A semi-permanent summertime high-pressure ridge in the vicinity of the New Zealand marine heatwave much of the past 10 years is likely to regenerate during summer 2023-24. Proposed is an added climate diagnostic supporting an anomalous dry and hot summer 2023-24 climate pattern across Australia causing a major drought.

The latest 15-day upper air forecast for the southern hemisphere (by GFS) reveals an amplifying titanic upper-level high pressure ridge developing southwest of South America. Previously, the 2020-23 semi-permanent Amundsen Sea upper trough was “locked-in” the previous 30+ days and responsible in part for a wet pattern for much of Chile, Argentina, and Brazil. The pattern is about to reverse.

During the past 30 days a wet climate has emerged across Brazil, Chile, and eastward across Central Argentina. The wet pattern was somewhat unexpected. The rainy pattern has shifted soil moisture wetter in Central/East-central, and Southeast Brazil and eroded Chile and Argentina drought.

Once again, large marine heatwaves are causal to a catastrophic climate event, this time extreme rainfall in Libya. A large marine heat wave formed off the Northwest Coast earlier this year and recently expanded into the Mediterranean Sea. The upper air pattern associated with the MHW featured an amplified summertime ridge over Europe compensated for by a downstream trough across the east-central Mediterranean Sea. The most recent version of this pattern featured an omega blocking high-pressure centered on Germany.

Meteorological summer 2023 was the 15th hottest on record and included the hottest summer in recorded in history for Louisiana. However, because the hot summer did not strike the Northeast Corridor, the U.S. population weight cooling degree days were greatly diminished. In fact, the last 3 summer seasons were hotter then summer 2023.