La Niña’s delay could fuel an active hurricane season

Official La Niña Watch issued

Climate model forecasts for the Niño-3.4 temperature anomalies in 2024–25. Average dynamical model data (black line) from the North American Multi-Model Ensemble (NMME): darker gray envelope shows the range of 68% of all model forecasts; lighter gray shows the range of 95% of all model forecasts. NOAA Climate.gov image from University of Miami data.

JACKSONVILLE, FL – There is a great amount of research and monitoring on La Niña and El Niño since they affect the weather around the world.

Think of the two as siblings who take turns controlling the Pacific Ocean’s temperature. La Niña is the “cooler” sibling, while El Niño is the “warmer” one.

La Niña is never a good setup for us since it tends to cause more Atlantic hurricanes.

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Right now, neither sibling is fully in charge, but La Niña is expected to take over soon. This is a bit later than expected, but it should still make for a busy hurricane season.

The Latest Outlook

The Climate Prediction Center (CPC), announced Thursday, that La Niña is now anticipated to develop between August and October, aligning with the peak of hurricane season. This is a slight delay in the onset of La Niña originally expected to begin as early as July.

ENSO Neutral Phase in Effect

Since winter 2023-24, the water along the equatorial Pacific has been cooling following the peak of El Niño. We are currently in an ENSO Neutral phase, where neither La Niña nor El Niño conditions are present. However, the CPC reports a 70% chance of transitioning to La Niña within the next few months, with the pattern likely persisting through winter.

Impact on Hurricane Season

During La Niña, cooler water temperatures in the Pacific equator reduce wind shear over the Atlantic. Wind shear, which refers to changes in wind speed and direction at different altitudes, can hinder the development of hurricanes. With less wind shear, the Atlantic basin becomes more conducive to tropical storm formation.

Cooling Trends and Trade Winds

Currently, the Niño 3.4 region, a key area monitored for La Niña/El Niño conditions, has seen water temperatures cool to just 0.3 degrees Celsius above average and continues to drop. For a weak La Niña to be declared, temperatures need to cool by 0.5 degrees Celsius below average.

June 2024 sea surface temperature difference from the 1985-1993 average (details from Coral Reef Watch). The box indicates the location of the Niño-3.4 ENSO monitoring region in the tropical Pacific. The surface of the tropical Pacific is close to average temperature, but much of the global oceans remain warmer than average.

Historical Context and Variability

Historically, La Niña phases are associated with above-average hurricane seasons. However, no two La Niña events are identical. While they share common traits, such as reduced wind shear and favorable conditions for hurricane development, each phase has unique characteristics.

Forecasters emphasize the importance of monitoring conditions closely, as there have been instances where La Niña conditions were present, but the expected atmospheric changes did not occur.

Preparing for an Active Season

CSU July 2024 forecast.

Experts are calling for a hyperactive hurricane season. Just this week Colorado State University increased the forecast, now calling for 25 named storms, of which 12 would reach hurricane strength and six that would become major hurricanes.

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This is even higher than their earlier prediction in June, which already anticipated a busy hurricane season.


About the Author

After covering the weather from every corner of Florida and doing marine research in the Gulf, Mark Collins settled in Jacksonville to forecast weather for The First Coast.

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