Too Early to think about the Tropics ?

 

Hurricane Ian making landfall in 2022 (Source: WUSA9)

NOAA recently announced that while a weak episode of La Nina remains present, ENSO (El Nino Southern Oscillation) neutral conditions are expected to develop over the next couple of months.  “ENSO-neutral conditions” simply refers to the absence of El Nino or La Nina conditions.  While impacts from El Nino or La Nina have heightened significance in the United States during the winter months, they can also impact the Atlantic hurricane season.

On February 9, NOAA said: “There are increasing chances of El Niño at longer forecast horizons…”  The time frame for that would be later in the summer and early fall.  El Nino conditions, particularly moderate to strong El Nino’s, create less favorable conditions for hurricane development in the tropical Atlantic.  Such conditions include cooler sea surface temperatures, combined with an increased amount of wind shear (winds that change direction with altitude). 

However, five of the last six summers have featured weak to moderate intensity La Nina’s.  Consequently, four of the last six years have seen active Atlantic hurricane seasons.  An exception was last season that finished with an average number of Atlantic tropical storms and hurricanes, the majority of which were weaker, more short-lived systems that combined to create the lowest ACE score for an Atlantic hurricane season since 2015.

Some may recall that the last very strong El Nino developed in 2015 and it was a significant contributor to the last below average Atlantic hurricane season.  Of course, there are other factors that play a role in how active an Atlantic hurricane season is such as the status of the North Atlantic Oscillation (NAO) and the amount of dust present in the atmosphere that blows from Africa’s West Coast into the tropical Atlantic.  High concentrations of atmospheric dust tend to preclude widespread tropical development.

If climate experts at NOAA expect an episode of El Nino to develop during the middle or second half of the Atlantic hurricane season, then that could impact seasonal hurricane forecasts.  Since at least one named storm has developed prior to the official June 1 start of the season in seven of the last eight years, it isn’t too early to start talking about the upcoming season.

It’s also important to not lose sight of the fact that all tropical storms and hurricanes are potentially dangerous, even during a quieter than average hurricane season.  Hurricane Alicia (1983) and Hurricane Andrew (1992) were each the only major hurricanes of their below average seasons, but both rank among the most destructive U.S. hurricanes of their respective decades.