Friday, June 26, 2015

6/21/2015 Lodgepole to Bison, SD Tornadoes

6-21 was a great storm observation day in northwest South Dakota.  The morning observations/satellite imagery led me to paint this target:
Morning tornado forecast (X indicates my forecast for convective initiation)
Fortuitously, convection developed just a few miles west of our target, and tracked southeasterly with the steering winds:

We waited in Marmarth, ND for the maturing convection due to the poor road network and we did not anticipate tornadogenesis until the storm reached the better 850 hPa moisture and winds. We did get to see some cool Kelvin-Helmholtz instability waves while waiting for the storm to approach.
KH Waves
As *soon* as that storm reached the better moisture, it went on to produce 4 tornadoes (one a large dusty bowl shape) from Lodgepole to Bison, SD. I think we played the storm just right with regards to the road network, and were handsomely rewarded with some great stills, lapse, and video.  We put the cherry on top by photographing decaying Cb and associated lightning in the twilight. Certainly one of the best chase days of 2015! 
Initial supercell
Tornado # 1
Ropeout of tornado # 1
Tornado #2
Recycle after tornado # 2
Tornado # 3
Continuation of tornado # 3
Tornado # 4
Letting the cell drift away (looking east)

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