November 2023 Climate Forecast Discussion

Nov 2023 Climate Forecast Discussion for the period Dec-Feb 2024 through Mar-May 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.

In October 2023, sea surface temperatures (SSTs) in the central-eastern equatorial Pacific Ocean were well above the El Niño threshold (the NINO3.4 index value in October 2023 was +1.59 °C), while the weekly-averaged SST anomalies in the NINO3.4 region was +1.80 °C during the week centered on 08 Nov 2023. According to the early-November 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 +1.55 °C for the week ending November 5, 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, and then both gradually weakening towards the end of the forecast period in Mar-May 2024.

Moderately enhanced probabilities of below-normal precipitation are predicted for most of northeastern South America, parts Central America and southern Chile and Argentina, parts of the SE Asia, southern Africa, and some parts of western and northern Australia during the forecast period. A strong tilt of the odds toward above-normal precipitation is predicted over and around the Greater Horn of Africa, the Middle East, the central and South Asia during the forecast period. Moderately enhanced probabilities for above-normal precipitation are also forecasted over and around Uruguay, southern and southeast US, northern and eastern China during the forecast period, though values decrease gradually by the end of the forecast period. Many, though not all, of these precipitation patterns are consistent with historical El Niño as well as 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 weak probabilities for below-normal temperatures over central parts of the US during Dec-Feb, 2024, and for near equal chances of the three temperature tercile categories for much of the United States and northern Eurasia in Jan-Mar, and to a lesser extent in Feb-Apr.