Des Moines Airport Tornado November 11th 2015

Nov 12, 2015

Summary:

Difficult chase playing tag with QLCS style rotations embedded within numerous storms. Managed to capture weak tornado touching down at the DSM airport.

Stats:

Tornadoes: 1
Hail: .50″ (dime)
Wind: Est 60-70 RFD

The Setup:

Strong, deepening mid latitude cyclone bringing extreme values of shear across the midwest. Just in time nature of moisture return was a big concern, and forecast CAPE values were low. This lead to question as to how real the tornado potential would be, but with shear nearly off the charts, and it being a midwest event, it was foolish not to chase. SPC went with 5% tornado probabilities due to the low values of instability, otherwise this would have been high risk worthy.

Detailed Account:

It appeared fall 2015 was going to be chase-less, however this setup began popping up on the forecast models almost 2 weeks out. To our surprise it only wavered a little bit and by the time the day came, a chase was warranted. It appeared initiation could take place as early as 10am so I left Chicago about 3am to get out there early. On the way I scooped up Alec Scholten, and then later rendezvoused with others near Creston, IA which was where I wanted to play the waiting game.

We milled about at a rest stop until storms finally began firing, it was going to be a difficult chase with numerous storms, picking the right one was basically a dart throw. Storms had fired by noon but nothing we wanted to go after. Slow intensification was occurring and we finally had our first tornado warning in southeast Nebraska with new development occurring about half an hour to our west. We decided to move into position. As expected cells were numerous and close together. We let the first couple go by as they appeared weak and unimpressive. Then a stronger cell began approaching and we moved north to get into position.

Storm speeds were very fast, 55+ mph so we wanted to be well downstream. I was the lead vehicle in a 4-5 car convoy most of the chase, I pulled over on a side road that ended up having no real shoulder to watch the storm approach. Structure wasn’t overly impressive, but rotation was evident at the base.
IAstorm11115

The storm passed us with some swirling rain bands and intense RFD/Straight line winds on the backside, probably pushing 60-70mph. We moved north after it, passing sporadic tree damage along the way. By now other storms to the south were intensifying and gaining tornado warnings and the event was well underway. This storm slipped away to the north after we got caught by slow moving traffic in Atlantic, IA. Storms took on a linear appearance but had embedded circulations within them. We decided to head to I-80 where we would hopefully be able to blast ahead and then drop south to hopefully find a circulation or tornado.

Blasting through the line proved more difficult than we hoped due to the high rate of speed and slow moving traffic, but we eventually made it through just west of Des Moines when a pair of tornado warnings was issued to our south. We bailed off the highway where we got into position, sirens wailing. Visible cloud rotation passed nearly overhead and we noted a windshift with some tree debris flying around but it was hard to confirm anything tornadic actually on the ground. We dropped east and south again to a new couplet. Here we had a much better visual of a large rotating meso. Of course, Iowa throws us a curveball and suddenly our highway has a large hill on it obscuring our ground view, but I can see a sharp left edge with chaotic swirling motion. I’ve seen this before….

Up ahead the exit ramp appeared to provide a clear view to the south so we once again bailed off the highway, the storm was definitely rotating in the low levels. It passed overhead and became obscured by a new hill, and thats when a funnel dipped down.
Des Moines Tornado

A likely tornado had just touched down. The funnel quickly dissipated but the rotation persisted and a new funnel formed, stretching about halfway down. We jumped back in our cars to pursue the developing tornado. Storm speed and road direction didn’t work out in our favor though as the storm rocketed away to our north and our road dipped southeast. The tornado ended up doing minor damage at the airport though and was soon confirmed by the ASOS. We could see the rotation on the backside as there was rapid clearing behind the line of storms.

We decided to do what we did before, get back on 80 and blast through the line again. The sun was beginning to set now, and the backside was lit up nicely.
IAstorm11115-2

We wound up in one more wrapped up circulation with chaotic motions, but again it was hard to confirm anything tornadic on the ground. A few dramatic windshifts would suggest we got hit by some sort of circulations, though. As darkness began to set in we let the storms go and called the chase. It was not worth such a pursuit in the dark, for what would likely be limited, low contrast views of any tornadoes. We grabbed dinner at a Perkins in Iowa City, parted ways and headed home. The chase was over by 5pm and I was home at 1030pm.

Conclusion:

Through our blood sweat and tears, we were able to catch at least one tornado. On a late season chase this difficult, it was a nice victory. Turns out there were numerous tornadoes, a few of them actually being somewhat photogenic. Few chasers caught any though, and the best shots came from locals. There was no way to know which storms would produce and much of the day relied on luck. In the end it was nice to be chasing again, getting into some wicked weather and documenting a tornado, albeit a weak, low contrast one.

Video:

Map. Arrow shows location tornado was filmed:

11-11map

Tornado Info:
Capture1

SPC Reports:

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