La Niña Watch issued as conditions favor development — what does it mean for Central Texas

Weather Blog
La Nina model 2021

(KXAN) — The Climate Prediction Center (CPC) has issued a La Niña watch as development chances increase for the Northern Hemisphere heading into fall and winter.

This comes as the Northern Hemisphere is currently in what is called “ENSO-Neutral”. ENSO stands for El Niña Southern-Oscillation and is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean that drives the development of La Niña and El Niño.

The CPC forecasts that there’s a 51% chance of ENSO-Neutral conditions continuing through the summer and beginning of fall with La Niña potentially emerging during the September-November season and lasting through the 2021-22 winter (66% chance during November-January).

According to the National Weather Service, La Niña forms when there’s a cooling of the ocean surface, or below-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to increase while rainfall decreases over the central and eastern tropical Pacific Ocean.  The normal easterly winds along the equator become even stronger.  In general, the cooler the ocean temperature anomalies, the stronger the La Niña (and vice-versa).

Current forecast models are beginning to indicate that eastern tropical Pacific Ocean SSTs to dip anywhere from around 0.5°C to 1.0°C. If this were to pan out, moderate La Niña conditions would be possible.

Forecast courtesy of The National Weather Service

What this means for us in Central Texas is a drier and warmer fall/winter. After a wetter and cooler than normal first half of 2021 for most of Central Texas, a dry stretch of weather could benefit us, but only in the short term, as drought conditions usually increase during La Niña winters. La Niña can also lead to a more severe hurricane season.

La Niña causes the jet stream to move northward and to weaken over the eastern Pacific. During La Niña winters, the South sees warmer and drier conditions than usual. The North and Canada tend to be wetter and colder.

A lot can change between now and this fall, which is why just a “watch” is issued at this time. Stay up to date with the latest as more forecasts come out here.

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