NOAA predicts more active Atlantic hurricane seasons

Nov. 26 () –

The variability of Atlantic tropical cyclone activity will increase, leading to more active and inactive hurricane seasons and fewer seasons close to normal.

This is the conclusion of a new study published in Science Advances by NOAA (the US climate agency) and associated researchers, focusing on how the frequency and accumulated cyclone energy (ACE) in the North Atlantic could change in the future. ACE is the measure of total seasonal activity used by NOAA scientists to analyze past and future changes in tropical cyclone activity, focusing on changes that occur between two or more years and the impact of a changing climate.

Researchers examine why there have been so many active seasons in recent years. The results show that unusually active and inactive hurricane seasons have become more common since the 1990s, and computer models predict that by the middle of this century, variability could increase by an additional 36%, with the largest increase occurring would occur in the central tropical North Atlantic, which refers to the middle section of the North Atlantic Ocean where tropical storms and hurricanes most frequently form. These changes are related to changes in wind patterns and ocean temperatures.

For a tropical cyclone to form, several atmospheric and oceanic conditions must be met: a pre-existing weather disturbance, warm ocean waters (above 26 degrees Celsius), thunderstorm activity, and low vertical wind shear, which are speed differences. of the wind between the top and bottom of the hurricane. Higher wind shear serves to deter hurricane development.

Changes in vertical wind shear and atmospheric stability (the ability of strong thunderstorms to develop), driven by ocean temperature differences between the Pacific and Atlantic oceans, are responsible for the change in variability. These changes are expected to become more evident in the future, further intensifying variability in Atlantic hurricane seasons. as reported by NOAA in a statement.

“Historical year-to-year variability in hurricane seasons is much greater than any projected future trends in hurricane activity,” Hosmay López, a NOAA oceanographer and lead author of the new study, said in a statement. “While the scientific consensus is that there will be a future reduction of 2 storms per year, the number of named storms in the North Atlantic revealed much larger swings between 28 named storms in 2005 and 8 in 2014. Despite these large fluctuations from year to year, future changes in the interannual variability of hurricane activity are rarely investigated in detail, resulting in significant uncertainty in future projections and impacts. Therefore, there is an urgent need to “better understand not only changes in mean activity but also changes in interannual variability.”

The study also found that while the total number of hurricanes in a given season, averaged over many years, should not change much, the likelihood of extremely active seasons will increase due to a projected increase in year-to-year variations. other. An amplified variation will increase the number of inactive and active seasons at the expense of a reduction in near-normal seasons.

Larger interannual swings between busy hurricane seasons and quiet seasons in the North Atlantic pose significant challenges for forecasters and emergency decision makers. The variability from one season to the next makes it harder for scientists to predict the severity of a given hurricane season.

Additionally, the unpredictability of active and inactive seasons creates challenges for disaster preparedness and response, as some seasons will be extremely dangerous while others will be relatively calm. This means that communities in hurricane-prone areas will need to adapt to seasons that have the potential to be extremely active, as seen in 2005 and 2020.