More Snow Days Likely with El Niño
Old Dominion University students notice the unusual weather this winter, including the snowstorm two weeks ago. The El Niño Southern Oscillation (ENSO), usually referred to as El Niño, has been in effect over the 2015-2016 winter and might bring more northern storms our way.
El Niño is essentially a change in the air currents over the southern Pacific Ocean. Normally, trade winds blow from South America to Australia, pushing the warm tropical surface water with them. The action builds over distance to create westward, warm water currents.
“The trade winds weaken or shift during El Niño years,” Ben Hamlington, an oceanographer at ODU, said. This causes the warm water to sit listlessly along the South American west coast.
“It’s like if a bunch of warm water is sort of seesawing, sloshing back and forth across the whole Pacific,” Hamlington said. “This happens every two to six years.”
The result of the shift is warm, wet air sitting over the Eastern Pacific. El Niño can have far-ranging effects, from stormier winters in most of the southern US to mass fish die-off in Peruvian fisheries.
El Niño primarily affects Norfolk by bringing more storms. “The Pacific jet stream is pushed farther south,” Hamlington said. This shift brings more warm, humid air over the southern United States and the Gulf of Mexico.
“There is a significant relationship between ENSO and the South East US and mid-Atlantic, although north of Cape Hatteras, the relationship is much weaker, in part because of the shift in the jet stream,” Hamlington adds.
“We may get one or two more big storms over the winter than usual,” Hamlington said.
Most of the effects of El Niño are felt on the west coast. “Sea level rises along the western coasts during an El Nino because warm water piles up in the eastern Pacific, as a result of the shifting trade winds,” Hamlington said. “There is also more precipitation, because of more storms than usual on the West Coast.”
“While it is good news that drought improvement is predicted for California, one season of above-average rain and snow is unlikely to remove four years of drought,” Mike Halpert, Deputy Director of NOAA’s Climate Prediction Center, said.
The weakened winds over South America have another effect: crashing fisheries in Peru. Strong winds pushing warm water west also pull up colder, more nutrient- and oxygen-rich water from the depths. When these winds slack in El Niño years, low-oxygen, low-nutrient zones pop up along the west coast of South America, sometimes leading to massive fish die-off.
Although the currents causing El Niño and La Niña are thousands of miles away from Norfolk, ODU feels significant effects. The strength of El Niño has been increasing for the past few cycles, although it is currently unclear how El Niño might be affected by climate change.
ODU may see more snow yet.