Increasing sea temperatures, westerly winds and other factors are pointing to a strengthening El Nino.
Forecasters say there is a 70 percent chance that El Nino — with associated dry conditions in the islands and a higher chance of hurricanes in the eastern and central Pacific — will persist through the summer, and a 60 percent chance those conditions will last through the fall.
Sea surface temperatures have increased across the equatorial Pacific, but particularly along the equator, where temperatures are averaging about 2 degrees Fahrenheit above normal.
Increased westerly winds that carry warmer waters to the east are also indicators of a strengthening El Nino, and forecasters point to a burst of westerly winds along the equator that lasted nine days in March — the longest since 1997. Those westerly winds are a sign the atmosphere is responding to warmer sea temperatures — and increased rainfall near the dateline and reduced trade winds also point to a strengthening El Nino.
Multiple weather models bear out an El Nino gaining force through the summer. But weather scientists hedge away from bold statements about the coming season. We will know much more about the El Nino trend right around the time the Central Pacific Hurricane Center releases its annual hurricane season outlook in late May, meteorologists say.
“(El Nino) has been strengthening quickly very recently, but this does not tell us much for what it will do next month and the month after that,” said Anthony Barnston, an El Nino specialist and chief forecaster for the International Research Institute for Climate and Society at Columbia University, in an email response to questions.
Scientists are cautious in part because very similar El Nino type conditions sprang up in the springtime last year, but the factors never completely came together. The result was weak El Nino-like conditions sputtering along and meteorologists never seeing enough benchmarks to declare a solid event.
There is an important distinction this year, however. The higher sea temperatures along the equatorial Pacific are giving El Nino a higher baseline from which to start.
“The subsurface water temperature along the equator is well above average, providing the potential for above-average surface water temperatures for the next several months,” Barnston said. “But the subsurface water temperature is not a foolproof predictor, because sometimes it can raise the surface water temperature far from the east-central Pacific, such as near the South American coast, giving Ecuador and Peru far above normal rainfall.”
Hawaii has already been seeing El Nino-like effects. Rainfall was down significantly across the island this winter and sea surface temperatures have remained elevated.
Last year’s Eastern Pacific hurricane season was the most active in 22 years and the Atlantic was relatively quiet, in keeping with previous El Nino years.