A rapidly strengthening El Niño could become the strongest on record, potentially suppressing Atlantic hurricanes this fall while increasing North Carolina’s chances of a wetter winter after months of drought strained water supplies across the state.
NOAA’s Climate Prediction Center said Thursday there is a greater than 90% chance of a “very strong” El Niño developing during the fall and winter. Forecasters say there is nearly a 70% chance it reaches an intensity not seen in NOAA records dating to 1950.
“We never know exactly what’s going to occur, but in North Carolina during an El Niño, we tend to see wetter weather,” said Lindsey Long, a meteorologist with NOAA’s Climate Prediction Center. “So we can expect more rainfall over North Carolina this winter.”
What is El Niño?
El Niño is a naturally occurring climate pattern that begins in the tropical Pacific Ocean but can alter weather thousands of miles away.
Normally, trade winds near the equator push warm surface water westward across the Pacific. During El Niño, those winds weaken, allowing warm water to shift eastward and changing atmospheric circulation.
Long said weakening trade winds and pulses of warm water moving across the Pacific are helping this year’s El Niño intensify.
NOAA measures El Niño using the Relative Oceanic Niño Index, or RONI, which compares temperatures in a key region of the equatorial Pacific with temperatures across the broader tropical oceans. The measure is designed to better account for the background warming of the world’s oceans.
The strongest El Niño in NOAA’s record reached a RONI value of 2.5 degrees Celsius above normal during the 1982-83 event. Long said forecasts indicate this event could reach 2.5 to 2.6 degrees Celsius this winter, potentially setting a new record.
July already had the second-highest sea surface temperatures NOAA has recorded in the Niño 3.4 region, Long said.
What could El Niño mean for hurricane season?
For the East Coast, a strong El Niño can come with an unusual benefit during hurricane season.
El Niño typically increases vertical wind shear over the Atlantic. Those changing winds at different levels of the atmosphere can disrupt developing tropical systems, making it harder for hurricanes to organize and strengthen.
“For hurricanes, that’s kind of a killer,” Long said. “The winds in upper levels just destroy the structure of the hurricane, and so they can’t really get going.”
Long said that effect is already contributing to relatively quiet Atlantic activity this August, despite very warm Atlantic waters that would otherwise be favorable for storms.
El Niño does not eliminate the threat of hurricanes or guarantee North Carolina will avoid a landfall. It shifts the odds toward less overall Atlantic activity.
Could El Niño help North Carolina’s drought?
The effects could continue long after hurricane season ends.
El Niño tends to favor wetter-than-normal conditions across the southern United States during winter, including North Carolina.
That could be particularly significant this year.
North Carolina experienced its second-driest January through June on record, with rainfall nearly 9 inches below normal. Earlier this summer, low reservoirs and other water supply concerns prompted mandatory conservation measures in several communities.
Long said a wetter winter could help ease some of that pressure, although there is no guarantee.
“I know that you guys have had a very severe drought that’s been long-lasting, so hopefully this will help decrease that burden on the water supply,” Long said. “But again, no guarantee, but it does greatly increase the odds that we’ll see some wetter weather.”
More precipitation could also mean more opportunities for snow or ice if storms coincide with sufficiently cold temperatures.
“I would say the odds are higher for winter weather, just because of increased chances for precipitation,” Long said.
Record strength doesn’t guarantee record impacts
Even if this El Niño becomes the strongest measured by NOAA, that does not mean North Carolina will experience record impacts.
Each El Niño develops differently, and the phenomenon changes the probability of certain weather patterns rather than determining exactly what will happen in a particular place.
Long said NOAA’s forecast should be viewed as an opportunity to prepare for a potentially wetter season while continuing to follow shorter-term forecasts as winter approaches.
The event is also developing amid unusually warm oceans globally, but scientists are still studying exactly how human-caused climate change may alter El Niño and La Niña.
NOAA expects El Niño to continue strengthening through the fall and peak during the coming winter.
