This study investigates the influence of the boreal summer intraseasonal oscillation (BSISO) on heat extremes and wildfire risks in the Pacific Northwest (PNW). The research reveals that during BSISO phases 6-7, the likelihood of heat extremes and fire-conducive weather conditions in the PNW increases significantly (by ~50-120%). This is primarily attributed to enhanced diabatic heating over the tropical central-to-eastern North Pacific, generating a downstream wave train that results in a high-pressure system over the PNW. This system promotes surface warming through increased surface radiative heating and enhanced adiabatic warming. The findings suggest a pathway for improving subseasonal-to-seasonal predictions of heatwaves and wildfire risks in the PNW by better representing BSISO heating in climate models.

Sandro W. Lubis, Ziming Chen, Jian Lu, Samson Hagos, Chuan-Chieh Chang, L. Ruby Leung