There is also a large pool of cooler-than-average water under the surface, adding confidence that La Niña’s demise is not imminent.įorecasters think the most likely scenario is for La Niña to transition to neutral by the late spring. Forecasters are confident that La Niña will continue for the next few months, partly based on computer model predictions. This is according to ERSSTv5, our most reliable dataset, and comfortably within the La Niña category of more than 0.5 ☌ cooler than average. The sea surface temperature in the Niño-3.4 region of the tropical Pacific, our primary ENSO monitoring index, was about 0.9 ☌ cooler than the long-term (1991–2020) average. These waves move relatively quickly, so they usually don’t show up in monthly or seasonal sea surface temperature maps. Any time there is a temperature difference, or gradient, between cold and warm, nature wants to smooth it out, and tropical instability waves help to mix the cooler equatorial surface with the warmer off-equatorial water to the north and south.ĭuring La Niña, the cold tongue is even colder (shudder), so we often see prominent tropical instability wave action. (Scientists refer to this region as the “cold tongue,” unfortunately.) This cooler surface right along the equator is due to cold water upwelling from the deep ocean. The equatorial eastern Pacific is usually cooler than the water just to the north and south, and cooler than the water in the far western Pacific. The wavy features in the animation above are called tropical instability waves. Also characteristic of La Niña is the warmer-than-average surface temperatures in the far western Pacific. Over the past few weeks, cool anomalies have increased in the eastern Pacific, and in general we see a well-established La Niña pattern. La Niña’s hallmark cooler-than-average ocean surface is readily apparent across much of the tropical Pacific.
Description of historical baseline period here. Graphic by, based on data from NOAA’s Environmental Visualization Lab. Sea surface temperature difference from the long-term average from mid-October 2021 to early December.
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