July 2023 Climate Forecast Discussion

Jul 2023 Climate Forecast Discussion for the period Aug-Oct through Nov-Jan 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 June 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 June 2023 was +0.88 °C). Weekly-averaged SST anomalies in the NINO3.4 region have warmed further and reached +1.0 °C during the week centered on 05 July 2023. According to the early-July CPC ENSO forecast, the tropical Pacific is experiencing El Niño conditions and 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 positive Indian Ocean Dipole is predicted to develop in Aug-Oct, and continue during the boreal fall.

Strongly or moderately 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 of below-normal precipitation are also forecasted for South Africa, the Congo basin and central north-eastern Europe during Oct-Dec 2023 and Nov-Jan 2024. A strong tilt of the odds toward above-normal precipitation is predicted for the Greater Horn of Africa and the Middle East during the forecast period. Gradually increasing probabilities for above-normal precipitation are also forecasted over and around Uruguay, southeast US, Alaska, eastern Greenland during 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.

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 during the forecast period, notable over southeast Madagascar.