El Niño and La Niña – Discovering Atlantic Weather Patterns

NOAA’s eagerly awaited hurricane forecast was released for 2024, anticipating an “above normal” season. NOAA cited the likely shift of oceanic and weather conditions from El Niño to La Niña as a probable influence.

What are El Niño and La Niña?

El Niño and La Niñ are part of the El Niño -Southern Oscillation (ENSO) cycle.

ENSO is a collective term for a set of recognised atmospheric and ocean changes (weather patterns) that take place in the Pacific and Atlantic oceans and regions. As the name suggests, the climate pattern tends to shift from one to the other every 3 -7 years. These changes have a massive impact on the resulting weather, influencing everything from hurricanes to droughts.

El Niño is considered the warm phase of the cycle and, La Niña the cool. When EL Niño is present, the surface waters in the tropical (central and eastern) Pacific are unusually warm and the atmospheric air pressure drops.

When LA Niña is present, the majority of the Pacific Ocean is cooler than usual and air pressure rises leading to stronger than usual pacific winds.

Since December 2023 ENSO was in the warmer El Niño phase, but NOAA is predicting a shift into La Niña, right in time for the 2024 Atlantic hurricane season.

How does El Niño & La Niña Impact Hurricane formation?

The impact of the ENSO cycle will depend on the region.

El Niño increases the likelihood of hurricanes in the central and eastern pacific and reduces it in the Atlantic. Conversely, La Niña decreases the likelihood of hurricanes in the central and eastern pacific and increases it in the Atlantic.

The main hurricane factor that ENSO affects is vertical wind shear, strong vertical wind shear can hinder and even prevent a hurricane from forming. In the regions where El Niño or La Niña are hindering hurricane formation – wind shear will be high.

This hurricane season, when the shift to La Niña takes place, wind shear strength is expected to drop within the Atlantic region, reducing an important obstacle to hurricane formation.

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