Executive Summary: The Australia season 1-3 ahead forecast is updated valid for meteorological autumn 2023 through meteorological spring 2024. The forecast is based on evolving +IOD and El Nino climate enhanced by the influence of subtropical ridging associated with marine heatwaves located either side of the continent. The result is a significant drought across East Australia for the summer season ahead. Climate: Current soil moisture conditions reveal the onset of an anticipated major drought for summer 2023-24 as soil moisture conditions have turned considerably drier in the East and Southwest Australia according to NOAA/CPC (Fig. 1). The 30-day upper air pattern reveals a robust subtropical high-pressure area stretching across Australia from New Zealand causing early season excessive heat and attendant dryness (Fig. 2). The high-pressure ridge is associated with a semi-permanent marine heatwave (MHW) in the vicinity of New Zealand (Fig. 3). Additionaly, increased tendency for subtropical ridging from the west where a second marine heatwave is present in the South Indian Ocean can also occur at times. The drying influence too west and south Australia by a developing positive phase Indian Ocean dipole (+IOD) is evolving. An added dry influence for Eastern Australia has developed due to El Nino. A look at the North America multi-model ensemble (NMME) global SSTA forecast for FEB/MAR/APR 2024 reveals an evolving +IOD pattern during Q4/2023 reaches mature stage with widespread tropical Indian Ocean warming while the robust 2023-24 El Nino also continues (Fig. 4). Both regimes are likely dry influences on Australia climate. In addition, drying subtropical high-pressure ridging is enhanced due to the marine heatwaves on either side of Australia. Drying climate influences of +IOD, El Nino, and MHW’s are likely through the 2023-24 warm season across Australia. While large areas of warm SSTA in the subtropics/middle latitudes increase the risk of high-pressure ridging and attendant dry and hot weather risk, keep in mind that any synoptics storms or tropical cyclones moving across warmer than normal ocean waters can lead to excessive short-term rainfall events. Fig. 1: Daily soil moisture anomaly analysis across Australia. Fig. 2: The prevailing upper air pattern for the past 30 days. Fig. 3: Current global SSTA analysis. Fig. 4: The NMME global SSTA forecast for FEB/MAR/APR 2024. Methodology: The Australia season 1-3 ahead climate forecast is generated using a constructed analog based on regional SSTA patterns (IOD, ENSO, and MHW’s) and their correlating upper air patterns that generate the sensible weather pattern. JUN/JUL/AUG 2023 verification: The CIC-CA forecast for Australia winter featured cold risk across Southern Australia and warm risk in the Northeast (Fig. 5). The precipitation forecast was mostly seasonably dry (Fig. 6). The verification of temperature indicates a much warmer regime across Central and East Australia while the West and Southwest were temperate (Fig. 7). The winter precipitation regime was dry on each coast enabling drought development (Fig. 8). Fig. 5-8: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for JUN/JUL/AUG 2023 and observed weather for comparison purposes. SEP/OCT/NOV 2023: During springtime, the prevailing upper air pattern features an amplified upper ridge off the southeast coast of Australia and related to the New Zealand MHW. The sensible weather pattern favors anomalous heat in Southeast Australia with warmer than normal conditions for most of the continent. Dryness is dominant across much of Eastern Australia where drought is likely to expand. The northern continent is also drier than normal. Fig. 9-10: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for SEP/OCT/NOV 2023. DEC/JAN/FEB 2023-24: During summertime, the subtropical ridge associated with the South Indian Ocean MHW extends eastward across Australia. The New Zealand upper ridge shifts eastward and away from the East Australia coast. Favored is anomalous heat across much of the continent most confidently forecast in the Northwest but also present in Southeast Australia. Dryness is dominant in the East where drought worsens. The upper coast of Western Australia is cool due to cool SSTA just offshore. Strong East Australia drought is underway! Fig. 11-12: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for DEC/JAN/FEB 2023-24. MAR/APR/MAY 2024: Next autumn remains warmer than normal across much of Australia. Some relief from tropical cyclones to bring rain in Queensland is indicated. A strong drought across New South Wales to Victoria is likely to continue. Drought is also present across much of Western Australia. Fig. 13-14: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for MAR/APR/MAY 2024.