Extended Abstract (192K)16D.1
Model based diagnosis of the genesis phase of Atlantic Hurricane Karen
Michael J. Fries Jr., University of Wisconsin, Madison, WI; and J. E. Martin
Tropical cyclones in the Atlantic Ocean typically develop in association with westward moving middle and upper tropospheric tropical waves at subtropical latitudes and are characterized, in their mature stage, by a tropospheric-deep tower of potential vorticity occupying their warm cores. Hurricane Karen (October 2001) acquired this characteristic structure but initially developed as an extratropical cyclonic disturbance. In this paper we employ a high resolution, MM5 simulation to investigate the extratropical genesis phase and tropical conversion of Atlantic Hurricane Karen.
Karen developed as an extratropical disturbance on the cold side of a baroclinic zone associated with a midlatitude cyclone to its northeast. A burst of convection in its incipient stages of growth provided sufficient latent heating to establish a PV tower at the center. This heating attempted to drive the development of a warm core, but strong cold advection on the cold side of the baroclinic zone impeded this development until the system achieved seclusion from the large scale cold environment, a characteristic of subtropical cyclones. The subsequent interaction between the low-level circulation and the intrusion of high PV, high qe air from the upper troposphere quickly established a tropical cyclone structure to Karen. Details of this unusual tropical cyclone formation will be discussed in the light of diagnosis of the model output.
Session 16D, Tropical cyclone extratropical transition I
Friday, 7 May 2004, 8:00 AM-9:45 AM, Napoleon III Room
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