Recently, colder-than-normal waters have been observed off the west coast of South America, along the equator. This is the region we look at for the ENSO signal -- which stands for El Niño Southern Oscillation. That is the back-and-forth warming and cooling of waters that gives us El Niño or La Niña.
The temperature of that patch of water tends to affect the jet stream patterns across North America, which then directs storm systems.
Those cooling waters look as if they could persist into the end of 2020, which would lead to a La Niña fall and winter!
Thus, NOAA has issued a “La Niña Watch” for the fall and winter, as the chances of a La Niña fall and winter is now 85 percent.
It is very important to remember that the predictions for ENSO are not foolproof and even if El Niño or La Niña occurs, there’s no guarantee it would have the expected effects on our weather in the Pacific Northwest.
Still, if La Niña does occur, it could lead to an increase in storminess here in the Northwest, with a greater chance of above-normal mountain snow and a somewhat increased likelihood of lowland snowfall events.
Think of La Niña as “weighting the scales” a little toward cooler, wetter and possibly stormier weather patterns late in 2020 and early 2021.
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