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April9


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April 9th, 2011 - Mapleton, IA Cyclic Supercell

That's right, a chase account with both the words "Iowa" and "Tornadoes" in the title. Not just a cap bust lol. What a chase day (or night, really) this turned out to be. Had some pretty substantial parameters in place (especially given how relatively early it still was in the season) over extreme northeastern NE and northwestern IA.

We first drove to North Bend, NE in hopes that things would fire off to the west. We sat just north of there in hopes that these towers would take off. They eventually would, but before they did, something started showing pretty decent tops on radar farther to the north. We left these behind and blasted towards West Point, NE.


Here we are under the base of our storm just west of Onawa, IA. The lighting made things really tough to shoot (really bright diffuse sun under the base leading to over-exposure), but that wasn't my only problem. Several days prior to this chase, I had just gotten my wide angle back from some factory repairs. It's internal lens firmware was out of date, so it didn't want to play nice with my camera. Got it back for the chase, which was a massive relief, but I didn't think to check if its focus was calibrated correctly. As you might guess, it wasn't. I put it in manual focus and trusted that the focusing scale on the lens was correct, failing to check my shots for sharpness. When shooting storms, you're usually pretty safe putting the focus at infinity and ticking it back just a touch. That's what I did. Unfortunately for me, infinity focus, according to my newly-mis-calibrated scale, was about 4 feet in front of my face. So while I thought I was getting sharp images, I was actually taking blurry shots with a terrible vignette. The center of the frame was relatively close to being in focus (I said relatively) while the corners were horribly soft. Didn't help that I shot wide open around f/3.5 almost the entire chase either. Oh well, live and learn. The lens (Tamron 10-24mm) has since been sent back to the factory for repairs. It came back slightly sharper, but its distance scale is still mis-calibrated. So to avoid making this same mistake in the future, I put a dot of white paint on the scale where infinity actually is.

</lensrant>



Another shot further down the highway, still just west of Onawa. That's Cody, Josh, Craig, and another chaser on the right. They were riding together behind Chris and I, who's on the left. Wish I would have appreciated the storm's structure more at the time. It had a golden elevated base, a nice little vault region to the right, and some beefy convective inflow bands above.



Here's a shot mainly for the structure enthusiasts out there. As we waited for a train to pass through Onawa (longest train of my life lol) I took a shot up through the sun roof looking back at the insane RFD cut. You can really see the storm cranking now. We were worried that it was going to try and produce before we had the chance to get out of town. Luckily it waited for us.



East of Onawa now, and this thing starts doing all kinds of crazy things. It started producing some very dusty circulations. This was definitely the most impressive one. While it didn't have a condensation funnel close to the ground (think there was one, just below the base) it was still kicking up a ton of dust. This thing was pretty consistent and stayed on the ground for at least several minutes before passing the highway. You can also see it pulling in smoke from what was supposedly a fire caused by a lightning strike. Pretty sweet!



Took a two-image pano of everybody stopped in front of the storm. Craig's taking a shot looking back at me lol. Above their van you can see how rounded the base was becoming as it pulled in more inflow bands.



Got a bit out of position and behind the storm now as we tried to keep up with it on winding Iowa highways. This is just before the storm planted an EF-3 tornado, devastating the town of Mapleton, IA. Our lighting was bad, as it was starting to get dark (thanks to another storm that popped up to the WSW, blocking out the sun). You could still tell the storm was strengthening and organizing based on its inflow though. Note the dark lowing just behind the hill.



Here's a terribly contrast-enhanced shot of the broad funnel/circulation as it began to drop on Mapleton. A bad photo, but a tornado is a tornado. Probably not even a shot worth posting, but thought I ought to anyway since this was the main tornado of the daytime event.



The inflow into this storm was insane. The ground was also pretty dry. The wind streaming into this storm was borderline severe, shaking the car and snapping tree branches. It was also blowing an insane amount of corn husks lol. Couldn't even open the car window to shoot without getting a face full of dust, so I shot this through the windshield. Had to resort to longer exposures now that there was hardly any light left. The amount of dust blowing across the road looked like thick fog.



We eventually stopped to shoot the storm once we were out of the insane inflow winds. It started dropping an impressive number of CGs back by the RFD cut/core. Could barely make out the storm's striations visually, but they came out pretty well in images whenever you could get a bright bolt to illuminate the structure.










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