The Influence of Climate Variability and Future Climate Change on Atlantic Hurricane Season Length
In recent decades, North Atlantic tropical cyclones (TCs) have been observed well before and after the official hurricane season. We investigated oceanic sources of predictability in Atlantic hurricane season length, start, and end using historical observations. We found that a warm western subtropical Atlantic ocean in boreal spring drives early hurricane season starts and La Niña events in autumn drive late season ends. In addition, we investigated future changes in Atlantic hurricane season length using the Energy Exascale Earth System Model (E3SM). E3SM projected an increase in hurricane season length of 27 days under La Niña and positive Atlantic Meridional Mode (AMM) conditions and 41 days under neutral El Niño – Southern Oscillation and AMM conditions.
Projected future increases in Atlantic hurricane season length, together with future increases in Atlantic TC number and intensity, indicate the potential for exacerbated Atlantic TC impacts in the future arising from more frequent and intense TCs occurring over an extended hurricane season.
Atlantic hurricane season length is important for emergency management preparation, motivating the need to understand its variability and change. We investigated the influence of ocean variability on Atlantic hurricane season length in observations and a future climate simulated by the Energy Exascale Earth System Model (E3SM). We found that multiple factors influence hurricane season length, through their influence on season start and end. Warm western subtropical Atlantic sea-surface temperature anomalies (SSTAs) during boreal spring (before the official hurricane season start) drive early starts to the hurricane season, and vice versa for cool SSTAs. Meanwhile, La Niña in autumn (before the official hurricane season end) drives late ends to the hurricane season, and vice versa for El Niño. E3SM projects a 27-day increase in future Atlantic hurricane season length given La Niña and warm northern tropical Atlantic SSTAs. This research documents sources of predictability for Atlantic hurricane season length.