Declining confidence that a significant La Nina event will ever unfold over the Pacific

Climate experts are anxiously awaiting the declaration of a La Niña, but the global weather pattern is pointing towards it being weak.

The world has been stuck in a neutral El Niño-Southern Oscillation (ENSO) status since early summer as sea surface anomalies have waxed and waned in the range between -0.5°C and 0.5°C over the Pacific.

In recent months, cooler-than-average waters have been detected by satellites over the central and eastern tropical Pacific, but have not reached the threshold to declare a La Niña event underway.

These conditions have created variable weather patterns around the world — a situation that could continue through most of 2025, according to long-term climate models.

Earlier in 2024, most models indicated that the world would plunge into a La Niña, and a significant one at that. However, fewer and fewer model runs now predict this scenario.

A significant minority of model runs now keep the world in a neutral status for the foreseeable future, influencing extreme weather conditions in the coming winter and spring.

The latest assessment from NOAA’s Climate Prediction Center issued Thursday calls for La Niña to emerge soon, but forecasters said they expect it to be weak and short-lived.

“A weak La Niña would be less likely to result in conventional winter impacts, although predictable signals could still affect forecast guidance,” CPC forecasters wrote in the update.

Periods of weaker-than-usual trade winds over the tropics have allowed the Pacific to warm slightly, delaying the development of a La Niña event.

WHAT ARE EL NIÑO AND LA NIÑA CLIMATE PATTERNS?

What are the effects of a neutral winter in the US?

The combination of pockets of warming in the Pacific Ocean and output from computer models gives forecasters confidence that a significant La Niña is not in the cards for many months to come.

A neutral winter means neither El Niño nor La Niña conditions are in control, generally resulting in more zonal jet stream patterns. This leads to less extreme cold snaps in the northern United States and average precipitation levels in the southern part of the country.

A La Niña winter typically results in much colder and snowier conditions across the country, but again this does not appear to be in the cards for the 2024-2025 season, which begins on December 1.

The 2023-24 El Niño brought one of the warmest and least snowy winters on record across the United States, with temperatures more than 5°F above normal.

While the upcoming winter is expected to be somewhat cooler, it is not expected to set any widespread cold road records.

The combination of ENSO status and general climate warming is expected to keep temperatures above average across much of the country.

The last time the country experienced a cooler than average winter was in 2013-14, when the average temperature was almost one degree below typical values.

According to a NOAA database, the coldest winter on record was 1978-79, with the winters of 1935-36, 1898-1899, 1909-10 and 1904-05 rounding out the five coldest winters.

LITTLE KNOWN WEATHER PATTERNS WHEN EL NIÑO AND LA NIÑA ARE NO LONGER IN CONTROL

Could an El Niño come back?

Some forecast models indicate that an El Niño could return by 2025, but again, climate patterns don’t seem to be in a hurry to venture into one extreme or the other.

Since reliable observations of ENSO began in the 1950s, there have been only a few instances where a double El Niño has formed.

The period from 1991 to 1995 was characterized by a double El Niño, with a longer series of neutral conditions from 1992 to 1994.

A major unknown is the impact of climate change on the behavior of ENSO.

Rising ocean temperatures are likely to increase the frequency of El Niño events, but more research is needed to understand how warmer oceans will affect changes in the world’s ENSO status.

NOAA provides monthly updates on the status of ENSO, released on the second Thursday of each month.