A La Niña watch remains in effect this month as forecasters watch a key region in the Pacific Ocean for signs of change that could influence weather patterns here at home.
The U.S. Climate Prediction Center (CPC) issued its monthly outlook on Thursday, in which it called for a better-than-even chance of La Niña emerging through this winter.
However, the atmosphere is already acting like we’re in La Niña.
Get all the latest news on El Niño and La Niña at The Weather Network’s hub page!
The CPC’s monthly outlook gives a 59 percent chance of La Niña developing by January 2025, with a return to neutral conditions expected by next spring.
La Niña occurs when ocean waters around the equator in the eastern Pacific Ocean run at least 0.5°C colder than normal for about seven consecutive months. El Niño is the direct, warm-water opposite of La Niña.
Water temperatures in the eastern Pacific Ocean can have a far-reaching effect on weather patterns around the world. Here in Canada, a winter influenced by La Niña can foster cooler conditions for the western half of the country while a volatile pattern sets up across the east.
The 0.5-degree rule is the traditional method that experts with the CPC use to officially declare a La Niña or an El Niño. But the atmosphere doesn’t wait for official declarations.
Conditions like trade winds and rainfall patterns throughout the Pacific basin are already acting like we’re solidly in a La Niña despite the fact that sea surface temperatures haven’t yet crossed those predefined thresholds. How is that possible?
MUST SEE: La Niña’s sputtering role in an uncharted season ahead
Together, El Niño and La Niña are linked to the El Niño-Southern Oscillation (ENSO), which is the cycle of prevailing winds that pushes and pulls on surface waters across the Pacific Ocean.
ENSO represents a delicate relationship between air and water. The atmosphere influences the ocean, and in turn the ocean influences the atmosphere.
Even though there are at least two parts to the equation, forecasters largely rely on sea surface temperatures to determine whether or not we’ve ‘officially’ entered an El Niño or La Niña pattern.
This traditional method doesn’t take into account atmospheric changes that can occur before official sea surface temperature anomalies have a chance to measure up.
The complex interaction between ocean and atmosphere is a reminder that weather exists on a spectrum. Few storms or patterns ever fit neatly into our predefined boxes. So even though we’re not officially in a La Niña just yet, the atmosphere is certainly acting like it.
