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Intensification and Structure Change of Super Typhoon Flo as Related to the Large-Scale Environment.

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Master's thesis,

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A Multi-Quadric MQ analysis is developed and compared with the four-dimensional data assimilation analyses of the structure of Typhoons Flo and Ed during the Tropical Cyclone Motion TCM-90 field experiment. The MQ analysis has been shown to provide an alternate, plausible depiction of the tropical atmosphere. These analyses are used to compare physical processes leading to rapid intensification of Flo, but not of Ed. Significant documentations include 1 the existence of a cyclonic wind burst extending beyond 1000 km radius at 200 mb during the forcing phase for Typhoon Flo, which appears to be the result of strong, sustained eddy flux convergence of angular momentum EFC in the upper troposphere 2 a complex EFC vertical structure that evolved with time 3 Flo had developed a warmer core near the tropopause, and was less stable than Ed in the upper troposphere prior to the beginning of the rapid intensification period 4 a high correlation of the mid-troposphere azimuthally-averaged absolute vorticity with the 48-h future intensity of four tropical cyclones and 5 the 850 - 200 mb vertical wind shear for Typhoon Ed was less than the vertical shear calculated for Typhoon Flo, which implies that low vertical shear, although necessary for significant storm development is not, by itself, a sufficient dynamic factor to ensure rapid intensification. A conceptual model is proposed for tropical cyclone rapid intensification and subsequent weakening that accounts for varying EFC and vertical shear values. Although based on Typhoon Ed and Flo, this model is also consistent with intensity changes of Typhoons Yancy and Zola.

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  • Meteorology

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