La Nina is back: What does that mean for Central Pa.?


(WTAJ) — A climate pattern that is known as La Nina has redeveloped and is expected to be around for the second winter season in a row.

According to a report from the Climate Prediction Center, there is an 87% chance that the La Nina will stay through the entire meteorological winter which extends from December through February.

What is La Nina? It is when stronger trade winds along the equatorial Pacific Ocean bring cooler water up from the depths of the ocean along the coast of South America and spread it westward.

As seen in the chart below, we were in a La Nina state last year, warmed some from the spring into the summer but have now dipped down to levels lower than last year’s event.

Equitorial Pacific heat anomaly courtesy of NOAA

The change in the temperature across a significant portion of the world’s largest ocean affects the flow of air across the entire globe. This shifts jet stream flows and precipitation patterns. Some places tend to be warmer, some tend to be colder.

Here in North America, there is a strong correlation of La Nina bringing drier and warmer weather to much of the southern United States. Often the jet stream will bring colder and wetter weather to the Pacific Northwest. There is also usually will be an uptick in precipitation across the Midwest and Ohio Valley regions in the battle zone between the cold and the warmth.


As seen in the image above, there are areas where there is no significant bias in winter weather. Central Pennsylvania is one such area. What does that mean for our winter? It means other ocean temperatures and growth of snow cover dictate more on our winter trends.

WTAJ’s Weather Team will have all of those details in our Wintercast that will air in a half-hour special on Wednesday, Nov. 17 at 7:30 p.m.

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