A moist potential vorticity perspective on the presence of inertial instability along the subtropical jet during the extratropical transition process

Large-scale regions of negative potential vorticity (PV) are known to occur along the anti-cyclonic shear side of the northern-hemispheric subtropical jet. These events have been observed in association with tropical cyclones, often during the extratropical transition process. To better understand this phenomenon, a moist-PV framework is applied to a simple tropical cyclone conceptual model. In addition, the non-conservation of the full three-dimensional dry PV is considered in the eyewall region. It is reiterated that the frictionless PV tendency is given by the divergence of a flux oriented along vortex lines and scaled by the heating. Further partitioning of this flux into components along and across local isentropes yields further insights regarding extratropical/tropical interactions and the cononical PV structure of tropical cyclones.

Large-scale regions of negative potential vorticity (PV) are known to occur along the anti-cyclonic shear side of the northern-hemispheric subtropical jet. These events have been observed in association with tropical cyclones, often during the extratropical transition process. To better understand this phenomenon, a moist-PV framework is applied to a simple tropical cyclone conceptual model. In addition, the non-conservation of the full three-dimensional dry PV is considered in the eyewall region. It is reiterated that the frictionless PV tendency is given by the divergence of a flux oriented along vortex lines and scaled by the heating. Further partitioning of this flux into components along and across local isentropes yields further insights regarding extratropical/tropical interactions and the cononical PV structure of tropical cyclones.