Top view of WRF-ARW potential vorticity (PV) on the 322-K isentropic surface. Key features include: encirclement of the Sandy inner-core diabatic PV tower by polar stratospheric potential vorticity after 12:00 UTC 29 October 2012; enhancement of extratropical cyclonic wave breaking by Sandy's anticyclonic outflow jet in its northwestern quadrant. Color indicates potential vorticity units (PVU). Discussed in Mel Shapiro's presentation at the AMS 2013 Townhall "A research-community perspective of the life cycle of Hurricane Sandy"
