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Surface Cyclones over Austral Latitudes: Part II Cases Study

Abstract

This work presents the synoptic analysis of four types of cyclones in southern latitudes: extratropical type Bjerknes and Solberg, extratropical type Shapiro and Keyser, tropical and subtropical. Therefore, the main purpose of this study is to highlight, with synoptic analysis of some cases, the differences between these systems and complement the article “Surface Cyclones over Austral Latitudes: Part I Bibliographic Review”, in which a review of the literature about cyclones type was held. We analyzed two extratropical cyclones occurred in the Southwest South Atlantic Ocean; the subtropical cyclone called Arani, occurred in the same ocean basin and a tropical cyclone, which had genesis in the northeast of Australia over the Pacific Ocean and called Ului. The cyclones features were emphasized in four stages: pre-cyclogenesis, cyclogenesis, maturity (occlusion) and decay. Moreover, the lifecycle of the cyclones was investigated through a phase diagram (Cyclone Phase Space), which identifies the type of cyclone with only the information of the thermal structure of the atmosphere. Among the results, it is shown that the genesis of the extratropical cyclones was associated with horizontal temperature gradients in surface and a trough at 300 hPa; the subtropical cyclone had a dynamic support of a short wave trough at 500 hPa, which was important for the occurrence of upward movements in the atmosphere; and that the tropical cyclone was associated with a region of low cyclonic relative vorticity in low levels and surface mass convergence.

Keywords:
case study; extratropical cyclones; subtropical cyclones; tropical cyclones; life cycle; Southern Hemisphere

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