La Nina Forecasts Popping Up

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Highlight: La Nina forecasts popping-up

Fig. 1-2: The NCEP CFS V2 Nino34 SSTA forecast indicates La Nina developing by AUG/SEP/OCT 2020. The GFDL also projects weak La Nina by MAY/JUN/JUL 2020.

Discussion: In a bit of a surprise some global forecast models are indicating risk of weak La Nina developing during or just-after mid-2020. The NCEP CFS V2 forecast indicates La Nina-like Nino34 SSTA emerging by late summer and strengthening during autumn (Fig. 1). The GFDL global SSTA forecast indicates weak La Nina developing more quickly by late spring and early summer (Fig. 2). If a weak La Nina appears during the 2020 North Atlantic tropical cyclone season given the warm SSTA forecast for the North Atlantic basin watch out! A very active tropical cyclone season including land-threatening hurricanes could occur.

Not all models agree on the weak La Nina for mid-to-late 2020. Currently, the equatorial East Pacific is marginally warm and has a weak El Nino look. Subsurface temperatures indicate east-shifting warmth to the east of the Dateline which could encourage more El Nino-like warming. The models are indicating while additional short-term warmth is possible after that risk the long-term trend is cooling of the equatorial East Pacific.