Jun 2024 Climate Forecast Discussion for the period Jul-Sep 2024 through Oct-Dec 2024
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-CESM1, 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.
Starting from June 2024, the observed climatology used to compute the dry mask was updated to 1991-2020, and the criterion modified to mask points where 10% of the training sample (I.e. 3 or more years) received less than or equal to 1 mm over a 3-month season.
During May 2024, there was a further weakening in the sea surface temperatures (SSTs) within the central-eastern equatorial Pacific Ocean compared to the preceding month, leading to a NINO3.4 anomaly index value of +0.31 °C. The weekly-averaged SST anomalies in the NINO3.4 region were +0.10 °C for the week centered on June 05, 2024. This shows the end of the 2023/24 El Niño and return of the ENSO-neutral state in the equatorial Pacific Ocean. According to the early-June CPC ENSO forecast, both a Final El Niño Advisory and a La Niña watch for boreal summer and fall were issued. The Indian Ocean Dipole (IOD) index is currently neutral. The North Atlantic Ocean continues to exhibit persistent warm SST anomalies. Forecasts indicate that the warming in the North Atlantic Ocean will continue for the next couple of months while the Indian Ocean Dipole is forecasted to remain in the neutral state, with a developing La Niña SST anomaly pattern over the tropical Pacific.
IRI’s seasonal precipitation forecasts issued in Jun, 2024 show elevated probabilities of above-normal precipitation in various regions during the first two seasons of forecast period (Jul-Sep, and Aug-Oct, 2024), including Central America, and Caribbean regions, Sahel, northeast Africa, and Southwestern parts of the Arabian Peninsula, South Asia, the Maritime Continent regions, parts of China and Australia. The forecast shows elevated probabilities of below-normal precipitation over different parts of South America during the forecasts period. The shift the probabilities towards below-normal is particularly strong over and around Uruguay. The forecast shows strong probability of below-normal precipitation over the western and central parts of CONUS, in Jul-Sep and Aug-Oct, 2024, while during Sep-Oct, and Oct-Dec, most of the southern parts of the CONUS, show a strong shift below-normal signal, while a weak spotty above-normal probabilities appear over the northern parts. There is a gradual leaning towards below-normal signal over the Middle-East starting from Jul-Sep 2024, which becomes particularly strong by the end of the forecast period (Oct-Dec). Many, while not all of these precipitation patterns align with historical La Niña events, many of them do, which is in line with the forecasted onset of La Niña from Jul-Sep, 2024.
Regarding temperature, strongly enhanced probabilities for above-normal temperature are forecasted across most land areas throughout the forecast period. The forecast shows elevated probabilities of below-normal temperatures over southeastern parts of Australia during Jul-Sep, 2024, which is forecasted to get weaken in Aug-Oct, and fades away in Sep-Nov, 2024. The forecast indicates a tilt towards normal temperature over parts of western Australia in Oct-Dec, 2024. The forecasts show Climatological odds for the parts of monsoon region in African Sahel and South Asia during Jul-Sep, and Aug-Oct, 2024.
