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Three western pacific typhoons strengthened fire weather in the recent conflagration in northwest U.S.
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  • Shih-Yu (Simon) Wang,
  • Jacob Stuivenvolt Allen,
  • Matthew LaPlante,
  • Jinho Yoon
Shih-Yu (Simon) Wang
Utah State University

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Jacob Stuivenvolt Allen
Utah State University
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Matthew LaPlante
Utah State Univeristy
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Jinho Yoon
Gwangju Institute of Science and Technology
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A heatwave and fire outbreak in the western United States in early September of 2020 resulted from an atmospheric wave train that spanned the Pacific Ocean basin. Days before the atmospheric waves developed in the U.S., three western Pacific tropical cyclones underwent an extratropical transition within an unprecedentedly short span of 12 days. Using a climate diagnostic approach and historical forecast data from the Global Ensemble Forecast System (GEFS), it was found that the amplitude of the atmospheric waves accompanying the western U.S. fire weather would have been reduced if not for the influence of these cyclones. Together, the recurving typhoons provided a significant source of Rossby wave activity toward North America-amplifying the ridge over the U.S. west coast while deepening the trough in central Canada. This anomalous circulation was a precursor to the severe frontal system that caused extreme winds in western Oregon-starting and rapidly spreading fire.