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Tropical Cyclone behaviour in the South Pacific

Adjunct Professor James P. Terry and Dr Gennady Gienko


Improving our understanding of the characteristics and behaviour of tropical cyclones is a priority in the South Pacific, first because developing island nations in the region are adversely affected by the environmental and economic impacts of severe storms, and second, evolving scenarios of climate change point towards the likelihood of more intense storms occurring in a greenhouse-enhanced warmer world.  Preliminary findings from GIS analysis of cyclone tracks across the South Pacific are presented here.  Track sinuosity patterns were investigated over the last four decades, which covers the modern era of satellite observations.  Observations suggest that cyclone track sinuosity is an important parameter influencing the potential vulnerability of Pacific Island archipelagoes to cyclone strike (and therefore damage).  This is because cyclones that follow complex, convoluted or looping tracks affect greater areas and are therefore more likely to impact larger numbers of islands than storms that follow relatively straight paths.  The maps below illustrate this by showing in colour the recorded cyclone tracks (1970 to present), within four different sinuosity categories (green - low/straight; blue - moderate/curved; red - high/sinuous; black - extreme/complex).  

Early analysis of the track data on which these maps are based indicates that 1. longer-lived cyclones tend to display higher sinuosities, 2. the most sinuous tracks are followed by cyclones occurring in more westerly parts of the South Pacific, and 3. average track sinuosity has increased over the period of record, which may reflect improving tracking technology but also points to the possibility of changing climatic influences on cyclone migration patterns.

This work forms part of a research project "Developing a Modern Accurate Tropical Cyclone Database for the South Pacific Region".  The umbrella project is generously funded by the Government of Taiwan RoC under their regional development assistance programme for the South Pacific 2007-8.


Map 1. Tropical cyclones with low sinuosities 1.0 - 1.09 (straight tracks)


Map 2. Tropical cyclones with moderate sinuosities 1.10 - 1.49 (curved tracks)



Map 3. Tropical cyclones with high sinuosities 1.5 - 1.99 (sinuous tracks)


Map 4. Tropical cyclones with extreme sinuosities 2.08 - 52.55 (complex tracks)


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