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Chase Account - Sunday 16th May

From Lincoln, Nebraska - chasing around Wolbach, Nebraska - back to Columbus, Nebraska

Tony Gilbert, Terry Fryer, Sam Jowett and Ali Dibb

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With some anticipation we looked through the morning models today expecting to find some strong potential.  This we did but there were big concerns over the amount of clear sky available to kick start deep convection... assuming any could initiate it seemed apparent that strong supercells/MCS with tornadoes and large hail would be likely, so today became a day of chase the clear slot and wait for it to fill in.

We initially headed N to Norfolk where models had indicated strong potential but were greeted by rather more cloud cover than we were happy with.  Having spoken with other chase teams further S we discovered we'd misplaced ourselves with regards any clear air so we punched back S again meeting a small thunderstorm near the village of Newman Grove which we briefly diverted to.

Having pulled down some more data we decided to continue SW towards cells that were firing over Dawson county.  There was a line of storms along the frontal zone, one of which we had just encountered, but as ever, the southern storms were the best.  We planned to try and intercept over Sherman county but realised that road options would mean that would take too long and instead chose to park up at a good viewpoint just N of St Paul.

Developing storms to the N were already crossing this area which allowed me to get the 3 images on the right.  The funnels could barely be categorised as such as their rotation was so weak, but these were under updraught regions and demonstrated the potential.

Meanwhile to the S, the storms had become more organised and tornado warned... we needed to position ourselves so that we could try and intercept the core as they moved NE.

Convection

Funnel

Funnel

All this meant in reality was actually moving a few miles further N again and we chose a spot a few miles W of Wolbach, Nebraska where we could get a good viewpoint and have useful road options in case the tornadic core passed over head.  As we would be on the wet side of the storm some careful sky watching and positioning would be needed...

These next couple of images demonstrate some of the dynamics of the gust front.  A quite tidy roping out funnel can be seen above and beyond the van in the first picture (remember you can click on it for a larger view) and the fingers of scud in the following picture nicely demonstrate how much this boundary swirls and moves.

Funnel

Turbulence

After holding fire for a little longer the precipitation curtain from the anvil of the dominant cell to the S started to invade our position.  Being well aware this was tornado warned and that we wanted to maintain as much visibility as possible, without moving too far away, we jogged E a few miles towards Wolbach.

Supercell

Supercell

This jogging backwards and forwards continued a couple of times, trying to maintain a discrete distance whilst not missing the action, but eventually we actually ended up to the E of Wolbach which had by now become tornado warned itself.  Unfortunately the whole system seemed to be completely rain wrapped from our position and despite seeing some quite rapid rotation in updraught regions above us a few times (enough to persuade us to punch E in the van with haste at one point), we didn't see any tornado.

I'm not sure if there was actually one on the ground as it crossed this area, despite it being radar indicated, but there were unidentifiable lowerings in the cloud base amongst the rain.... perhaps we were just a bit too timid.  We were treated to a nice sunset as the southerly cloud base started to clear though...

Supercell

Shelf Cloud

Precip Core

Daytime Darkness

Supercell

Sunset

And some video footage of the cloud motion and funnels we witnessed. (To view locally, right click the links and choose Save Target As)

An attempt at a funnel on a developing updraught - 7.5MB

Cloud Motion - 11.5MB

Funnels or tornadoes? - 26.5MB

Wall Cloud - 41.7MB

Route