should be able to patch it up. Somewhere on 80 I stopped at a KFC. When the employee serving me learned that I was up chasing he told a vivid story of how he saw a tornado many years ago, describing and acting it out as "a giant walking through the forest plucking trees and tossing like they were nothing."
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| Conclusion: Not a bad chase at all. No tornadoes despite the high risk, but the wall clouds, clear slot, and my first severe hail definitely made it worth the trip. It was also nice to meet a few other chasers. I like the company of having friends along for the chase, but it was nice being able to talk about inflow and downdrafts with somebody for a change. The day was a big one for the veterans and Plains chasers. Picturesque tornadoes in Kansas, Nebraska, and Missouri with some chasers catching several in one day. Some day I aspire to be that good.
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Lessons learned:
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