Dec 2021 Climate Forecast Discussion for Jan-Mar through Apr-Jun 2022
Note: The IRI seasonal forecasts of precipitation and temperature issued this month are based on the NCEP-CFSv2, CanSIPS-IC3, COLA-RSMAS-CCSM4, and GFDL-SPEAR models. Starting from Dec 2021, a new CanSIPS-IC3 model replacing the CanSIPSv2 model has been used in NMME seasonal forecasts. The climatological base period for normal is 1991-2020.
In November 2021, the sea surface temperatures (SSTs) anomalies in the tropical Pacific were well-below La Niña thresholds. The early December CPC/IRI ENSO forecast indicates very high probabilities of La Niña during the Northern Hemisphere winter, weakening gradually, and likely to dissipate in Mar-May 2022 (50%). The three out of four models (except GFDL-SPEAR) used in IRI’s seasonal climate forecast predict cooler than average SST over the eastern tropical Pacific with a continuation of the La Niña episode (5 consecutive overlapping seasons, according to NOAA’s definition); this has 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 strengthened during November, although the forecast shows their dissipation in the coming months.
In Jan-Mar, strongly enhanced probabilities of below-normal precipitation are forecast for northwest Mexico and the Southern US; these persist through the rest of the forecast period with northward movement and gradually weakened values. Moderate probabilities of above-normal precipitation are forecast for northern South America, Central America, the Philippines, northwest US, some scattered regions of Africa, and Australia during Jan-Mar and the rest of the forecast period. Moderately enhanced probabilities of below-normal precipitation are forecast in Southwest Asia during Feb-Mar, and onwards. In Feb-Mar and onwards, weak to moderate probabilities of above-normal precipitation are forecast over Southeast Asia to central China.
For temperature, the increased probabilities of above-normal temperatures are forecast over most land areas, with particularly enhanced probabilities over the Maritime Continent, Asia, the Middle East, large parts of the African continent, much of North America, eastern Canada, and southern South America. For the last two seasons (Feb-Apr, and Apr-Jun), the temperature forecast over most of these regions even show the enhanced likelihood for above-average conditions. Strongly enhanced probabilities of below-normal temperatures are forecasted over Pacific northwest, southwestern Greenland, Madagascar, southern parts of the Indian Peninsula, and some isolated parts of western Australia during Jan-Mar and onwards, although weakening gradually toward the end of the forecast period.
