Widespread ocean warmth may hamper development
FRISCO — This year’s brewing El Niño may be dampened by widespread warm sea surface temperatures across the Pacific Ocean, according to weather experts. Specifically, ocean temperatures across the far western Pacific have remained so warm that one of the key ingredients for a full-strength El Niño is missing — a significant difference in temperatures between the western and Eastern Pacific.
But so far this summer, warmer than average temperatures are spread across the Pacific from east to west. Just last week, the National Climatic Data Center announced that the average global temperature for June was the warmest on record, driving in large part by warm oceans.
Climate researchers with the National Oceanic and Atmospheric Administration explained the set-up in a pair of blog posts this week, suggesting that, while El Niño conditions are still expected to develop, the intensity is very much in question. El Niño is a phase in rhythmical cycle of changing sea surface temperatures that can have widespread effects on day to day weather in many parts of the world.
When the eastern Pacific is warmer than average and the western Pacific cooler, it drives a change in prevailing wind patterns which reinforces El Niño formation, NOAA climatologist Michelle L’Heureux wrote in a July 25 update, explaining that, for a full-strength El Niño to develop, the ocean and atmosphere may have to be synched. For now, forecasters are closely watching sea surface temperatures around Indonesia to see if the start to drop, which could signal emergence of a stronger El Niño.
In ClimateWatch, NOAA explains the coupling:
During El Niño events, the typical easterly surface winds across the Pacific die down, or sometimes even reverse directions. The reversal in winds happens because the location of the relative low and high pressure areas change places from the west to the east. (Surface winds blow toward low air pressure.)
When those easterly winds abate, it enables even more warm water to pile up in the eastern Pacific, leading to a stronger El Niño event. That warmer water, in turn, drives atmospheric circulation by warming the air and causing it to rise, as NOAA describes it:
Ideally, this warmth would make the overlying air more buoyant, fostering more rising motion in the atmospheric circulation; rising air generates lower surface pressure; lower surface pressure draws the winds.
Bottom line: NOAA is still anticipating El Niño conditions to develop, but it’s anyone’s guess how strong it will be and whether it will last long enough to have a significant effect on winter weather in North America.