La Niña wavers, calling our winter weather into question

Weather Blog

Current sea surface temperature anomalies, with yellow representing warmer than normal water and blue showing cooler than normal water

The natural push and pull between El Niño and La Niña patterns — Pacific Ocean temperatures near the Equator fluctuating warmer or cooler than normal — has a large impact on global weather patterns, including in Central Texas. And the moderate to strong La Niña expected to cause a milder than normal winter in Austin may be disappearing before our eyes.

Ocean temperature anomaly trends over the last year. Notice how ocean temperatures in the Nino 3.4 region were coolest in November and have now been warming

Ocean temperatures, especially in the “Nino 3.4” region of the Equatorial Pacific used to diagnose an El Niño or La Niña event, were at their coolest levels in November, 2020. An anomaly of -1.8°C qualifies this, at least briefly, as a strong La Niña.

Since that time, however, those ocean temperatures have been warming and are now only -1.1°C off their normal value — a “moderate” event.

Ocean temperature change over the last month. Notice the warming in the Equatorial Pacific, meaning the La Niña pattern is weakening

NOAA seasonal forecasters give this La Niña a 95% chance of continuing through February, but a 50% chance of transitioning to a neutral pattern by springtime.

La Niña patterns in the Pacific Ocean typically lead to drier and warmer than normal winter weather in the Austin area. And Camp Mabry’s monthly average temperatures show that well as the pattern hit its peak in November. But notice below how Austin’s temperatures have become less anomalously warm since that time, and are even cooler than average so far in January.

  • November, 2020: +5.3°F
  • December, 2020: +2.4°F
  • January, 2021 (to date): -1.8°F

In addition to cooling temperatures in our local area since November, we have noticed that the ocean-atmosphere connection of the La Niña event has been largely lost as well.

During a La Niña, our weather is benign and warm because the jet stream moves farther north, keeping storms away from our area. But for several weeks now, and for the foreseeable future, the jet stream has been taking dips into Texas, bringing with it storms, cold fronts, and even the recent significant winter storm.

Stay with the KXAN First Warning Weather team as this large-scale pattern shift could mean more volatile winter weather.

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