Forecasters at the National Oceanic and Atmospheric Association (NOAA) believe the new El Niño water temperature phenomenon has a greater than 90 percent chance of lasting through the winter and into 2024.
El Niño conditions mean that ocean temperatures in the eastern Pacific are higher than normal, which can cause a less severe winter for much of the northern U.S. and more rain for the south, as the jet stream is forced north.
Eastern Pacific waters more than 0.5 degrees Celsius above normal are considered El Niño conditions. Temperatures were 0.8 degrees above average as of June and are anticipated to rise to as much as 1.5 degrees above average in the last few months of the year, when El Niños usually peak.
However, NOAA forecasters said the standard effects of an El Niño — milder winters and fewer hurricanes — may be reduced by a globally warmer ocean.
“One potential outcome is a weaker atmospheric response than we might otherwise expect. The strength of the atmospheric response is related to the pattern of sea surface temperature throughout the tropics,” Emily Becker, a University of Miami climatologist, wrote for NOAA.
“However, when the western Pacific and the rest of the tropics are also warm, the response may be more muddled,” she added.
Earlier this month, hurricane forecasters at Colorado State University (CSU) said that this hurricane season is expected to be above average despite the El Niño, because Atlantic Ocean temperatures are also above average.
“The extreme anomalous warmth in the Atlantic may counteract some of the typical El Niño-driven wind shear,” CSU’s Phil Klotzbach said.
NOAA forecasters said there is an 80 percent chance that the peak of the El Niño this winter will be at least in the normal temperature range, a 50 percent chance that it is at least severe and a 20 percent chance that it will be very severe — or more than 2 degrees Celsius above average.
An El Niño is caused by weaker than normal trade winds in the Pacific, which causes warmer water to stick around in the eastern Pacific instead of being blown west. In years where trade winds are stronger than normal, called La Niñas, the eastern Pacific is colder than normal, usually causing more severe winters in the northern U.S., droughts in the south and more hurricanes than normal.