So how did La Nina precipitation climatology (from the past 25 years) for November compare with actual precipitation in the U.S., Australia and South America?

Now that tropical cyclone season is winding down we enter the next persistent issue for meteorological winter 2020-21 which is La Nina storms. La Nina storms produce three types of high impact weather certainly evident in the SUN/MON forecast.

A La Nina climate is normally wetter than normal across northern and eastern Australia. However, November has been dry in these sectors. Contributing to the dryness is the subsidence phase of the Madden Julian oscillation at the tropical longitudes of Australia.

Forecast models have over-forecast rainfall across the dry-to-drought portion of Brazil consistently the past 30 days for both short-range and medium-range timescales. Forecast models have a tendency to turn northwestern South America wet with a fetch of that moisture across Brazil (at times). Instead the northwest South America dry pattern (and drought) persists and central/south Brazil rains are failing.

Last week the Nino SSTA regions warmed significantly and La Nina lost intensity. In the eastern equatorial subsurface robust cool water supply diminished indicating fuel to sustain La Nina is less plentiful.

La Nina 2020-21 appears projected to be almost as strong as the 2007-08 episode ranking the event 3rd strongest of this century so far. The Climate Impact Company analog projection is based on 3 cold ENSO events from the past 25 years and the consensus projects peak intensity in January, weakening La Nina next spring, neutral ENSO next summer and possible return to weak La Nina DEC/JAN/FEB 2021-22.

Leading drought areas across the globe as of November 1 is the Western U.S. which inspired a record-setting fire season, one of the driest/drought periods on record for Paraguay and a harsh drought across Southwest Russia and the Black Sea region.

In October 2020 the Rutgers University Snow Laboratory snow cover analysis reveals 10.26 million square kilometers across North America which is (by far) the highest amount for the month observed in the 1970-2020 climatology.

-PNA patterns represent a persistent cold upper trough over Southwest Canada and/or the Western U.S. Frequently, -PNA patterns are compensated for by an upper ridge across the East U.S. associated with positive North Atlantic oscillation (+NAO). The described pattern is fully developed in the 6-10 day period and likely to linger through the 11-15 day timeframe.