El Niño strengthening in Pacific

The global weather phenomenon known as El Niño strengthened last month. Federal forecasters with the National Oceanic and Atmospheric Administration on Thursday increased predictions the pattern will persist through the end of the year.

They also believe the El Niño, which is currently of weak-to-moderate strength, is likely to gain intensity. NOAA is forecasting a greater than 90 percent chance that El Niño will continue through the fall and an 85 percent chance it will last through the winter.

“Things have been evolving nicely. So, so far, no hiccups in the way things are going on. And we also are starting to estimate how strong we think this might become. Right now we slightly favor a strong event by the late fall and winter, but that of course doesn’t rule out weaker type events either," said Mike Halpert, deputy director of NOAA’s Climate Prediction Center.

Historically, strong El Niño events have correlated with average to above-average rain years. 

The June diagnostic is a significant time point for forecasting an El Niño's strength, because predictions become more reliable moving forward.  

“As we get further through the spring into the summer, we kind of get through what we refer to as the spring predictability barrier, which simply means that the forecasts from our computer models have their lowest scale when they’re initiated during the spring. As we get through that, the scale improves and increases,” Halpert said. 

Still need to conserve

Scientists cautioned that even if a strong El Niño develops, it is no guarantee of significant rainfall for drought-parched California.

“All the right numbers are lined up here for a big El Niño that could impact us this winter, but El Niño’s a bad boy and a fickle lover, and he has been known to disappoint more than satisfy," said Bill Patzert, a climatologist with NASA's Jet Propulsion Laboratory at Caltech.

Patzert said even when strong El Niño events do bring significant rainfall, it often occurs in less ideal locations within California. 

"[El Niño] tends to give an extremely wet winter in Southern and Central California but not necessarily Northern California, which is really where we need the snowpack and the rainfall to fill up the great reservoirs and the Sierra Nevadas," Patzert said. 

Patzert said the nature of the current El Niño will be clearer by mid-to-late summer. Scientists said it's likely the event will raise global temperatures. 

"We have a long, hot, dry summer ahead,” he said.