La Niña has developed and is expected to influence temperature and precipitation patterns in the United States over the next several months.
During La Niña winter typically:
-The southern U.S. experiences above-average temperatures and below-average precipitation.
-The northern U.S. experiences below-average temperatures (particularly the Northern Plains and Northwest) and above-average precipitation.
These themes develop due to the upper-level pattern, which includes an upper-level ridge of high pressure near the Aleutians that pushes the jet stream northward over Alaska and then southward to near the U.S./Canada border. This keeps colder air across the northern tier. Additionally, the storm track is further north, leaving the South dry and warm.
However, La Niña, El Niño or the lack of either, is just one piece of the atmospheric puzzle. Other influences in the atmosphere can override what's typically expected in a La Nina winter, but those factors can't be determined until winter is in full swing.
Above are the general impacts in the U.S. when La Niña is present in winter. The conditions can vary based on the strength of the La Niña event and other atmospheric influences.
What Is La Niña and Why Was It Declared
La Niña is the periodic cooling of the equatorial eastern and central Pacific Ocean. When sea-surface temperatures are cooler than average by at least 0.9 degrees Fahrenheit (0.5 degrees Celsius), along with consistent atmospheric indications for at least three consecutive months, La Niña is present.
The interaction of this cooler-than-average water with the atmosphere can affect weather conditions thousands of miles away in the U.S. and around the world.
Below average sea-surface temperatures strengthened significantly over the past month and extend across the central and eastern equatorial Pacific Ocean. Atmospheric conditions also demonstrate that La Niña has developed, according to the latest outlook issued by NOAA on Thursday.
As a result, NOAA issued a La Niña advisory, meaning La Niña is present.
The blue contours in the area boxed above show the development of cooler than average sea-surface temperatures in the equatorial Pacific Ocean as of early October.
NOAA says there is an 87% chance La Niña will persist through the winter. Most computer models agree and suggest that La Niña will last through at least February.
A moderate strength La Niña is also expected at its peak, likely in the November through January period, NOAA noted.
Blue bars indicate probabilty of La Niña, which models indicate is likely to last through this winter.
(CPC/IRI)This will be the second winter in a row with La Niña, or a "double-dip." Last year, La Niña developed in August and dissipated in April 2021.
The potential development of La Niña was a factor in the above-normal hurricane season forecast, according to Mike Halpert, deputy director of NOAA's Climate Prediction Center.
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