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Winter Outlook Part 3 - La Nina

La Nina continues to strengthen as we head into winter. You can spot the cold waters off the South American west coast along the Equator. This La Nina is not nearly as strong as last year at this time.

(SEA SURFACE TEMPERATURE ANOMALIES IN OCTOBER)

The cold water extends well below the surface (200+ meters), so we will probably see some strengthening over the next couple months. Most computer forecasts also show this trend.

(TEMPERATURE ANOMALY BELOW THE SURFACE ALONG THE EQUATOR)

So what typically happens in a La Nina winter? As I stated in Part 1 of my outlook, there really isn't "normal" weather. We can calculate an average of all La Nina winters, so that you can get a general idea, but  I want to emphasize that each winter is unique.

You can see on the map below that La Nina will bring above average temps in parts of the Midwest and the Deep South. Below average temps prevail in the Northern Plains and Pacific Northwest. Unfortunately this map uses the 1971-2000 averages instead of the 1981-2010 averages.

(TEMPERATURE ANOMALY DURING  LA NINA)

Look at last winter's temperatures. They barely match the map above. It was cold across the entire eastern half of the United States. However, cold weather in the Northern Plains verified.

(TEMPERATURE ANOMALY FROM LAST WINTER)

Now let's look at the impact of La Nina on precipitation. La Nina winters on average will bring excessive rain to the Pacific Northwest and the Ohio River Valley. The Gulf Coast will remain extremely dry while the Midwest, Mid-Atlantic and Southwest U.S. will stay marginally dry.

(PRECIPITATION ANOMALY DURING  LA NINA)

The precipitation from last winter actually fit the averages fairly well. It was very dry in the Deep South with below average precip also in parts of the Midwest and Mid-Atlantic. However, Southern California and parts of Nevada received above average precip, which doesn't match the typical La Nina winter. In addition, Northern California stayed mysteriously dry.

(PRECIPITATION ANOMALY FROM LAST WINTER)

Now let's look at the Climate Prediction Center's forecast for this winter. You can see that their forecast is heavily influenced by La Nina conditions. They are going for heavy precipitation in the Pacific Northwest, Northern Plains and Ohio River Valley.

(CPC PRECIPITATION FORECAST FOR THIS WINTER)

CPC is forecasting a warmer than average winter in Texas and southern parts of the Midwest. They are expecting extremely cold conditions in the Northern Plains with slightly cooler than average temps along the entire West Coast.

(CPC TEMPERATURE FORECAST FOR THIS WINTER)

Although I agree with some parts of this forecast, I feel that they are taking the easy way out. It seems that they are just taking the average La Nina year and applying it to their forecast.

This year could easily end up being a "La Neutral" or a "La Nada" for a lot of people this winter. In other words, there are other factors that will impact this winter's weather and I will address them in my next update.

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