So long La Niña…see you next Fall?

Weather Blog

Peoria, Ill. (WMBD) – On Thursday the Climate Prediction Center declared that the latest La Niña has officially come to an end and that there’s a 67% chance that we’ll be in ENSO neutral conditions through the summer.

While sea surface temperatures (SSTs) across the eastern Pacific remain well below average (-0.75°), atmospheric conditions and prevailing wind and precipitation patterns across the Pacific no longer resemble the pattern that is associated with La Niña. Forecasters also noted that water temperatures below the surface are warmer than average which means there’s no source for SSTs to remain below average. This increases confidence that La Niña has ended…at least for now.

What’s next?

Confidence is reasonably high that we’ll encounter ENSO neutral conditions, the phase between La Niña and El Niño, through the summer. The current probability of ENSO neutral conditions this summer are around 67% while the chances of an El Niño are only around 8%. From severe weather outbreaks in the U.S. to impacts on the Atlantic Hurricane season, the phase of ENSO (El Niño/Southern Oscillation) has an impact on weather across the globe.

It’s no coincidence that last year’s record setting hurricane season (30 named storms) occurred during a La Niña. There’s a strong relationship between the Atlantic hurricane season and the phase of ENSO. Stronger upper-level winds over the tropical Atlantic associated with El Niño tend to reduce the number of hurricanes and tropical storms, but during La Niña, those upper-level winds are weaker and it’s much easier from tropical cyclones to develop.

While it hasn’t been the case so far this year, more frequent severe weather outbreaks have been documented across the Midwest and the Southeast coming out of La Niña winters. While severe weather in Illinois has been nearly non-existent this year, La Niña conditions probably influenced the numerous severe weather outbreaks across the southeast in March.

Next Fall and Winter

Model forecasts suggest that there’s a greater than 50% chance we experience a second year La Niña this Fall and Winter which is not historically unusual. However, forecasters warn of the Spring Predictability Barrier where ENSO model forecasts made in the Spring are less accurate than those made at other points during the year. Because of this, forecaster confidence in slipping back into La Niña at the end of the year are lower than the models would indicate.

You can read NOAA’s latest blog and find more information on the state of ENSO here.

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