Lewis and Clarks’ Tempest: The ‘perfect storm’ of November 1805,Oregon,USA

Three weeks after arriving near the Pacific Northwest (PNW) coast in November 1805, Lewis and Clarks’ Corps of Discovery experienced a two-day windstorm that may have rivaled the strongest historically documented storms of the nineteenth and twentieth centuries. Based on the Corps’ detailed historical accounts describing the event as the perfect storm, we characterized the severity of the 1805 windstorm using tree-ring growth anomalies from windsnapped Sitka spruce collected at three sites along the northern Oregon Coast. We compared the 1805 gale to eight other documented events with comparable storm tracks and exceptional magnitude including the 1880 and 1951 events that each caused more than a billion board feet (c. 2.4 million m³) of windthrow. Statistical comparison of tree-growth responses revealed that the 1805 windstorm was the only event to differ significantly (χ²; test, p < 0.05, d.f. = 1) from all other storms. Our findings demonstrate the potential application of tree-ring data and historical documents to understand previously obscure climatic events similar to the extreme droughts that led to the demise of the Roanoke Colony during the sixteenth century and adversity experienced by the Jamestown Colony during the seventeenth century. Specifically, we identify the Lewis and Clark tempest of 1805 as being among the most severe PNW windstorms during the past two centuries, and may have contributed to the Corps’ dismal view of coastal Pacific Northwest weather.