September 2022 Climate Forecast Discussion

Sep 2022 Climate Forecast Discussion for Oct-Dec through Jan-Mar 2023

Note: The IRI seasonal forecasts of precipitation and temperature issued this month are based on an objective calibration procedure that combines the NCEP-CFSv2, CanSIPS-IC3, COLA-RSMAS-CCSM4, and GFDL-SPEAR, and NASA-GEOSS2S models. The climatological base period for normal is 1991-2020.

In August 2022, the equatorial sea surface temperatures (SSTs) in the central-eastern tropical Pacific Ocean remained cooler than normal, and were consistent with weak La Niña conditions (NINO3.4 index value in August 2022 was -0.96). According to the early-September CPC ENSO forecast, La Niña is likely to persist until boreal winter 2022-23 with 65% probabilities, which would be the first triple-dip event of the 21st century; however, a transition to ENSO-neutral is likely during early boreal spring (56% chance in Feb-Apr 2023). The prolonged La Niña SST pattern in the tropical Pacific does impact the associated seasonal climate forecast. In addition, a negative Indian Ocean Dipole Mode is forecasted for next two (Oct-Dec, and Nov-Jan) overlapping 3-month forecast seasons before transitioning to a neutral state. The tropical Atlantic Ocean exhibits slightly warm SST anomalies.

The precipitation forecast for the Oct-Dec 2022 season show enhanced probabilities of below-normal precipitation over the Middle East and central southwest Asia, eastern Africa, northeast China, over and around Uruguay, southern parts of the US, and most of northern Mexico. These signals continue through rest of the forecast period with generally gradually decreasing strength, except over the southwest US and northern Mexico where they remain strong into Jan-Mar 2023. Increased probabilities of wetter conditions are forecast over the Maritime Continent, much of Australia, as well as less strongly over northern South America, South Africa, parts of Southern Indian Peninsula including Sri Lanka, and over parts of southeast Asia, again generally decreasing in strength through the forecast period. Many, though not all, of these precipitation patterns are consistent with historical La Niña events, again pointing to the important of the SST predictions from these models.

For temperature, enhanced probability of above-normal temperatures is forecasted over much of East Asia, central southwest Asia, large parts of African continent, the Southwest United States, and the southern South America from Oct-Dec 2022 to Jan-Mar 2023. Above-normal to slightly near-normal temperature probabilities are forecasted over the Maritime Continent region during the forecast period. Enhanced probabilities of below-normal temperatures are forecasted for much of Alaska and Canada (particularly in boreal winter), South Africa, over parts of southeast Asia, and much of Australia, during the forecast period. Near-normal to slightly below-normal temperature probabilities are forecasted over most of northern and central parts of South America during the forecast period.