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La Niña appears to be headed our way. What does that mean for WNY?

This is a Facebook post I made on July 9, last summer: “The newest El Niño Advisory released through NOAA July 9 increases probabilities for a stronger El Niño with greater longevity to last through this coming winter. IF -- a big IF -- this occurs, it would lessen probabilities for another excessively cold winter in our part of the region and increase probabilities of a milder than average winter. In fact, a strong El Niño is one of the relatively few leading signals from nature of such a trend.”

When models are in good agreement a strong El Niño will be developing in the fall and last through most of the following winter, that can be one of the more reliable trends forecasters can use to make a somewhat more confident winter outlook, at least as far as temperatures go.

This last El Niño sent its footprint to many parts of the world, including our region, producing a dramatically milder winter than the extraordinarily cold previous winter of 2014-15 in our region.

The oscillation of warmest tropical waters back and forth across the near equatorial Pacific waters is a phenomenon called the El Niño Southern Oscillation (ENSO). ENSO has three primary phases: El Niño, neutral and La Niña. El Niño brings warmer than average water temperatures toward the eastern Pacific.

We currently have neutral ENSO conditions, in which the extreme warmth in the east central and eastern Pacific is gone and near-surface sea temperatures are closer to average. But the majority of the many models used to predict ENSO are in pretty good agreement that we are headed into La Niña, in which cooler than average temperatures occur in the eastern Pacific and the warmer temperatures build in the western Pacific. Readings are already a little cooler than average and are expected to reach La Niña status either later this summer or early fall.

That might tempt some to think this might produce the opposite effect of an El Niño in our region, with La Niña certainly bringing a colder winter. Not so fast. For our region, the effects of even a strong La Niña are not conveniently opposite to those of a strong El Niño.

A stronger La Niña tends to be associated with cooler and wetter than average conditions over the north central states but not the northeast and eastern Great Lakes. In fact, Buffalo National Weather Service meteorologist Robert Hamilton has done a statistical analysis that shows strong La Niñas actually tend to produce milder winters in our region. But the majority of models are tending toward a weak La Niña this time around. And as far as ENSO and our region go this winter, that becomes a crapshoot factor. Because there are so many other oscillating patterns in the atmosphere and oceans besides ENSO, a weak ENSO signal tends to open the door for greater impact from other oscillations, such as the North Atlantic Oscillation.

This year, it appears we can’t rely on much of a signal from ENSO. Had this past El Niño been weak (it was one of the two strongest on record), there is a good chance our winter would not have been nearly as mild.

Another signal some amateur sleuths like to think about is a warmer than average Lake Erie and lake effect.

As of this writing, the Buffalo Lake Erie temperature is 73, which is three degrees above average for the date. That is not a large departure from normal.

Even if the lake is much warmer than average (closer to 78-80 degrees) in mid-July, that is not necessarily much of a harbinger of lake-effect potential. I’ve observed quite a few autumns when we’ve started with a warm lake anomaly only to see it vanish during a cooler than average October or early November. If Lake Erie is still significantly warmer than average by mid- to late autumn, more lake effect could occur if wind direction and temperatures are conducive for it.

I guess it’s safe to conclude we have no real idea of how this next winter will go other than to say statistical probabilities do not favor as mild a winter as that of 2015-16. That doesn’t mean we’re headed toward a dramatically colder winter. It means we don’t know. With that inconclusive conclusion, thanks for reading this far!

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