Meteorological winter 2020-21 (so far) is very warm across the U.S. despite presence of a moderate-to-strong negative arctic oscillation also projected to last through February. During 3 analog years when -AO was similarly intense the Central/East U.S. experienced historic cold. The explanation for the warmer winter across the U.S. is related in-part to a constricted polar ice cap and warmer mid-latitude ocean surface.

La Nina 2020-21 has entered the mature phase. All dynamic forecast models indicate La Nina will begin to weaken during quarter 1 of 2021 shifting to neutral phase during quarter 2 of 2021. Specific climate influences are likely due to this transition on the U.S., South America and Australia.

Thirty tropical storms in 2020 across the North Atlantic basin breaks the record of 28 set in 2005. The number of hurricanes (13) and intense hurricanes (6) was slightly below the 2005 record (15 and 7 respectively). Surprisingly, despite the number of events in 2020, the accumulated cyclone energy (ACE) index was 179.7 ranking 9th highest in the 1950-2020 climatology.

The northern hemisphere sea ice extent ranks 2nd lowest on record for the September 2020. The only year in which northern hemisphere sea ice was less abundant was 2012. The lack of sea ice does not mean that winter ahead will be warm.