COMPLEX ADAPTIVE SYSTEMS DOING WHAT THEY DO.

The past few days have brought some interesting weather to Cold Spring Shops headquarters.  A major storm system has been crossing the United States, and on Friday night there were squall lines doing what they do from the Cities all the way to the Gulf Coast.  The line was still strong enough after dark that the storm prediction folks essentially issued a tornado warning along a line from Aurora to Elgin moving east into Chicago.

The consensus forecast was blustery with a risk of severe thunderstorms on Friday, strong winds but no rain or snow on Saturday, and a dusting of snow on Sunday.  Extrapolation models have margins of error.

That's the "dusting" of snow at Cold Spring Shops headquarters on Sunday morning. To the north, Rockford and Belvidere were reporting heavy snow, and it continued for some time east to Marengo and essentially all along Interstate 43 into the southwest suburbs of Milwaukee, with several roads closed account crashes in white-out conditions, and a few neighborhoods reported six inches of snow, which might have been the most snow received in one storm all winter.  None of the forecast models could parse the atmosphere finely enough to capture the locally energetic snow squalls.  "It's a non-trivial avoidable error: are there no tornadoes, one tornado, or several tornadoes in two counties of Iowa, which is one way of thinking about a cell a hundred kilometers on a side and however high the atmosphere is?"  (The area I described is slightly smaller than that 10K km² cell in a forecast model.)

By Monday, the clouds had cleared and the just-past full moon had an opportunity to give that luster of midday until sunrise.

The snow has since melted away, except in the more shaded areas.  This being the time for the equinox, the unsettled weather will continue, with warmth on offer Tuesday and another risk of snow Wednesday into Thursday.