Climate change: North Atlantic hurricane season starting earlier

The first storms of the North Atlantic hurricane season have been occurring around 5 days per decade earlier since 1979, a paper in Nature Communications suggests. The study also suggests that the first named storm to make US landfall has been trending earlier by approximately 2 days per decade since 1900. These findings are important for better planning and adaptation strategies.

The current definition of the North Atlantic hurricane season was established in 1965, and defines the season as occurring between June and November. Although this captures most of the hurricanes occurring in the region, the season lacks a more precise definition and, recently, several tropical cyclones have developed before 01 June, the official start of the season.

Ryan Truchelut and colleagues used observational data to analyse changes in the onset of Atlantic tropical cyclone activity from 1979–2020 and the onset of landfall risks in the US from 1900–2020. The findings indicate that named storm formations in the North Atlantic are shifting earlier in the year, at a rate exceeding 5 days per decade since 1979. The authors also suggest that the first named storm to make US landfall occurs earlier by around 2 days per decade since 1900. They suggest that this trend towards earlier onset may be linked to warming in the western Atlantic Ocean in spring, which has also shown an increasing trend during the same period.

The authors conclude that their findings indicate that the North Atlantic hurricane season could be empirically defined as starting before 01 June. Additional increases in ocean temperatures may exacerbate the exposure of populated landmasses to tropical cyclones by shifting the onset of their formation earlier, they suggest.