El Niño to La Niña transition expected, impacts likely for the PNW
PORTLAND, Ore. (KOIN) -- A strong El Niño pattern has been in place over the Pacific Ocean during the 2023-2024 winter season. This year's winter impacts of warmer weather may vary wildly as the Pacific Northwest prepares for the 2024-2025 winter season.
The National Weather Service is predicting El Niño to fade in the coming months and transition to ENSO-neutral. That's where neither El Niño nor La Niña effects are present over the Pacific Ocean. ENSO-neutral will then transition to La Niña as summer approaches.
El Niño: What it is and the impacts it has on the PNW
The Pacific Ocean is currently under an El Niño Advisory. That means the Equatorial sea surface temperatures have been recorded above average. It's these warmer sea surface temperatures that help drive different weather pattern over of the United States, especially during the winter season.
During a typical El Niño winter, the Pacific Northwest sees warmer than average temperatures. That's been consistent with Portland's warmer temperature trend this winter. Portland saw its warmest December day in 2023, with a record high of 67°F on December 4. On average, Portland experienced a warmer December and January by several degrees thanks to the El Niño influence. A wetter weather pattern is typically seen for southern California as well when El Niño is present. That's been the case with multiple atmospheric rivers taking aim at the West Coast. The frequent rain showers have caused flooding conditions over the last few months for much of the state of California.
ENSO-neutral: The temperature transition over Pacific waters
Considered "no man's land" where neither El Niño nor La Niña is present over the equatorial waters of the Pacific Ocean. Sea surface temperatures remain near average. That, too, has an impact on the weather experienced over the Pacific Northwest during the winter months.
During an ENSO-neutral winter, the Pacific Northwest sees an average amount of moisture and temperatures follow the normal winter pattern.
The ENSO-neutral stage can remain a fixture of equatorial waters or can be a sign of the transition from El Niño to La Niña. The National Weather Service is predicting ENSO-neutral to take shape as early as April-June. That means near normal temperatures and average precipitation is possible for the Pacific Northwest before the summer season take over. Climatologists are giving this scenario a 73% chance of coming to fruition.
La Niña: What that means for the 2024-2025 winter season around Portland
A La Niña Watch is in place for the equatorial waters of the Pacific Ocean by the 2024 summer months. La Niña is when sea surface temperatures dip below average. It's the cooler waters that help bring increased moisture and decrease temperatures for the Pacific Northwest during the winter months.
You'll recall, the 2022-2023 was a La Niña year. That's when Portland experienced the whopping 10.8 inches of snow in late February. A single weather event can't be to blame for the seasonal outlook, but last year's winter season brought more snow scares to the Portland area than this current winter season.
The National Weather Service is 55% confident in El Niño transitions to La Niña by June through August 2024. If that prediction comes true, then the Pacific Northwest could be in for a potentially wet and cooler than average 2024-2025 winter season.