Fig. 1: NCEP CFS V2 upper air forecast for November 2021 across South America.
Discussion: Operational models indicate an amplified upper trough pattern that could initiate record-cool temperatures in the 11-15-day period across west/central Australia lingering for much of the remainder of November once established (according to ECMWF). The upper trough will cause widespread wetter than normal weather from northwest-to-southeast across Australia in November. The November upper trough is no stranger to Australian climate during a La Nina regime. Using both Nino34 SSTA and multivariate ENSO index (MEI) for the past 10 months of November when La Nina was present renders the semi-permanent November upper air climatology for Australia featured in today’s operational models although the 2021 version looks more intense.
Fig. 2: Climatology of the upper air pattern across Australia during November when La Nina is present since the late 1990’s.