Three Western Pacific Typhoons Strengthened Fire Weather in the Recent Northwest US Conflagration

Strong winds that accentuated a fire outbreak in the western United States in early September of 2020 resulted from an atmospheric wave train that spanned the Pacific Ocean. Days before the atmospheric waves developed in the United States, three western Pacific tropical cyclones (typhoons) underwent an extratropical transition over Korea within an unprecedentedly short span of 12 days. Using a climate diagnostic approach and historical forecast data, it was found that the amplitude of the atmospheric waves accompanying the western U.S. fire weather would not have been so profound if not for the influence of these typhoons. Together, the recurving typhoons provided a significant source of wave activity flux directed toward North America - amplifying the ridge over the U.S. west coast while deepening the trough in central Canada. This anomalous circulation produced the severe frontal system that caused extreme winds in western Oregon, Washington and California - rapidly spreading fire.

Automated summary

Strong winds that exacerbated a wildfire outbreak in western United States in early September 2020 were caused by an atmospheric wave train spanning the Pacific Ocean, influenced by three western Pacific tropical cyclones. Together, these typhoons provided significant wave activity flux directed towards North America, amplifying weather patterns and intensifying the frontal system that spread the fires rapidly.