Dec 2023 Climate Forecast Discussion for the period Jan-Mar 2024 through Apr-Jun 2024
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. The SST anomalies cited below refer to the OISST.v2.1 SST data set.
During November 2023, the sea surface temperatures (SSTs) in the central-eastern equatorial Pacific Ocean exceeded the threshold for a strong El Niño event, with the NINO3.4 index reaching +1.90 °C. The weekly-averaged SST anomalies in the NINO3.4 region remained at +1.90 °C for the week centered on December 6, 2023. According to the early-December CPC ENSO forecast, the tropical Pacific is experiencing El Niño conditions and an El Niño Advisory remains in place. The ongoing positive Indian Ocean Dipole (IOD) event persists with the IOD index recorded at +1.20 °C for the week ending December 03, 2023, according to the the tropical Pacific is experiencing El Niño conditions and an El Niño Advisory remains in place. The ongoing positive Indian Ocean Dipole (IOD) event persists with the IOD index recorded at +1.20 °C for the week ending December 03, 2023, according to the Australian Bureau of Meteorology. The North Atlantic Ocean also exhibits persistent warm SST anomalies. Forecasts indicate that the warming in the North Atlantic Ocean and the positive Indian Ocean Dipole are expected to persist into Dec-Feb 2024, with both subsequently gradually weakening to become neutral in or around March 2024.
Elevated probabilities of below-normal precipitation are predicted in various regions, including northeastern South America, areas in Chile and Argentina, southern Africa, portions of Southeast Asia, the Philippines, and certain parts of western and northern Australia across the forecast period. In the Northwest US and western Canada, there is a slight leaning towards below-normal precipitation during the forecast period. Enhanced probabilities of above-normal precipitation are expected in and around the Greater Horn of Africa, parts of central and South Asia, as well as over parts of northern South America from Feb-Apr onwards. There are weaker probabilities for above-normal precipitation likely over and around Uruguay, the southern and southeastern US, and northern and eastern China during the forecast period, with values gradually diminishing towards the end of the forecast period. In the Feb-Apr, Mar-May, and April-June, the forecast show moderate probabilities of above-normal precipitation over the central America, and the northern and northwestern parts of South America. In the Mar-May and Apr-Jun 2024, there are progressively heightened probabilities of above-normal precipitation over the Maritime Continent region, as well as in the southern and southeastern parts of Australia, which could be associated with the ENSO transition phase during these times, shifting from warm to ENSO-neutral conditions. It is noted that many, though not all, of these precipitation patterns align with historical El Niño and positive Indian Ocean Dipole events.
Regarding temperature, strongly enhanced probabilities for above-normal temperature are forecasted across most land areas throughout the forecast period. A few local instances of enhanced probabilities for below-normal temperature do appear locally, most notably over southern half of Madagascar throughout the forecast period. The forecast indicates climatological odds (near equal chances of the three temperature tercile categories) for much of the United States, and parts of northern South Asia in Jan-Mar, and to a lesser extent in Feb-Apr. The forecast also indicates weak probability tilts toward below-normal temperatures over scattered regions in southern Australia during Mar-May, and Apr-Jun, 2024.
