Extreme Weather Events Originating from Tropopause Polar Vortex Interactions with the North Atlantic Jet Stream

Coherent vortices in the vicinity of the tropopause, referred to as tropopause polar vortices (TPVs) and also known as coherent tropopause disturbances, may be extracted from the Arctic in conjunction with high-latitude upper-level ridge amplification events. Once extracted from the Arctic, TPVs may subsequently interact with and strengthen midlatitude jet streams, and may act as precursor disturbances for intense midlatitude cyclogenesis events. The purpose of this study is to investigate extreme weather events (EWEs) that result from TPV interactions with the North Atlantic jet stream (NAJ) and associated waveguide. Preliminary case study investigations have shown that TPVs that interact with the NAJ may lead to the intensification and reconfiguration of the NAJ/waveguide, downstream baroclinic development, Rossby wave breaking, and EWEs between eastern North America and Europe. These investigations have also shown that TPV–NAJ interaction events exhibit considerable variability in their structure and evolution. This variability depends upon the large-scale flow configuration and whether TPVs interact with disturbances equatorward of the NAJ/waveguide, such as recurving and transitioning tropical cyclones.

Multiscale investigations of TPV–NAJ interaction events will be conducted utilizing high-resolution global gridded reanalysis datasets to address the aforementioned variability in order to better understand: 1) how TPVs are extracted from the Arctic, 2) how TPVs impact the NAJ/waveguide through the depth of the troposphere, 3) what role the preexisting configuration of the large-scale flow plays in the evolution of TPV–NAJ interaction events when the NAJ is perturbed by disturbances on its equatorward side, and 4) what circumstances enable TPV–NAJ interaction events to culminate in the development of EWEs. It is hypothesized that certain large-scale flow configurations will be more conducive to stronger TPV–NAJ interaction events than weaker TPV–NAJ interaction events. Such stronger TPV–NAJ interaction events are hypothesized to lead to greater downstream impacts than weaker TPV–NAJ interaction events. It is also hypothesized that the structure and evolution of TPV–NAJ interaction events will exhibit considerable variability depending upon how TPVs interact with midlatitude disturbances embedded within the NAJ and/or tropical disturbances equatorward of the NAJ. The variability in the structure and evolution of these aforementioned TPV–NAJ interaction events will be illustrated by means of case studies and composite analyses.