Thursday, June 2, 2011

Wind and Wuthering

Last Tuesday, returning to work after a long weekend, I took a fleeting look at the weather online at around ten to see what might be happening an hour later when I went for my daily walk. At the beginning of the day there was a low percentage chance of rain and a fleeting sprinkle, and at ten it was cloudy outside. On's hourly view, 11 a.m. and later showed a 10% chance of rain, and the doppler animation showed a typical northeastern-moving system decaying on its westerly edge. I went on about my work business.

Around 45 minutes later, coming back from the bathroom, a guy with a sardonic style said "ready for your walk?" - meaning, I discovered as I looked out the window, "ready to get wet?" A steady rain was falling, and when I checked again, noon showed a 25% chance of rain, and the doppler showed what was a former decay area backfilling with green. I thought immediately of the book I was finishing, Last King of Scotland author Giles Foden's book called Turbulence.

About this date in 1944, the top weather wonks in four countries were frantically crunching numbers on the weather data gathered over the prior week. All were trying to get a read on what the weather might be like on a likely major invasion date, a time propitious due to a combination of abundant war material in the vicinity of France, a full moon, and a low tide. Though the predictions for early June two weeks before called for moderate weather, late May's forecast had a big downturn, and Operation Overlord faced a major, sustained storm during that otherwise preferred period. Turbulence is a novel, based on that couple of weeks, which describes the tensions of the relationship between General Eisenhower and the fractious team of forecasters reporting to him hailing from England, the U.S., and Denmark.

Then, as now, weather balloons and toaster-sized transmitters called radiosondes were used for upper-atmosphere readings, and buoys and land-based stations were used for surface data. Reconaissance flights filled in some data gaps in between, but the risks inherent in that gathering mechanism left plenty of holes. After the 1920's, there was much knowledge of how to create formulas relating to the turbulence of storms to at least theoretically increase accuracy, thanks to the research of a mathematician named Lewis Richardson, however,

Richardson’s estimated number of human calculators needed to keep
pace with weather developments was 64,000, all located in one very large room. 1

Even given the number-crunching limitations, however, forecasters had bad enough news for Ike on the third that the planned date of the fifth was scrapped; a storm like that would have resulted in several times the casualties that actually occurred. However, on the fourth of June, all the forecasters came to a rare agreement that there was roughly a day of calm in the action, a day of calm, moreover, which the German forecasters did not see, or perhaps even look for - and that day was the sixth of June. And even though the day featured far from perfect weather, the relative calm made for what all acknowledge as a successful invasion.

Ironically, the satellite data, profusion of ground stations, and especially computers, would not have changed that decision significantly, other than to supply the data slightly more quickly, given the volatility of the system. Of course, the Germans in that case would have had the same data, and would have been much better prepared.

In my case, I went out an hour later and got slightly less wet.

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