What is El Nino and why does it matter during hurricane season?

Two weeks before the start of the Atlantic hurricane season, National Oceanic and Atmospheric Administration researchers have announced that the chance of the ocean-warming event known as El Niño developing this year is at more than 90%.

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That could be good news for those who live along the Atlantic and residents of the Gulf Coast states.

The El Niño phenomenon favors stronger hurricane activity in the central and eastern Pacific basins and suppresses it in the Atlantic basin.

How does El Nino work? Here’s a look at the naturally occurring phenomenon.

What is El Nino?

An El Nino, Spanish for “little boy,” is a change in the climate pattern that leads to unusual warming of surface waters and the atmosphere. The change of pattern happens in the Pacific Ocean near the equator, and the change is temporary.

What causes El Nino?

Strong trade winds usually blow from east to west across the Pacific near the equator, causing warm water to be pulled westward and pile up in the western part of the Pacific.

The winds also pull the deeper, colder water in the eastern Pacific to the surface as they move westward.

During an El Nino, the usually strong trade winds are weaker. The weaker winds don’t pull warm waters westward and the warm waters they do pull tend to fall back toward the east, making the waters near South America warmer.

What does it matter if the water is warmer in the eastern part of the Pacific?

Warmer water in the eastern Pacific tends to make trade winds weaker. Weaker westerly winds (trade winds) lead to increased rainfall in the eastern Pacific, while at the same time causing dryer conditions in the western Pacific.

How does that affect hurricane season in the Atlantic?

If the El Nino effect is strong in a particular year, it can suppress the formation of hurricanes in the Atlantic through wind shear.

Wind patterns produced by El Nino align to cut off (or shear) a tropical storm’s source of power – warm water and warm, moist air.

How will regular weather patterns be different under El Nino conditions?

El Niño generally causes wetter and cooler weather during the winter and spring for the South.

What is La Nina?

La Nina is the opposite of El Nino. National Geographic explains how La Nina works.

How often does El Nino happen?

El Nino conditions happen about every three to seven years.