If ENSO Fades Toward La Nina…Great Plains/South America Precipitation Expectations the Next 4 Months.
Discussion: The NINO SSTA regions have cooled significantly in January and are now mostly beneath El Nino thresholds (Fig. 1). During January the subsurface equatorial East Pacific has cooled markedly implying additional cooling at the surface is likely (Fig. 2). During the past 25 years there have been several weak El Nino events suddenly fading during mid-northern hemisphere winter (Fig. 3). Each analog continued to cool through following summer to neutral ENSO phase with 3 of 4 analogs maintaining that thermal descent into La Nina later that year. The consensus of dynamic and statistical models is less respectful of the observational cooling which is developing in January. Dynamic and statistical models carry El Nino into northern hemisphere summer with an uncertain wide spread in possibilities for later this year (Fig. 4).
Because of the observational trend out of El Nino more quickly than expected and the historical precedent for additional backing away from El Nino to be replaced by a possible La Nina later this year a look at the FEB-MAY precipitation pattern across the Great Plains and Argentina/Brazil is provided.
In the U.S. a wetter-than-normal regime is indicated across the Great Plains while the Missouri/Ohio Valley are drier than normal (Fig. 5). If an active MJO is present which is typical during a non-El Nino regime the indicated precipitation anomalies could be more extreme. In South America the analog prediction indicates dryness in Paraguay plus Mato Gross Do Sul while Mato Grosso toward Bahia is wetter than normal (Fig. 6).
Fig. 1: The Nino SSTA regions have cooled to neutral ENSO in January.
Fig. 2: The story of a failed El Nino in the equatorial East Pacific is told by subsurface temperature anomalies which suddenly faded cool during January.
Fig. 3: During the past 25 years 4 weak/short duration El Nino’s have also weakened suddenly during mid-northern hemisphere winter. A trend toward La Nina followed (except in 2003).
Fig. 4: A collection of ENSO phase forecast models by the International Research Institute for Climate and Society.
Fig. 5: The FEB-MAY 2019 analog precipitation potential for the Great Plains.
Fig. 6: The FEB-MAY 2019 analog precipitation potential for Brazil and Argentina.