11/17/2023, 10:20 am EST

Australia Month 1-3 Ahead Outlook: Widespread anomalous heat for summer ahead; Driest climate west and northwest continent.

Executive Summary: The Climate Impact Company month 1-3 ahead climate forecast valid for meteorological summer 2023-24 for Australia is updated. The outlook is hotter than normal for most of the continent with +IOD/El Nino-inspire drought stretched across northwest continent. Parts of the East Coast also encounter drier than normal climate.  Due to some early summer rainfall related to a climate pattern inspired by a marine heatwave in the South Pacific, drought concerns across Eastern Australia are slowed. West/southwest Australia become the primary drought targets for summer 2023-24. Fig. 1-2: The Climate Impact Company meteorological summer temperature and precipitation anomaly forecast for Australia. Climate: Moderate-to-strong El Nino and an amplified positive phase of the Indian Ocean dipole (+IOD) are present. However, despite the strong historical influence on Australia climate of these two climate diagnostics, another feature is bringing unexpected climate to Australia as meteorological summer approaches. In the South Pacific, present since late last year, a strong marine heat wave (MHW) stretches from east of Madagascar to near 40S due south of India (Fig. 3). During the past 90 days, an amplified upper-level high-pressure ridge is located downwind the MHW regime and located over Southwest Australia (Fig. 4). During AUG/SEP/OCT, very dry climate emerged across Southwest and East Australia leading to developing drought in each region. The upper ridge spawned +4C temperature anomalies for Interior Western Australia during this period with +2C anomalies across Interior East Australia. The dry and warmer than normal climate pattern is changing. The upper-level high-pressure ridge is shifting southwestward (Fig. 5). A compensating upper trough is forming over Australia and an unexpected very wet pattern already underway in Australia will continue into December (Fig. 6). The ECMWF global SSTA forecast valid for January 2024 indicates strengthening El Nino and +IOD in the tropics (Fig. 7). Additionally, the South Indian Ocean MHW also strengthens and expands toward Australia and becomes a 3rd heavily weighted influence on summertime Australian climate. Fig. 3-4: Daily global SSTA analysis and regions of influence on Australia climate plus the 90-day 500 MB anomaly analysis for the South Indian Ocean and Australia. Fig. 5-6: ECM ENS 15-day 500 MB anomaly and percent of normal rainfall projection across Australia. Fig. 7: ECMWF global SSTA forecast for January 2024. December 2023: December certainly begins wet in the East. However, based on the constructed analog and ECMWF “weeklies” a drier pattern follows. Already established during late spring is the tendency for anomalous heat over Western Australia. After the wet start to the month, a drier/hotter regime will spread across Southern Australia mid-to-late month. The forecast has similarities to the previous outlook with the exception of the wet start to the month. Fig. 8-9: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for December 2023.  January 2024: During mid-summer, a drier than normal monsoon season stretches across the northern continent. The forecast trend is drier compared to the previous outlook. The only wet zone is in the coastal southeastern sections. Hottest anomalies are across Northwest and Southeast Australia. Overall, the January 2024 temperature anomaly outlook eases back slightly. Fig. 10-11: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for January 2024.  February 2024: The late meteorological summer outlook is consistent with the previous forecast offering anomalous heat and dry risk across west and northwest continent. The southeast sector of Australia is normally hot with near normal rainfall. Fig. 12-13: The Climate Impact Company constructed analog temperature and precipitation anomaly climate forecasts for February 2024.