Day 19 - Bluffing Squares

22 June 2010

Today started in our home away from home: Sterling, Colorado. For people with few navigational skills we do know this area quite well now. We know where Walmart and a good motel are anyway. The models were pointing to this being a good area, though things looked a little more promising further north. We headed up to Sidney to find our favourite park where there's a wireless hotspot and some tables to have some lunch and look at radar, satellite imagery and, of course the skies!After a couple of hours it looked like some action was happening a little further north, near Scottsbluff (again). We began a familiar journey there, including the drive through Bridgeport. I think that place will always hold some of the strongest storm memories for both of us, having been the town where we witnessed our first big storm, driving away through the roaring winds and tornado sirens.We saw our cell and got in close. It was looking pretty healthy. We positioned a little in front of it, and saw a good wall cloud descending, even seeing it trying to put down a tornado.

After some time deciding whether to follow it in case it found its legs again, or go after a new one that was (quite weakly) showing signs of doing something. We had to balance that with the fact we needed to be a few hundred miles away for tomorrow. Best to make ground, so off we set.A few miles down the road and we had some spectacular views of a random new cell firing to our south. It was showing all the ingredients of being a good one, and what's a 50 mile diversion on a drive like the one ahead? So we dived south. It was now tornado warned too! Sadly we were in such a rush to get on it, we didn't stop to take pictures of its incredible towering structure in the dusk sky. I say sadly, because when we got in range it had also lost its legs and was dissipating. And it was mostly dark. But we did get our fill of a good lightning display.We pushed on for Missouri, stopping in central Nebraska when we got tired. Maybe the outlook would be closer in the morning!Addendum - educational bit - why did the cells die?It's not common for cells to die like they did, after reaching the stage they did. The ingredients were all there. We asked some people in the know, and the answer was all back to do with the capping. To recap (if you'll excuse the pun, or even if you won't, because I'm writing it) - capping is where temperatures aloft are higher than they should be, given that temperatures should drop at a consistent rate as you get higher (called a lapse rate - normally 6.49C per 1000m). This can inhibit air rising above it, so called capping, stopping storms firing. In this case the cap HAD been broken in Wyoming, just over the border from Nebraska where we first saw the cell. It had broken as air pushed over the hills there, forcing it upwards through the cap, and up went the storm. As the storm started moving into Nebraska it lost this forcing from the hills and the cap was stronger in Nebraska. Strong enough, in fact, to choke the updraft of these storms. Once the updraft loses power, the storm just starts, quite literally, falling out of the sky. This probably explains the sudden and wide area of rain we experienced. The storm can continue for some time with the power it already has, but its fate is inevitable once the updraft is gone.

SPC Day 1 Weather Outlook as at 06:00UTC (01:00 Central Time the night before)

SPC 01:00UTC day 1 forecast for Tue June 2010

SPC Day 1 Weather Reports for the day.

SPC storm reports for Tue June 2010

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