Weekly ENSO Dignostics Report

U.S. Summer 2019 is 13th Warmest on Record
09/08/2019, 1:38 pm EDT
An Exceptionally Warm September 2019
09/10/2019, 1:35 pm EDT
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NCEP CFS V2 Returns Weak El Nino in DEC/JAN/FEB 2019-20

Fig. 1-2: The Nino34 SSTA 12-week trend is into neutral ENSO while the previous El Nino Modoki index is also easing.

Fig. 3: The NCEP CFS V2 global SSTA forecast for DEC/JAN/FEB 2019-20 suddenly reverses their ENSO forecast as a weak El Nino is now indicated.

Discussion: ENSO is in neutral phase. The Nino SSTA regions over the past 12 weeks indicate a borderline weak El Nino (using the Nino34 SSTA) fading to slightly cooler than normal the past 2 weeks (Fig. 1). Additionally, the El Nino Modoki index fades from the positive phase to weak regime during the past week (Fig. 2).

In a bit of a twist the NCEP CFS V2 global SSTA forecast for DEC/JAN/FEB 2019-20 indicates regenerating El Nino (Fig. 3). The forecast has support in that a moderately strong warm phase of the Pacific decadal oscillation persists. Normally, presence of +PDO implies El Nino is also present or about to form. Conversely, the subsurface equatorial Pacific has trended much cooler in early September. The subsurface trend supports La Nina.

Summary: ENSO is in neutral phase. Forecast confidence for the 2020 ENSO phase is below average. NCEP CFS V2 indicates returning weak El Nino.