Is the Pacific Ocean in an El Nino or La Nina phase?
At the moment, the Pacific is in neither. It's in what is known as a "neutral" phase.
On average, every few years, the differences in atmospheric pressure between the east and west sides of the tropical Pacific reverse. This is a natural cycle that the atmosphere goes through. This affects the strength of the easterly trade winds across the Pacific and that has a significant effect on oceanic temperatures.
When the pressure differences across the Pacific weaken, the trade winds weaken (called and El Nino) and the tropical Pacific warms. When the pressure differences are strong, the trade winds blow more strongly (called La Nina) the ocean cools.
When the Pacific is in an El Nino, or warm phase, our Central New York winters tend to be mild. When the Pacific is in a La Nina, a cold phase, our winters tend to be colder.
This year, the Pacific is in neither or a "neutral phase." Some comically call this "La Nada." So what does that mean for our coming winter?
When looking at the data from recent winters when the Pacific has been in a neutral mode, there isn't much to give us a clue about our coming winter. Snowfall totals are all over the place.
On the right is a graph of the frequency of snowfall totals over the last 50 years during El Nino-neutral seasons. There is a cluster of winters that were in the 130 inch range, but overall, the data varies widely. In other words, when in a neutral phase, the tropical Pacific Ocean is not a major factor in our winter weather.
When the Tropical Pacific is in this neutral phase, then other factors in the atmosphere become bigger players in our winter weather. Things like snow pack over the hemisphere, average Arctic temperatures, ocean temperatures in the Atlantic, all play a stronger role in the making of our winter weather.
In theory, this should mean a lot of week to week variability this winter -- just what we need to keep a meteorologist on his or her toes.
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