- NOAA meteorologists believe that La Niña could form as early as September.
- La Niña is expected to persist throughout the winter months.
- Although a weaker La Niña phenomenon is forecast, impacts could still occur across the country.
Meteorologists at NOAA’s Climate Prediction Center believe La Niña could form as early as the coming weeks. In an update Thursday, meteorologists said there is a 71% chance that La Niña conditions will occur sometime between September and November and persist through the winter months. Therefore, a La Niña warning remains in effect.
What is a La Niña clock? A La Niña warning is issued when La Niña conditions are expected to occur within the next six months. La Niña occurs when ocean surface temperatures are cooler in the central and east-central equatorial Pacific, which can affect weather patterns around the world.
(MORE: What is La Niña? A deeper look)
Neutral conditions continue to apply: Temperatures in the eastern and central Pacific Ocean near the equator have been near average this month, meaning that neither El Niño nor its counterpart La Niña are ongoing. As a reminder, El Niño conditions were declared over in June.
Sea surface temperatures in the equatorial Pacific are currently a mix of cooler and warmer waters, as shown in the map below, which is an indication of the neutral conditions that still exist at present. Water temperatures in this region of the Pacific need to approach a cooler threshold for La Niña to develop.
This image shows below-average temperatures along the equator in the Pacific Ocean.
(For even more detailed weather tracking for your area, see our 15-minute detailed forecast Premium Pro Experience.)
The forecast: The cooling process of sea surface temperatures associated with La Niña has so far been slower than originally expected, according to NOAA. However, conditions in the atmosphere and ocean remain favorable for the development of La Niña in the coming weeks.
However, meteorologists also expect that La Niña, once it develops, will be weaker. This means that the typical effects of La Niña in winter may not be quite as dramatic.
Why this is important: The cooling effect of La Niña on the equatorial Pacific waters can affect weather patterns thousands of miles away, including near the U.S. While La Niña is far from the only cause of the weather pattern, here are some effects you might see during this transition to La Niña:
- Continuation of an active Atlantic hurricane season. We have already seen six named storms this season, including three hurricane landfalls in the US with Beryl, Debby and Francine. Colorado State University’s updated forecast, released in early August, still calls for an active season, even though the US was in a tropical doldrums for the six weeks before Hurricane Francine. One reason for the continued active forecast is the expectation of further development toward La Niña conditions, which typically reduce wind shear in the atmosphere. Reduced wind shear is a factor that can favor the formation and intensification of tropical storms and hurricanes.
During La Niña winters, wetter conditions prevail in the Ohio Valley and the Pacific Northwest, while drier than normal conditions prevail in the southern United States.
- For the United States, La Niña typically means a warmer, drier winter in the South and a colder winter in the Northern Plains. Winter is also wetter than normal in the Pacific Northwest and the Ohio Valley, and is typically drier in the South.
La Niña winters often mean warmer than average temperatures in the southern United States and cooler than average temperatures in the northern United States.
