Jun 2023 Climate Forecast Discussion for Jul-Sep through Oct-Dec 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. The SST anomalies cited below refer to the OISST.v2.1 SST data set.
In May 2023, equatorial sea surface temperatures (SSTs) in the central-eastern equatorial Pacific Ocean were close to the borderline of El Niño (the NINO3.4 index value in May 2023 was +0.47 °C). The current SST anomalies in the region have reached the El Niño threshold on a weekly basis (as of the week of 07 Jun, the NINO3.4 index was +0.9 °C). Based on the early-June CPC ENSO forecast, the tropical Pacific is experiencing El Niño conditions and therefore an El Niño Advisory has been issued. Both observations and model forecasts indicate the presence of mild warm SST anomalies in the Atlantic Ocean, and a slightly positive Indian Ocean Dipole is predicted to develop in Jul-Sep, and to strengthen to become moderately strongly positive by Oct-Dec 2023.
Strongly enhanced probabilities for below-normal precipitation are predicted for northern South America, the Maritime Continent, and most of Australia during the forecast period. Enhanced probabilities for above-normal precipitation are predicted for most of African Sahel and Gulf of Guinea, northwest parts of Africa, Southern Indian Peninsula, Sri Lanka, Southern Madagascar, as well as the southeast US and Caribbean during the forecast period. A strongly strengthening tilt of the odds toward above-normal precipitation are predicted for Greater Horn of Africa and the Middle East during Aug-Oct through Oct-Dec. Enhanced probabilities for above-normal precipitation are also predicted over and around Uruguay and Alaska during Sep-Nov, and Oct-Dec 2023. Many, though not all, of these precipitation patterns are consistent with historical El Niño events.
For temperature, strongly enhanced probabilities for above-normal temperature are forecasted over most land areas throughout the forecast period, consistent with the impacts of El Niño combined with anthropogenic global warming. Enhanced probabilities for below-normal temperature are relatively scant, but do appear locally over Colombia and northeast Brazil, parts of Madagascar, and southeastern parts of Australia, small northwestern parts of Canada, and central northwest Asia.
