Even though the first day of Fall will be 93-degrees-hot, that's not exactly an indication of what the weather will be like into the latter part of the season and into Winter.
According to NOAA's Climate Prediction Center, a "La Niña Watch" is in effect. The figure to the left shows the relative El Niño/La Niña pattern (click to enlarge). Positive numbers represent El Niño conditions with negative numbers being La Niña. The colored lines represent model solutions for the future. You can see almost all of the models have weak La Niña conditions for the next month. That means our warm, dry pattern will probably take a break. But the models also show that La Niña conditions are expected to continue and perhaps get stronger into January.
A La Niña occurs when the ocean water temperatures in the Equatorial Pacific Ocean are cooler than normal. This occurrence changes the steering currents of the upper atmosphere, changing the overall weather pattern for the next several months to a year.
With all of the models showing these conditions, let's take a look at previous La Niña winters to see what they were like. Some takeaways: cooler than normal temperatures across the western half of Canada, into the Plains and Upper Midwest. Warmer than normal temperatures occur from Texas into the Carolinas.
As far as precipitation goes, wetter than normal conditions were observed in the Pacific Northwest with dry conditions from Southern California, all the way across to South Carolina.
If you're a snow-lover, the best news is that La Niña tends to bring snowier than normal conditions for the Great Lakes States and Ohio River Valley. Here in the Quad Cities, we've had lackluster snow over the past two Winter seasons. The forecast for La Niña should be music to your ears! Eight of the top-ten snowiest winters happened in La Niña conditions.
-Meteorologist Eric Sorensen