During the 30-day period of Oct. 12-Nov. 11, 2024, an unusually hot climate spread across most of Australia featuring widespread 30-day departures from normal of +2C to +5C. The anomalous heat is driven by a titanic upper-level high-pressure ridge centered on central continent. The catalyst to the upper ridge, in-part, is due to warming influence on the middle troposphere by the presence of an emerging large and strong marine heatwave (MHW) off the northwest coast of Australia.

The long-term cycle of the Atlantic multi-decadal oscillation (AMO) shifted to the warm phase in the mid-to-late 1990’s. The tendency for a consistent warm phase increased in the 2 decades to follow. However, the recent warming, especially in the current decade has reached “excessive warm” values.

An expanding Northern Eurasia snow cover cools the atmosphere aloft and forces a broad low-pressure trough during mid-November. To compensate, a ridiculously resilient ridge (RRR) stays intact across eastern North America and Western Europe enhanced by lack of snow cover and a marine heat wave (MHW) west of Europe.

The Australia Bureau of Meteorology adds the following statement to their ENSO outlooks: “Global SSTs remain at near record levels, with temperatures since July being just short of the record temperatures observed during 2023, yet above all other years since observations began in 1854. The sustained nature of this significant global ocean heat suggests that climate indicators such as ENSO and IOD may not behave or evolve as they have in the past.”