Potential Vorticity Streamers as Precursors to Tropical Cyclone Genesis in the Western Pacific
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Authors
Rozak, Edward J.
Subjects
Tropical Cyclones
Tropical Transition
Potential Vorticity
Tropical Transition
Potential Vorticity
Advisors
Moore, Richard
Date of Issue
2012-03
Date
Mar-12
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
The term tropical transition (TT) is used to describe the formation of a tropical cyclone from an extratropical precursor. The overarching goal of this thesis is to re-examine TT in the western North Pacific. This is accomplished via the synthesis of a subjective climatology of all tropical cyclones (TCs) from 20022008 and a case study analysis of ensemble prediction data for the particularly intriguing event of TS 16W in September of 2008. The climatological analysis indicated that TT events represented 14% of all TCs during the study period. The maximum frequency of TT events occurred in the late summer / early fall. The resulting storm systems tended to form farther to the north than non-TT events and were found to be relatively weak and short- lived. The results of the case study analysis lend credence to the earlier finding that the genesis pathway of TS 16W exhibited a two-stage evolution. The first stage involved the forcing of near-continuous deep convection by a tropopause-level potential vorticity (PV) anomaly. The second stage involved the rearrangement of the upper-level PV structure via diabatic processes, resulting in a necessary reduction of vertical wind shear.
Type
Thesis
Description
Series/Report No
Department
Meteorology