26th Conference on Hurricanes and Tropical Meteorology


Paradigms of tropical cyclogenesis in the Western Pacific

John E. Molinari, University at Albany/SUNY, Albany, NY; and D. Vollaro, K. Lombardo, and C. Schreck

Two general conceptual views of tropical cyclogenesis exist for western Pacific Ocean storms. The first of these places emphasis on the location and strength of the monsoon trough, the magnitude of vertical wind shear, the existence of near-equatorial westerly surges and cross-equatorial surges (and their role in creating cyclonic background vorticity), and the occasional appearance of monsoon gyres. In this view, the MJO is rarely if ever mentioned, and the existence of waves or disturbances in the easterlies is viewed as irrelevant. Some claim that lower tropospheric waves in the easterlies do not exist in the western Pacific.

The alternative paradigm focuses on westward propagating disturbances, either equatorial modes or generic off-equatorial easterly waves, and their intensification in a zonally nonuniform environment. The latter can be caused by land-ocean contrast, the Madden-Julian Oscillation, or other slowly varying convective forcing. Tropical cyclogenesis is viewed as most likely within an intensifying synoptic-scale disturbance in a background flow favorable for wave growth. This group almost never acknowledges the existence or relevance of the monsoon trough, rarely mentions the role of vertical wind shear, and completely ignores surges and gyres.

In the talk we propose to assemble available evidence to evaluate these two paradigms, and to address whether it is possible to reconcile them, or whether one must be correct and the other incorrect.

extended abstract  Extended Abstract (108K)

wrf recording  Recorded presentation

Session 2C, Tropical Cyclogenesis II
Monday, 3 May 2004, 10:45 AM-12:14 PM, Napoleon II Room

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