![]() As in March, the April Southern Oscillation Index and the Equatorial Southern Oscillation Index were close to zero, indicating that the Walker circulation remains at near-average strength. How can La Niña seem like a distant memory so quickly?Īlthough the tropical Pacific Ocean looks ready to burst through that door to El Niño, the tropical atmosphere seems a bit more hesitant, remaining firmly in ENSO-neutral territory. Subsurface ocean temperatures in the tropical Pacific also increased over the past month, providing a source of warmer water that can sustain a developing El Niño. This is just a mere 0.1 ☌ away from the 0.5 ☌ threshold that is necessary (but not sufficient!) for declaring El Niño conditions. When we zoom into the weekly time frame, we find that the latest Niño-3.4 measurement from our highest-resolution dataset ( OISSTv2.1) was 0.4 ☌ above the long-term average, even higher than the latest monthly average. NOAA image based on a graph by Michelle L’Heureux and monthly Niño-3.4 index data from CPC using ERSSTv5. This value is up 0.2 ☌ from March and is the first time the monthly Niño-3.4 temperature was warmer than average since April of 2020.ġ6-month history of sea surface temperatures in the Niño-3.4 region of the tropical Pacific for all events evolving into El Niño since 1950 (gray lines) and the current event (purple line). ![]() On the doorstepĪccording to ERSSTv5 (our most consistent historical dataset), the April average sea surface temperature in the Niño-3.4 region (our primary monitoring region for ENSO) was 0.1 ☌ above the long-term (1991–2020) average. We’ll revisit many of these impacts in the coming months, but we’ll start by focusing on all the details of these rapidly developing conditions in the tropical Pacific. We care about the potential development of El Niño-the warm phase of ENSO (El Niño/Southern Oscillation, the whole El Niño-La Niña system)-because of the cascade of global impacts that arise from its occurrence, including the expected temperature and precipitation patterns shown here. ![]() ![]() Consequently, an El Niño Watch remains in place, with El Niño conditions likely to develop within the next couple of months and then persisting ( greater than 90% chance) into the winter. The tropical Pacific sure knows how to get out of a rut! Just two months after declaring the demise of an almost interminable La Niña, above-average surface temperatures have reclaimed the tropical Pacific, and temperatures in the central-eastern Pacific are expected to continue to rise. ![]()
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