Just wanted to chime in with a few notes about our chase in northwest Iowa. I had some serious gremlins with the dome cam and was really busy driving, but thanks to Mike Boik for getting video and Jenn Brindley for getting the stills from the chase. If you missed Jenn's link above, check out her photos. They are truly amazing:
http://jenniferbrindleyphotography.com/blog/tornado-photos-mapleton-ia-chase-492011
Our intercept on the Mapleton storm was a little unorthodox, but afforded us a very dramatic view of the tornado. We were waiting for the storm to mature and move northeast to us as we sat on highway 141 east of Hornick. The roads west of Mapleton get terribly squirrely, so I had us routed to stay to the north and pick the cell up on the east side of Mapleton where we had a nice grid to work with. The tornado warning came in along with the first tornado report as we were moving east well downstream from the storm. Instead of continuing on to the next good south option, I decided to get us under the RFB as quickly as possible. We did an about face and took county road K64 down through the back end of the storm. We came out on the north side of the horseshoe base/rfd clear slot with a ton of RFD, gustnado, and tornado activity just to our south and 1-2 inch hail falling. I couldn't tell which exactly of those three it was at the time, but seeing the funnel pictures above, it appears that it was probably all three.
We took Co Hwy E16 east to keep up with the storm, which gave way to Bob's road. Miraculously, we were able to hold our position north of the bowing updraft base, just ahead of the hook, and south of the forward flank as the road twisted and turned with deep ruts and loose gravel. We finally made it out in the open about a mile northwest of Mapleton and we're staring right at the back end of this massive debris cloud as it was moving into town. The hook caught us as we stopped to film the tornado, which was distinctly audible. We lost our view in the deluge or rain and hail and continued east, trying to get our view back.
I am not certified at all in any sort of first aid/emergency response, and generally avoid damaged areas like the plague. I'm not trying to be insensitive, its just that I would probably do more harm than good entering a disaster scene, and would probably wind up a victim myself. All roads in the area lead right through Mapleton, so we attempted to drive through it, knowing that we'd more than likely be blocked and find ourselves dealing with massive devastation. Coming into town, we were still in the hook of the storm, and it was extremely chaotic. There was panicky local traffic, including huge farm equipment, barreling in multiple directions which we had to dodge. Leaves and small branches were still flying through the air, and poles were swaying in the RFD. Given the size of the tornado, I had expected much worse damage. What we witnessed was mostly tree damage and some minor building damage. All the structures we passed were still standing though. Given that the town isn't too large, I assumed that, although appearing quite large, the tornado was a weak dusty bowl and had largely spared the town. I had no idea the southwest side of town took the brunt of damage so we continued on in chase mode. We attempted to drive east through town on E16, but there was a large tree down two blocks in. We went south a block and were stopped by another tree, but were able to drive around it and get back up to the highway and heading east again. The storm had moved northeast by then and we were able to get back out ahead of it following along from the south.
The rest of our chase was followed by some of the strongest inflow I've ever experienced on a chase, an amazing lightning display, and several more tornadoes of various shapes sizes from cone, to wedge, to stovepipe, all back lit in the night by lightning. When I fix my desktop, I will post a chase log with more details, pics and video borrowed from Mike and Jenn, and a radar animation and map.
