Nov 2021 Climate Forecast Discussion for Dec-Feb through Mar-May
Note:The IRI seasonal forecasts of precipitation and temperature issued this month are based on the NCEP-CFSv2, CanSIPsv2, COLA-RSMAS-CCSM4, and GFDL-SPEAR models. The base period for normal is 1991-2020.
La Niña strengthened during October, with below-average sea surface temperatures (SSTs) evident across most of the equatorial Pacific. The early November CPC/IRI SST forecast in the equatorial Pacific indicates very high probabilities (~ 90%) of La Niña during the Northern Hemisphere winter, but waning gradually to the ENSO-neutral state after February 2022. The four models used in IRI’s seasonal climate forecast all predict cooler than average SST anomalies and an enhanced likelihood of a second La Niña episode (5 consecutive overlapping seasons, according to NOAA’s definition), with significant impacts on the seasonal forecasts of precipitation and temperature across the globe. Both the Atlantic Niño and the negative Indian Ocean Dipole SST patterns have weakened further, and are predicted to return to the neutral state in the coming seasons.
The precipitation forecast for Dec-Feb season shows enhanced probabilities of above-normal precipitation over most of northern South America, southern Africa, and much of the Maritime Continent and Australia. Moderate probabilities of above-normal precipitation are forecasted over and around mainland southeast Asia during Feb-Apr and Mar-May. Consistent with historical La Niña teleconnections, high probabilities of drier conditions are forecasted over most of Mexico, southern and southwestern U.S., southeastern South America, the Middle East, central southwest Asia, and northeast China. These probabilities of below-normal precipitation remain consistent across most of the forecast period, though the probabilities are generally reduced by Mar-May, with the exception of southeastern South America and northeastern Mexico/the southwestern U.S.
Increased probabilities of above-normal temperatures are predicted over parts of southern South America, the U.S., Mexico, Africa, Middle East and Central-South Asia, China, and the Maritime Continent during the whole forecast period. Persistent across the forecast period, high probabilities of below-normal temperatures are forecasted over northwestern Canada, and for Alaska. In addition, slightly below- or near normal temperature probabilities are forecasted over most of northern South America, southern Africa, over and around mainland southeast Asia, and parts of Australia.
