August 2021 Climate Forecast Discussion for Sep-Nov through Dec-Feb 2022
The IRI NMME seasonal forecast for Aug 2021 uses 3 models, CanSIPSv2, NCEP-CFSv2, and COLA-RSMAS-CCSM4.
The SST temperatures in the tropical Pacific are slightly cooler than normal, and ENSO-neutral conditions are in place. Forecasts from the North American Multi-Model Ensemble (NMME) predict that SSTs will continue to cool and produce a second La Nina event over the next several seasons. SST anomalies in equatorial Atlantic are above-normal in the strongest Atlantic Nino ever observed. The equatorial Atlantic SSTs are likely to remain above-normal through the boreal summer. SST anomalies in Indian ocean are also above-normal, and these also are predicted to persist through the rest of the boreal summer.
The precipitation forecast shows enhanced probability for above-normal rainfall over parts of the Maritime continent, eastern Brazil, and much of Australia during the next four seasons, though the probabilities are much weaker by DJF. The seasonal precipitation forecasts favor below-normal precipitation for the band extending from Senegal to southern Sudan during the SON season. During the first two seasons (SON and OND), precipitation is also forecast to be below-normal over much of the Greater Horn of Africa countries, Uruguay, southern Argentina and Brazil, and northern Europe. In OND the southeastern United States and southwestern Asia also show forecasts favoring below-normal precipitation. The southeastern US region favoring below-normal precipitation evolves in the following seasons – first to Texas and northern Mexico, and then encompassing the southwest.
Surface temperatures over southern/mideastern United States are likely to be above-normal for the SON season, and subsequently evolves toward Texas and northern Mexico, and then across the southern tier of the US. Above-normal temperatures are forecast over northern Asia for all seasons. Below-normal temperatures are forecast for northern Canada in NDJ, and that below-normal forecast area grows in DJF to include most of Canada, Alaska, and north-central US.
