La Nina Roars Into Early 2021

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11/09/2020, 9:49 am EST
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La Nina 2020-21 appears projected to be almost as strong as the 2007-08 episode ranking the event 3rd strongest of this century so far. The Climate Impact Company analog projection is based on 3 cold ENSO events from the past 25 years and the consensus projects peak intensity in January, weakening La Nina next spring, neutral ENSO next summer and possible return to weak La Nina DEC/JAN/FEB 2021-22.

Highlight: Moderate-to-strong La Nina into early 2021.

Discussion: La Nina 2020-21 appears projected to be almost as strong as the 2007-08 episode ranking the event 3rd strongest of this century so far. The Climate Impact Company analog projection is based on 3 cold ENSO events from the past 25 years and the consensus projects peak intensity in January, weakening La Nina next spring, neutral ENSO next summer and possible return to weak La Nina DEC/JAN/FEB 2021-22 (Fig. 1). A collection of all dynamic and statistical models provided by the International Research Institute for Climate and Society indicates peak intensity DEC/JAN/FEB 2020-21weakening to neutral phase by APR/MAY/JUN 2021 (Fig. 2).

Fig. 1: The Climate Impact Company ENSO analog projection through 2021.

Fig. 2: A collection of ENSO forecasts using the Nino34 SSTA index from the International Research Institute for Climate and Society.

The key predictor of ENSO phase/intensity is usually the subsurface waters of the eastern equatorial Pacific Ocean. The 4-month trend of equatorial Pacific Ocean subsurface temperatures was emerging cool waters last August strengthening during September/October to initiate La Nina and offering plenty of cool fuel to keep La Nina going well into 2021 (Fig. 3).

La Nina climate during DEC/JAN/FEB historically brings wet conditions to Indonesia which can easily extend to Southeast Asia and Australia (Fig. 4). Additionally, wet climate is likely across the north coast of South America while southeast Brazil observes a cooler than normal summer. South Africa enjoys a cool and wet summer season. In the northern hemisphere dryness dominates China and the southern U.S. while encouraging cold air masses to gather in Western Canada which extend to the northern U.S. The Northwest U.S. is generally wetter than normal.

Fig. 3: Subsurface equatorial Pacific Ocean temperature anomalies for the past 4 months provided by Australia Bureau of Meteorology.

Fig. 4: Global climate anomalies produced by La Nina during DEC/JAN/FEB according to NOAA.