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The development of tropical cyclones in the north‐west of Australia
Author(s) -
Foster I. J.,
Lyons T. J.
Publication year - 1988
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711448302
Subject(s) - cyclogenesis , climatology , african easterly jet , tropical cyclone , tropical cyclogenesis , tropical wave , subtropical ridge , storm , geology , ridge , trough (economics) , cyclone (programming language) , southern hemisphere , northern hemisphere , monsoon , extratropical cyclone , monsoon trough , geography , meteorology , oceanography , precipitation , paleontology , field programmable gate array , computer science , computer hardware , economics , macroeconomics
Abstract Case studies of developing and non‐developing tropical depressions in the north‐west Australian region during the 1979/80 and 1980/81 cyclone seasons have been constructed using conventional and satellite observations. These show that enhanced low‐level winds can occur during the lifetime of non‐developing disturbances and are not exclusively associated with cyclogenesis. Both types of system possessed lower‐level cyclonic circulations and there was an overlapping such that non‐developing storms could have stronger circulations than some developers. At upper levels, development was associated with the subtropical ridge being situated over the surface position of the disturbance. In contrast, the ridge tended to be located southwards of non‐developers. These findings are supported by calculations of area‐averaged vorticity at 850 and 200 mb. Cross‐sections of zonal winds show that non‐developing systems could exhibit weaker vertical wind shears than some developing storms. Developers had only moderate shears at worst and maintained a well organized lower cyclonic circulation. Such features are consistent with both classes of disturbance existing within the monsoon shearline. Non‐development was caused by interactions with large‐scale flows in the southern hemisphere that prevented the necessary conditions for cyclogenesis from being all fulfilled. This suggests a need for greater understanding of the influence of mid‐latitude events on depressions within the monsoon trough.