Optimal Climate Normals for North Atlantic Hurricane Activity

Abstract

AbstractMost climatologies use 30‐year epochs that are updated at the start of each decade. They will shift from 1981–2010 to 1991–2020 in 2021. North Atlantic hurricane activity has large interdecadal variability that may lead to biases in a 30‐year climatology. A previous inactive hurricane period included 1981–1990, while 2011–2020 is a part of the ongoing active era. As a result, the 1991–2020 normals are more active than the 1981–2010 normals, with the median accumulated cyclone energy increasing by ∼40%. A 50‐year epoch would be more likely to capture a full cycle of multidecadal variability, and this study demonstrates that 50‐year climatologies have historically been better predictors of the subsequent decade's hurricane activity. This paper argues that the 1971–2020 climatology should, therefore, be the baseline for hurricane activity for the next decade with a possible adjustment for the non‐climatic increase in observed short‐lived tropical cyclones.