Activity by ENSO and SST

Two key factors that play a significant role in shaping the frequency and intensity of Atlantic hurricanes are the sea surface temperatures (SST) in the Atlantic main development region (MDR) and the state of the El Niño Southern Oscillation (ENSO). Typically, warmer sea surface temperatures serve as a catalyst for increased hurricane activity. On the ENSO front, positive phases, commonly referred to as El Niño, tend to dampen hurricane activity, whereas negative phases, known as La Niña, often fuel more active seasons.

The animation charts each year from 1950 as a function of ENSO state and SST in the hurricane main development region. The visualization scales each year to be proportional to that year’s level of activity within the Atlantic basin. Years that are characterized by lower SST and a higher ENSO index appear in the animation’s bottom right and tend to be smaller, i.e. have lower activity. Conversely, years marked by higher SST and a lower ENSO index, positioned in the top left, show heightened activity. 2023 stands out for its exceptionally high SST and high activity given its ENSO state.

As we look forward to the 2024 hurricane season, which is only a few months away, the current forecasts for the ENSO during the late summer – coinciding with the peak of the hurricane season – indicate the likelihood of a La Niña event: average model prediction is suggesting an ENSO index around -1. Although forecasts for Atlantic Sea Surface Temperatures (SSTs) do not extend to late summer at this time, the existing SST measurements in the Atlantic are already exceeding those observed at the same point last year. Projections for the early summer suggest that temperatures could match the elevated levels seen in 2023, raising the possibility of significantly high SSTs during the most critical period of the hurricane season.

Should these projections materialize, we could see 2024 positioned in the upper left quadrant of our diagram, signalling a season of potentially elevated hurricane activity.