Intensification rapide des cyclones tropicaux du sud-ouest de l'océan Indien : dynamique interne et influences externes

Abstract : Despite significant improvements in Tropical Cyclone (TC) track forecasts over the past few decades, anticipating the sudden intensity changes of TCs remains a major operational issue. The main purpose of this thesis is to analyze TC rapid intensification processes in relation with external forcing induced by upper-level troughs originating from the mid-latitudes. The impact of initial storm structure on storm evolution and prediction is also documented. An objective definition for rapid intensification in the southwest Indian Ocean is first proposed. The location and frequency of TC-trough interactions are identified, as well as TC-trough arrangements conducive to TC intensification. An interesting study case, TC Dora (2007), is chosen to run numerical simulations initialized with synthetic TC observations blended in a global analysis. The simulated TC-trough interaction is intricate with potential vorticity (PV) advection from the trough into the TC core at mid and upper levels. Vortex intensification first occurs inside the eyewall and results from PV superposition. Further intensification is associated with a subsequent secondary eyewall formation triggered by external forcing from the trough. The numerical model is able to reproduce the main features associated with outer eyewall spin-up, inner eyewall spin-down, and their effects on vortex intensity changes. Another numerical study examines typhoons in the northwest Pacific and demonstrates the critical role played by initial vortex structure in TC track and intensity prediction. Upgrading the initial specification of a TC inner-core structure in numerical models is recommended for future TC prediction improvements.
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Contributor : Marie-Dominique Leroux <>
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  • HAL Id : tel-00787099, version 2


Marie-Dominique Leroux. Intensification rapide des cyclones tropicaux du sud-ouest de l'océan Indien : dynamique interne et influences externes. Physique Atmosphérique et Océanique []. Université de la Réunion, 2012. Français. ⟨tel-00787099v2⟩



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