13 August 2015 (Climate Central) – This year’s El Niño is poised to join the ranks of the strongest such events on record, U.S. forecasters said Thursday, with potentially significant impacts for weather across the country this winter.
“We’re predicting that this El Niño could be among the strongest El Niños in the historical record dating back to 1950,” Mike Halpert, the deputy director of the Climate Prediction Center, part of the National Oceanic and Atmospheric Administration, said during a press teleconference.
Whether this is good news or bad news depends on where you are: For Californians, the prospect of a top-tier El Niño boosts the hopes for a wetter-than-average winter, which is desperately needed after four years of record-setting drought. For the Pacific Northwest, also mired in drought, El Niño usually means drier weather, though it could still be an improvement on last year.
El Niño is a cyclical climate phenomenon rooted in the tropical Pacific that features a buildup of warmer-than-normal waters in the central and eastern portions of the basin. Over the last few months, those waters have been steadily heating up. In July, temperatures in a key region were more than 2°F above average, a departure that comes in second only to the blockbuster El Niño of 1997-1998, the event by which all other El Niños are judged.
It’s possible this El Niño, which in the latest update was called “significant and strengthening,” could reach more than 3.5°F above normal in this ocean region, “a value that we’ve only recorded three times in the last 65 years,” Halpert said. That threshold was reached during the 1997-1998 event, as well as those from 1982-1983 and 1972-1973. [more]
Synopsis: There is a greater than 90% chance that El Niño will continue through Northern Hemisphere winter 2015-16, and around an 85% chance it will last into early spring 2016.
During July, sea surface temperatures (SST) anomalies were near +1.0oC in the central equatorial Pacific Ocean, and in excess of +2.0oC across the eastern Pacific (Fig. 1). SST anomalies increased in the Niño-3 and Niño-3.4 regions, while the Niño-4 and Niño-1+2 indices decreased slightly during the month (Fig. 2). Positive subsurface temperature anomalies strengthened in the central and east-central equatorial Pacific during the month (Fig. 3), in association with the eastward movement of a downwelling oceanic Kelvin wave (Fig. 4). The atmosphere remained coupled to the oceanic warming, with significant low-level westerly wind anomalies continuing from the western to east-central equatorial Pacific, along with anomalous upper-level easterly winds. Also, the traditional and equatorial Southern Oscillation Index (SOI) were both negative, consistent with enhanced convection over the central and eastern equatorial Pacific and suppressed convection over Indonesia (Fig. 5). Collectively, these atmospheric and oceanic features reflect a significant and strengthening El Niño.
All models surveyed predict El Niño to continue into the Northern Hemisphere spring 2016, and all multi-model averages predict a strong event at its peak in late fall/early winter (3-month values of the Niño-3.4 index of +1.5oC or greater; Fig. 6). At this time, the forecaster consensus unanimously favors a strong El Niño, with peak 3-month SST departures in the Niño 3.4 region potentially near or exceeding +2.0oC. Overall, there is a greater than 90% chance that El Niño will continue through Northern Hemisphere winter 2015-16, and around an 85% chance it will last into early spring 2016 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).
Across the contiguous United States, temperature and precipitation impacts associated with El Niño are expected to remain minimal during the remainder of the Northern Hemisphere summer and increase into the late fall and winter (the 3-month seasonal outlook will be updated on Thursday August 20th). El Niño will likely contribute to a below normal Atlantic hurricane season, and to above-normal hurricane seasons in both the central and eastern Pacific hurricane basins (click Hurricane season outlook for more).
This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA's National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum of CPC's Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog. The next ENSO Diagnostics Discussion is scheduled for 10 September 2015. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: email@example.com.
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