Confirming Chagnon and Gray, it is found that horizontal PV dipoles are related to vortex tilting, where horizontally-oriented vorticity associated with vertical shear of the ambient wind is bent into a horseshoe shape by the updraft, yielding a PV dipole. This suggests that theta dipoles are perpendicular to PV dipoles and that “low PV lies to the left of the wind shear”, or in the case of tropical cyclones, “low PV lies radially outward”. Mesoscale jets occur between the dipoles, which oppose the ambient anticyclonic flow, creating a new kind of steady-state configuration.
During the extratropical transition of Talas, convective PV anomalies evolved under synoptic-scale anticyclonic deformation into a pair of PV streamers, which modified the midlatitude westerly jet. The formation of a pair of PV streamers during the Super Tuesday storm in cyclonic deformation also formed a pair of PV streamers which accentuated the jet.
In a slight departure from Chagnon and Gray, who studied PV production within individual convective towers, it is suggested that the diabatic processes which are responsible for the synoptic-scale ambient vertical wind shear allow for vertical tilting by local updrafts, which impinge upon the base of the stratosphere, creating large PV dipoles.