It appears La Nina had so much fun messing with our winter last year that it's decided to come back for an encore.
NOAA’s Climate Prediction Center officially upgraded our La Nina Watch to a La Nina Advisory, which in essence means La Nina conditions are forecast to return for the fall and winter.
A quick recap: La Nina is part of a 3-7 year cycle where ocean temperatures in the Equatorial Pacific Ocean region drift from warm to cold, then back again. The warm phases are called El Nino, the cold phases are La Nina, and "neutral" is what we get when they're in the middle, or average. The shift in water temperatures has a cascading effect on global weather patterns that begin with a change in the trade winds near the equator.
La Nina winters typically spell cool, wet (and snowy) winters around here while El Nino winters are typically warm and dry.
Forecasts through the summer had shown moderating ocean temperatures and a return to "neutral" conditions (neither El Nino nor La Nina. By the way, those winters tend to run the gamut of conditions) and the expectation was that we would stay neutral through this winter.
But a funny thing happened on the way through the summer -- the atmosphere never really noticed La Nina died and La Nina-esque conditions have persisted. And now, as we went into August, the ocean waters began cooling once again, raising eyebrows that perhaps La Nina wasn't finished with us just yet.
And now, as we draw into September, almost all areas of the ocean that are monitored for La Nina have cooled back into the threshold to where it's official La Nina conditions.
Forecast models are still somewhat split on what will happen from here -- there are still a few touting neutral. But one new model in particular that has been performing well has been strongly in La Nina's camp for a while now.
And NOAA says combining that model, with the current La Nina conditions both in the water and in the atmosphere, and the propensity for La Ninas sometimes to go back-to-back, leads them to believe La Nina is here and will strengthen as we head through the fall into winter -- although how strong is uncertain. (This past winter was quite a strong event -- and it doesn't seem like we'll reach that level.)
As I alluded to, these "Double Dip" La Ninas are not unusual -- NOAA says there is a standing 50 percent chance of a secondary La Nina to follow a strong event as we had last winter. Usually the second dip is weaker than the first. (NOAA did say this event will count separate from last winter's La Nina, which officially ended in May.)
That said, last fall and winter didn't really follow a typical La Nina script -- La Nina didn't really rev up until February and March. Perhaps this winter could be different since we have a head start now.
So, it's good news for skiers, snowboarders, and rain lovers as the fall and winter looks like a banner one. It's not good news for the south because La Nina has the opposite effect of maintaining very dry weather there. La Nina's also typically enhance the hurricane season, as we've already seen this year.
But suffice to say, this current warm and dry stretch's days are numbered.