Are multi-seasonal forecasts of atmospheric rivers possible?

Forecasts initialized in April have strong prediction skill for January-March atmospheric river (AR) activity on the US West Coast. Credit: NOAA GFDL

Kai-Chih Tseng, Nathaniel C. Johnson, Sarah B. Kapnick, Thomas L. Delworth, Feiyu Lu, William Cooke, Andrew T. Wittenberg, Anthony J. Rosati, Liping Zhang, Colleen McHugh, Xiaosong Yang, Matt Harrison, Fanrong Zeng, Gan Zhang, Hiroyuki Murakami, Mitchell Bushuk, Liwei Jia. Geophysical Research Letters. DOI: 10.1029/2021GL094000

In Western North America, 30% of the annual precipitation is determined by atmospheric rivers (ARs) that occur during less than 15% of the winter season. ARs are beneficial to water supply but can also produce extreme precipitation hazards when making landfall. Consequently, ARs exert significant socioeconomic impacts on this region.

The authors used GFDL’s new SPEAR seasonal-to-decadal forecast system to produce multi-seasonal AR frequency forecasts with predictive skill at least 9 months in advance. Additional analysis explores the dominant predictability sources and challenges for multi-seasonal AR prediction. Regional dependence of atmospheric river prediction can be explained by its connection to the leading pattern of large-scale atmospheric variability over the North Pacific.

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