Nov 11th, SW Iowa

Initial Target: Creston, IA
Storm Intercepts: Osceola, IA
Features: Bowl funnel
States: Iowa

Miles: 275

Summary: Cold front, high shear, late season chase

A November chase in Iowa?? Not completely unheard of, but still unusual.

This was one of those weird setups with INSANE shear, but little/marginal CAPE.

I met up with fellow chaser Andrew Clope from Peoria, IL at the Subway in Osceola IA, where we reviewed forecast data for a few hours. We decided to head to Creston and then take a look at HRRR and surface observations. A tornado watch had just been issued for the region. We wanted to be closer to the surface low centered near the Iowa/Nebraska/Missouri border, but were hanging on to the belief that any storms which fired there would move into SW Iowa where they would mature in the better-sheared environment. The HRRR model runs were showing the system rapidly turning into a squall line (which it did) and with 60+ kt winds pushing this system we would only have one chance to pick an isolated cell (if one could even remain isolated) to chase. We saw a lot of well-respected chasers in our general area, which added some assurance to our forecast.

In Creston, we pulled into a gas station and saw Brennan Jontz and Zach Sharpe from the Iowa Storm Chasing Network hanging out there doing a livecast so I said a quick hello and did about 15 seconds of guest video.  Adam Lucio was also parked off to the side, and by his presence confirmed our forecast location :). 30 minutes later we all split up and Andrew and I headed to a field south of Corning, IA. Storms began firing in Nebraska, and one went tornado warned. A friend of ours was on that cell and sent pics. Because of low LCL and 2 degree DP/DT spread, it was basically a tornado embedded in fog and very difficult to see. The system started to line out nearly immediately (as crashing cold fronts tend to do) so it was decision time. We picked what looked like a healthy cell in Missouri and waited for it come to us. It arrived for intercept at a very quick pace, just as we got back to Osceola. We had parked at a good vantage point to watch it, but it was moving FAST. We were able to make out the system base, and then saw a large bowl-shaped funnel, rotating slowly. This had already been reported as a tornado, so Osceola sirens were going off. This was a messy system and didn’t have a rain-free base, making visibility (and pictures/video) difficult. Andrew shot video from inside his truck; I didn’t bother getting my camera out. Heavy wind and rain came upon us within seconds, so we sheltered our vehicles on the NE side of a nearby hotel.

After it went overhead, we both headed back to our respective homes. In the 55 minutes it took me to drive from Osceola to Altoona, the system had accelerated and had gone through the Des Moines area 20 minutes before my arrival.  

A pathetic chase, but still fun to keep our forecasting skills honed months after chase season 2015 ended.