As serious drought conditions linger in parts of Oklahoma, the chances of an El Nino weather pattern developing this winter are slipping.
And if an El Nino pattern does develop, exactly what that would mean for weather in Oklahoma is even less clear.
Last week, forecasters at the National Oceanic and Atmospheric Administration’s Climate Prediction Center downgraded the El Nino forecast from an 80 percent likelihood to about 65 percent. Although that still leaves a roughly two-in-three chance that an El Nino will develop, forecasters predict it will be a weak to moderate pattern.
El Nino patterns occur when unusually warm water off South America’s Pacific coast affects atmospheric conditions, causing changes in the weather worldwide. El Nino — Spanish for “the boy” — is a reference to the Christ child, because of the pattern’s tendency to appear around Christmas.
Michelle L’Heureux, a climate scientist with the Climate Prediction Center, said forecasters look for persistent, continuous patterns in the tropical Pacific Ocean when making El Nino predictions. So far, forecasters haven’t seen much consistent data that would point to an El Nino pattern, she said.
Despite that lack of data, the odds of an El Nino winter are still fairly high, L’Heureux said. A 65 percent chance represents a downgrade from previous forecasts, but it still means an El Nino pattern is likely to develop. If a pattern does develop, though, it’s likely to be weak or moderate, she said, meaning the impact would be limited.
“It’s still a fairly high likelihood,” L’Heureux said.
But forecasters elsewhere are less optimistic. In Australia, where El Nino weather patterns typically bring severe drought, the national Bureau of Meteorology placed El Nino chances at about 50 percent last month.
If an El Nino weather pattern does emerge this winter, the impact it would have on Oklahoma’s weather isn’t easy to predict, said state climatologist Gary McManus. Depending on the strength of the pattern, it could spell wet weather, dryer weather, or no difference at all, he said.
El Nino patterns typically bring cooler weather and more rain to the Gulf Coast, the desert Southwest and southern California. For example, the record-breaking pattern during the winter of 1997-1998 brought widespread flooding and mudslides to California and the Southwest.
But those heavy rains in the southern United States come at the expense of northern states, which generally see warmer, dryer winters during El Nino years.
The fact that Oklahoma falls squarely between those two regions means the impact of El Nino can be difficult to predict, McManus said. If the pattern is a strong one, it could spell a wet winter in Oklahoma, he said. In 1991 and 1997, strong El Nino patterns brought wetter-than-average weather to the state.
But if this winter’s El Nino is a weak to moderate pattern, as forecasters predict, it could mean a somewhat dryer season than normal, McManus said.
That could be bad news for any farmers in drought-stricken western and southern Oklahoma who were counting on El Nino to bring much-needed rain, he said.
“We’re sort of in the in-between area,” McManus said. “When we talk about El Nino for Oklahoma, strength definitely matters.”