Arkansas Storm Team Blog: A La Niña watch has been issued

A lot of the weather that impacts the Continental United States, Alaska, and Canada is related to what conditions are ongoing in the equatorial Pacific. Specifically, what phase of El Niño Southern Oscillation (or ENSO) is occurring or going to occur, which is determined by sea surface temperature anomalies in the equatorial Pacific Ocean. When sea surface temperature anomalies are warmer than normal by a certain extent for some time, El Niño is likely. When sea surface temperature anomalies are cooler than normal by a certain extent for some time, La Niña is likely. When an El Niño phase occurs in the winter, a lot of low-pressure systems are sent through the southern U.S., and as a result, Arkansas experiences a generally cooler and wetter winter. When a La Niña phase occurs in the winter, a lot of low-pressure systems move through the northern U.S., leaving Arkansas near-normal or warmer and drier than normal.

As of September, a La Niña watch has been issued for October to December. A La Niña watch means conditions are favorable for the development of a La Niña phase within the next 3 months. There’s a 71% likelihood that a La Niña phase develops from October to December, and a 54% likelihood that La Niña continues through February of 2026. This follows an ENSO-neutral phase, which was noted near or just slightly below normal sea surface temperatures in August.

Since August, below-normal sea surface temperature anomalies have been recorded, thunderstorm activity has decreased near the equatorial Pacific, low-level easterly winds have increased across the tropical Pacific, and upper-level westerly winds have increased in the tropical Pacific. These occurrences prompted the La Niña watch. This means from October to possibly February, Arkansas has a likelihood of a near-normal to a slightly warmer and drier-than-normal winter in store.