03/04/2020, 10:33 am EST
The January/February 2020 arctic oscillation (AO) averaged +2.9 (second strongest on record) with the February AO index (+3.417) the strongest on record (for February). Identified by the vigorous +AO regime is an intense polar vortex anchored near the North Pole and strengthening the thermal ribbon in the upper atmosphere between very cold upper air in the polar region and warmer regime in the subtropics.