Island Climate Update 221 - February 2019
Over the past month, sea surface temperatures (SSTs) in the central Pacific have remained above normal particularly near and west of the International Dateline, although declined slightly below the conventional threshold for El Niño.
The Southern Oscillation Index (SOI) decreased substantially from a positive value of +0.8 during December to -0.1 during January (in the neutral range). Trade winds were close to normal east of the International Dateline during January 2019, however a westerly wind burst earlier in January in the far western Pacific triggered warming at depth (100-150 m) near and just east of the International Dateline.
The atmosphere has responded to the warm pool of water in the central and western Pacific, but the coupling between the ocean and the atmosphere still remains weak. During traditional El Niño events, this response tends to take place farther east and is usually well-established by this time of year. It appears quite unlikely that a classical coupling will occur over the next 3 months.
The probability for oceanic El Niño conditions, according to the consensus from international models, is 74% over February – April period. Compared to last month, the probabilities decreased for April - June 2019 (now 65%, down from 78%) and August - October 2019 (now 51%, down from 62%).
However, later in 2019, long-range models indicate the potential re-emergence of oceanic El Niño conditions, which suggests the potential for a ‘protracted’ event. This means that above average SSTs may persist for more than a year across the equatorial Pacific.