May 2024 Climate Forecast Discussion

May 2024 Climate Forecast Discussion for the period Jun-Aug 2024 through Sep-Nov 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-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

During April 2024, there was a further decline 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 +0.81 °C. The weekly-averaged SST anomalies in the NINO3.4 region were +0.30 °C for the week centered on May 08, 2024. According to the early-May CPC ENSO forecast, both a current El Niño Advisory and a La Niña watch for boreal summer and fall remain in place. The Indian Ocean Dipole (IOD) index is currently neutral with the most recent value of +0.22 °C for the week ending May 12, 2024, according to the Australian Bureau of Meteorology. 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 be remain in the neutral state, with a developing a La Niña SST anomaly pattern over the tropical Pacific.

IRI’s seasonal precipitation forecasts issued in May show elevated probabilities of above-normal precipitation in various regions during the forecast period, 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 most parts of Australia. The forecast shows elevated probabilities of below-normal precipitation over the northern parts of South America during Jun-Aug, and Jul-Sep, 2024, which fades away during the last two seasons in forecasts in the northern regions, while gradually strengthen in the southern parts of South America in Aug-Oct, and Sep-Nov, 2024. There is a gradual leaning towards below-normal precipitation over the southern US and Mexico starting from Jun-Aug 2024 to the end of the forecast period. 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 the boreal summer of 2024.

Regarding temperature, strongly enhanced probabilities for above-normal temperature are forecasted across most land areas throughout the forecast period. In the southern parts of South America, and southern regions of Australia, the forecast show increased probabilities for below-normal temperatures during Jun-Aug, and Jul-Sep 2024. The parts of northeast Africa, Sahel, Southwestern Arabian Peninsula, and parts of South Asia, also shows weak probabilities for below-normal temperatures during Jun-Aug, and Jul-Sep, consistent with the above-normal forecasts of precipitation during the summer monsoon time.