POTENTIAL VORTICITY DIAGNOSTICS OF HURRICANE MOVEMENT .2. TROPICAL-STORM-ANA (1991) AND HURRICANE-ANDREW (1992)

The validity of balance dynamics in the Tropics allows an exploration of the dynamics of hurricanes using the potential vorticity (PV) frame work. Part I demonstrated the use of PV diagnostics in understanding t he hurricane steering flow and also the interaction between the cyclon e and its environment. To obtain a broader understanding of this PV me thodology, two other observational case studies are performed (Tropica l Storm Ana of 1991 and Hurricane Andrew of 1992) emphasizing the same methods of analysis. The results are consistent with a previous findi ng that the hurricane advection flow, defined by inverting the entire PV distribution excluding the storm's own positive anomaly, is a good approximation to real cyclone movement even though the original data c annot capture the actual hurricane strength. This study confirms that upper-level PV anomalies can play an important role in the motion of t he storm. But their quantitative effect on the cyclone's motion depend s strongly on the relative location of the vortex and the upper-air PV features. Due to the limitations of the data, the beta effect or the mechanism proposed by Wu and Emanuel was not able to be supported or d isproved.