Patterns abound in nature. The rings in a tree stump, the spots on a leopard, the ripples in a pond all speak to patterns. Weather has patterns. Weather patterns are the recurring behaviors of the atmosphere in a region over time, showing predictable trends in temperature, precipitation, wind, and pressure. Weather patterns describe how the atmosphere behaves over weeks, months, or even years. They are, however, not forecasters of daily weather, which can change rapidly.
“Pressure” was the name of a film I saw recently. It’s a slightly fictionalized tale of weather events leading up to D-Day, June 6, 1944, the Normandy invasion given the Code names Operation Neptune and Operation Overlord. The story centers on the weather forecast for June 5, 1944, Major General Eisenhower’s chosen day.
The invasion planners had determined a set of conditions involving the phase of the moon, the tides, and the time of day that would be optimum for an invasion using over a million troops. A full moon was desirable, as it would provide illumination for aircraft pilots and have the highest tides. The Allies wanted to schedule the landings for shortly before dawn, midway between low and high tide, with the tide coming in. This would improve the visibility of obstacles on the beach while minimizing the amount of time the men would be exposed on the open beach.
The two primary meteorologists disagree on the prediction for June 5th. Group Captain James Stagg is the Supreme Headquarters Allied Expeditionary Force (SHAEF)’s Chief Meteorologist Officer. His adversary is US Col. Krick. Krick fully believes in the historical weather patterns for June 5th throughout decades that show a bright sunny day. Stagg violently disputes the use of the historical data and instead relies totally on incoming and up-to-date reports from the field. His weather intelligence, sent in from a weather station on the western coast of Ireland, indicates a storm brewing in the Azores which would bring heavy rains and high seas to the Channel on June 5th.
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Surface weather analysis map showing weather fronts |
Eisenhower reluctantly postponed D-Day to June 6, and Stagg is proved right when heavy rains sweep the area, there are high and turbulent seas in the Channel, and the cloud cover prevents aircraft from flying. Stagg further predicts a break on June 6th.
The rest is, in fact, history. That history proves the point that weather patterns are excellent historical records that have a place in forecasting.
Stephanie Booth
