Mesoscale Evolution of a Continental Occluded Cyclone

Abstract

A diagnostic study of a continental occluding extratropical cyclone (ETC) during 1?2 November 1992 is presented using initializations from the Mesoscale Atmospheric Prediction System (MAPS), a hybrid sigma?isentropic coordinate model. Whereas recent studies have concentrated on maritime ETCs and have used numerical model simulations, this study employs diagnostic, observational data and model initializations to develop an occlusion model. In addition, isentropic parcel trajectories from a diabatic trajectory model are examined to trace the origin and termination of air parcels associated with the development of the occluded front. The chosen storm was a moderately deepening (i.e., typical) ETC over a data-rich continental region. This storm developed over the central United States, where commercial aircraft and a network of wind profilers provided copious asynoptic data aloft, which was ingested by the MAPS. Analyses of this well-defined occluded cyclone tend to verify that the advancing cold front overtakes the retreating warm front, though it does not ?ride up? the warm front, and that warm-sector parcels are lifted upward in the vicinity of the occluded front, thereby confirming that some of the parcels aloft over the surface occluded front do originate near the surface prior to occlusion. Discussion is also provided on the nature of the occluded front as a true frontal boundary.