During AUG/SEP/OCT 2023, the Amundsen Sea low has disappeared and been replaced by an upper ridge. The presence of the Amundsen Sea low (since 2016) and isolated disruption (2019 and 2023) seems to be independent of ENSO phase. The effect of this regime on Brazil rainfall for AUG/SEP/OCT is generally wetter than normal. However, during the past 3 months, Central Brazil is notably dry while rainfall has consolidated mostly in East/Southeast Brazil.

As a reminder, the long-term ENSO cycle shifted to La Nina in the late 1990’s and has remained in-place through 2022. An El Nino has formed in 2023 but is not anticipated as a sign of ending the long-term cold ENSO cycle. The long-term cold ENSO cycle has produced a drier climate change across Brazil leading to higher susceptibility of drought and flash drought plus lowering river levels.

Historically, global atmospheric angular momentum (GLAAM) has tendency to increase during El Nino due to increased vertical wind shear and upper-level wind increase in the subtropics of both hemispheres. The increased wind in the global subtropics increases GLAAM. However, despite El Nino presence in late 2023, GLAAM has shifted negative. Proposed is the unusual negative shift in GLAAM is due to the warming of the mid-latitude oceans of the past decade or so lowering or eliminating south-to-north subtropical oceanic thermal gradient, vertical wind shear, and wind aloft.   

A mild El Nino winter is ahead for most of the northern hemisphere. Cold air bursts can still happen, although one way to trigger arctic outbreaks (sudden stratospheric warming) is less likely to occur due to the expectation of increased solar wind in the upper atmosphere as related to increased solar activity.