February 10, 2013


Initial Target
Storm Intercepts
Ottumwa, IA
Springfield, IL 7:41 AM 2/10/2013
Springfield, IL 8:23 PM 2/10/2013
0 mph


Early season cold core setup in southeast Iowa. Targeted nose of narrow warm sector by Ottumwa, IA where low level instability was forecast to be greatest and modest dewpoints in the mid 40's pooled under cut off low with -35C temps at 500mb. Despite steep low level lapse rates, and lines of cumulus developing under clear slot, storms failed to initiate. Dinner with Nolte, Goddard, and Irvin before driving home under a pretty sunset.

Crew and Equipment

Solo chase. Equipment: Canon 60D, Canon t2i, Canon EFS 10-22, Canon EF 50mm.




My first storm chasing journey of 2013 was not a highly anticipated event. It wasn't an event at all. I feel like I have to explain myself as to why I even chased this day, so I'm starting this log with a few of the parameters that I was watching beforehand. This chase was an extreme long shot, but I felt it had some modest potential, was close enough to home, and proved to be a good equipment test before things really heated up. The plot on the right shows the low level instability forecast over Iowa a few days before the event. With dewpoints in the mid to upper 40's, normally way to low for a supercell or tornado chase, and cold air aloft pooling under a cut off low, the low level instability plots were spiking. The pattern looked like a textbook "cold core" setup, which can produce tornadoes with subpar parameters, although the dewpoints and instability were still low even for a cold core event. Still, the models indicated modest surface based CAPE of 500-1000 J/kg, and very favorable shear profiles with a warm front draped across southern Iowa.
The 500mb chart showed a screaming 100 knot midlevel jet. I was hoping the dynamic forcing it would provide might compensate a bit for the lack of instability with this setup. Another concern, however, was that the shear would overwhelm the low topped convection and tear it to pieces before it could develop a sustained mesocyclone.
Another favorable plot that I was watching was the 700mb relative humidity, which showed a pronounced clear slot pushing in behind the warm sector. The drier air aloft would clear out the low level clouds in the morning and allow for solar heating and destabilization of the atmosphere. It was exactly the kind of plot we wanted to see for this cold core setup.
SPC didn't even give the cold core end of the event a mention or glance. All eyes were focused on Dixie Alley were a more classic and significant southern style severe weather event was forecast, with the possibility of strong tornadoes mentioned. I don't chase Dixie Alley, it's too far of a drive for miserable chase terrain and what often winds up being ground scraping, ugly, grungy storms, and HP supercells with rain wrapped tornadoes. The cold core was right on my doorstep (sort of) and I was itching to get out there after a long winter. Despite everyone saying the cold core was going to be a non event, the forecast models continued to show a modest chance at low topped convection with the possible of some mini supercells (at least that's how I interpreted them). The morning model run of the RAP looked great, showing modest moisture in place, clear slot wrapping in from the KC area, and the visible satellite showed clearing about to overtake the warm sector as well. Everything appeared to be in place for a cold core event, so I left Springfield early in the morning and made for my preliminary target of Ottumwa, IA.

Time Lapsing Pancake Cumulus
2 mile W of Ottumwa, IA
2:39 PM
I arrived just before noon with temps in the low 50's and dew's in the mid 40's and stiff southerly wind. A cumulus field was moving northeast overhead, and I hoped that as instability increased in the warm sector, the cumulus would take off into towers and low topped storms. I was tinkering with the Canon 60D shooting some time lapse of the clouds racing past. Nick Nolte soon joined me, while Brad Goddard and Jodi Irvin waited in the next town over. We all waited, watching the rows of cumulus go past for several hours. Cold core setups normally peak in the early afternoon when the solar heating is maximized. The cumulus seemed to line up into a nice line along the cold front and we hoped we'd have initiation. The line came and went, however, and all we saw were pancake cumulus. There was no vertical growth. Surface winds eventually started to veer as the cold front approached, and the sun was getting low. By about 4pm we called the chase a bust. Goddard, Nolte, Irvin, and I converged at a little pub in the next town over to get some dinner and hang out for a bit before splitting up.

Donnellson, IA
5:45 PM
I ran the DSLR in a video time lapse mode on the way home playing with low FPS settings to maximize low light performance. It worked quite well and I was treated to a pretty sunset. While the chase was a bust, learning these new techniques and practicing the workflow with the camera would be valuable for the real deal chases later in the season.
I was home by about 8:30 and burned almost 500 miles on the van chasing pancake cumulus. The southern end of the setup did indeed verify with several tornadoes raking Mississippi and Alabama. An EF4 struck Hattiesburg, inflicting severe damage and casualties. Storm Assist was able to provide some aid to a local animal hospital.


My first chase of the year was a dud that I should have skipped, but I don't regret having made my own forecast and running with it, even if it did bust. Still it was good to test the equipment for the 2013 and try out some new techniques with the camera such DSLR video and time lapsing. I thought the conditions were there for a possible cold air funnel/tornado and went against the rest of the forecasters and common sense about what parameters are necessary. I believe a lack of convergence and a well defined boundary at the surface, in addition to the insufficient moisture, is what ultimately did this setup in. SPC's mesoanalysis plots also did not line up with what the NAM and RAP had showed leading up to the event. 3km Cape values were well below the originally forecast values as was SBCAPE. It seemed the coldest air aloft was not aligned with modest moisture and heating at the surface.

Lessons Learned

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