Emerging Kelvin Wave Shifting Eastward: A La Nina Killer!

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Fig. 1: Very warm waters in the subsurface equatorial West Pacific are now shifting eastward well past the Dateline below 100 meters.

Discussion: During quarter 4 of 2020 very warm waters accumulated in both the subsurface and surface of the equatorial West Pacific. During quarter 1 of 2021 the subsurface warmth has shifted gradually eastward past the Dateline in January and reaching almost 120W last week. A Kelvin Wave has emerged (Fig. 1) brought on by a change in the southern oscillation, trade winds and tropical convection. Upper ocean heat east of the Dateline in the equatorial East Pacific has dissipated (Fig. 2). The Kelvin Wave appears headed for the northwest coast of South America which would end La Nina 2020-21. The risk of El Nino emerging in 2021 is (newly) considered. If another Kelvin Wave were to follow later in 2021 an El Nino event becomes likely. Currently, the Nino SSTA regions are neutral to weak La Nina (Fig. 3).

Fig. 2: The east-shifting Kelvin Wave is causing upper ocean heat east of the Dateline to deteriorate.

Fig. 3: The Nino SSTA regions indicated a weak La Nina lingers.