Daily Archives: June 9, 2025

Last Friday was the 81st anniversary of the Allied invasion of Europe that began with the landings on the beaches at Normandy.  The combined land, air, and sea assault of June 6, 1944 remains the largest such event in history.  The success of the invasion was extraordinarily dependent of weather conditions.  More than three months before the invasion, a combined British and American forecasting team began rigorous forecast exercises designed to iron out the physical and logistical kinks of such a coordinated effort.  As June drew near, the nature of this collaboration was still problematic as the two groups employed vastly different methods in fashioning the requisite 3-5 days forecasts – at the time, absolutely primitive in the underlying science as compared to what is possible at such ranges today.  The British were attempting to make such forecasts based upon the understanding of atmospheric dynamics that had grown substantially during the war.  The Americans were employing a method based on a statistically- based search through old weather data for historical analogues that could be used to guide the forecast. Continue reading →