One significant effect of the stronger El Niño is fewer hurricanes in the Atlantic. In the 30 years to 2020, on average the first hurricane arrived by 11 August, the second by 26 August and the third by 7 September. This year the total so far has been zero.
At the start of the season, the National Oceanic and Atmospheric Administration (NOAA) predicted a quiet year, anticipating between three and six hurricanes, well below the average of seven. The August forecast cut the expected number to between two and six. Until this year, the latest date for the first Atlantic hurricane was 11 September, in 2002 and 2013.
El Niño is marked by comparatively warm sea surface temperatures in the Pacific and a weakening of the seasonal trade winds. One side-effect is that it increases wind shear – the change in wind speed with height – over the Atlantic. This makes it less likely for tropical storms to evolve into hurricanes, as these require relatively stable air to form over a wide area.
But while things have been quiet on the Atlantic side of the Americas, the eastern Pacific has seen plenty of activity, with seven hurricanes so far. The energy added by a strong El Niño may also produce more powerful tropical storms later on.
