La Niña is expected to shift to a neutral pattern by February and should continue this trend through the first half of the year, according to a recent diagnostic discussion from the National Oceanic and Atmospheric Administration. However, weather patterns across the U.S. are still likely to be affected by the weakened La Niña.
"Even as the tropical Pacific Ocean returns to ENSO-neutral conditions, the atmospheric impacts from La Niña could persist during the upcoming months," the diagnostic discussion said.
La Niña is the counterpart to El Niño and is characterized by lower-than-normal sea surface temperatures across the equatorial eastern and central Pacific Ocean. A La Niña event often brings more supportive fundamentals for U.S. natural gas and electricity markets, including a higher probability of colder winters in northern regions, hotter summers and increased tropical activity in the Atlantic basin.
While recent outlooks have pointed to the possible re-emergence of El Niño during the second half of the year, forecasters from NOAA are skeptical. El Niño is the periodic warming of central and eastern tropical Pacific waters and occurs every two to five years, on average, typically lasting about a year in length.
"We're not placing a lot of confidence in these forecasts and are favoring ENSO-neutral (50% chance during August-October 2017), but the remaining odds are not evenly split: we are tilting the odds toward El Niño (35% chance) over La Niña (15% chance). Forecasts of ENSO made in the winter and early spring have historically not been very skillful (the 'spring predictability barrier'). Also, there are no strong signs right now giving us a good picture of what the summer and fall will look like," NOAA said in an accompanying blog post dated Jan. 11.
NOAA's latest three-month temperature forecast for February through April, updated Jan. 19, is calling for above-normal temperatures across much of the East, the southern tier of the U.S. and areas of the Southwest.
Equal chances of below-normal, normal and above-average conditions are eyed for the much of north-central region, the Midwest and most of the West Coast through the period. Below-normal temperatures are anticipated for a swath of the Pacific Northwest into a region of the upper Midwest over the next few months.
NOAA's forecast for the next three months is also calling for above-average precipitation levels in the Pacific Northwest and Upper Midwest. There are equal chances for below-normal, normal and above-average precipitation for the Northeast, Mid-Atlantic, the remainder of the central U.S. and much of the West Coast through the period. The Southeast and a small area of the Southwest should see below-average precipitation levels from February to April.