After an extended run since last fall, the days of El Niño are over according to the Climate Prediction Center (CPC) this week. Sea surface temperatures (SSTs) have been cooling in the Eastern Pacific and are predicted to likely stay cooler through the upcoming winter.
El Niño typically occurs when the Eastern Pacific waters run above average while La Niña is the opposite. This is part of the El Niño Southern Oscillation (ENSO) that usually lasts two to seven years on average.
What the CPC is forecasting is what is called ENSO-neutral. This is sort of an in-between signal that usually sees cooling SSTs in the Eastern Pacific and a westward current of winds. Conditions are not as intense as what is seen during a La Niña though.
What we had experienced since last fall was a weak El Niño. Typically this pattern results in a more present southern jet stream with ample subtropical moisture and waves of colder air. However, what we saw was an early (but record-breaking) snow storm in December and not much else.
Overall, it was likely a disappointing winter for snow-lovers with a number of cold snaps, but not many events after December.
Looking back, our ENSO-neutral winters have been some of the snowiest winters on record including the nearly 63” 1959-1960 winter in Roanoke and many other well above average seasons. Overall ENSO-neutral seasons average 24” with nearly 7 snow events per winter. Roanoke’s average is 18.5” per winter.
While most will remember the active winters, there were also a handful of seasons when we only saw a few inches during the winter. So there definitely is some variability during ENSO-neutral winters.
While the ENSO certainly has impacts on weather patterns over stretches of time, it’s ultimately just one of many factors in the grand scheme of things. This especially should be considered for our area that tends to not see as evident of impacts from it compared to more extreme portions of the country.
When it comes to the hurricane season, ENSO-neutral can certainly make for a more active season considering the weaker westerly winds. Because of this, the National Oceanic and Atmospheric Administration has upped its expectations this year to now a 45% of an above average season.
It is important to note that this isn’t a slam-dunk forecast. There is a possibility that we see a transition back into a weak El Niño this winter or even La Niña.
Regardless, seeing that it’s only the beginning of August it’s still a bit early to make any sort of call on what will occur this winter. We will be keeping an eye on the Pacific and other factors to make our own forecast down the road. Until then, enjoy the summer heat!