The influence of atmospheric circulation patterns on cold air outbreaks in the eastern United States.

In this paper, we build upon previous literature in directly addressing the temporal relationship between the stratospheric and tropospheric polar vortex (PV), sea level pressure (SLP), and resultant cold air outbreaks (CAO). An atmospheric and teleconnection analysis was conducted on 49 predefined CAOs across the eastern United States from 1948 to 2016. Clusters of SLP, 100 and 10‐mb geopotential height anomalies were mapped utilizing self‐organizing maps (SOMs) to understand the surface, tropospheric PV, and stratospheric PV patterns preceding CAOs. The Arctic Oscillation (AO), North Atlantic Oscillation (NAO), and Pacific–North American (PNA) teleconnections were used as variables to explain the magnitude and location of mid‐latitude Arctic air displacement. Persistently negative SLP anomalies across the Arctic and North Atlantic were evident 1–2 weeks prior to the CAOs throughout the winter. The tropospheric and stratospheric PV were found to be persistently weak/weakening prior to mid‐winter CAOs and predominantly strong and off‐centred prior to early and late season CAOs. Negative phases of the AO and NAO were favoured prior to CAOs, while the PNA was found to be less applicable. This method of CAO and synoptic pattern characterization benefits from a continuous pattern representation and provides insight as to how specific teleconnections and atmospheric patterns lead to CAOs in the eastern United States. This study has shown that persistently negative SLP anomalies across the Arctic and North Atlantic were evident 1–2 weeks prior to cold air outbreaks (CAOs) in the eastern United States throughout the winter. The tropospheric and stratospheric polar vortex (PV) were found to be persistently weak/weakening prior to mid‐winter CAOs and predominantly strong and off‐centred prior to early and late season CAOs. [ABSTRACT FROM AUTHOR]