A Hypothesis for the Redevelopment of Warm-Core Cyclones over Northern Australia

Tropical cyclones moving inland over northern Australia are occasionally observed to reintensify, even in the absence of well-defined extratropical systems. Unlike cases of classical extratropical rejuvenation, such reintensifying storms retain their warm-core structure, often redeveloping such feat...

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Bibliographic Details
Published in:Monthly weather review 2008-10, Vol.136 (10), p.3863-3872
Main Authors: EMANUEL, Kerry, CALLAGHAN, Jeff, OTTO, Peter
Format: Article
Language:English
Subjects:
Atmospheric models
Cyclones
Deep layer
Earth, ocean, space
Exact sciences and technology
External geophysics
Feasibility studies
Heat conductivity
Heat flux
Heat transfer
Hurricanes
Hypotheses
Meteorology
Moisture effects
Rain
Rainfall
Redevelopment
Sandy soils
Sea level
Simulation
Soil
Soil moisture
Storms
Thermal diffusivity
Time series
Tropical cyclones
Wind
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Summary:Tropical cyclones moving inland over northern Australia are occasionally observed to reintensify, even in the absence of well-defined extratropical systems. Unlike cases of classical extratropical rejuvenation, such reintensifying storms retain their warm-core structure, often redeveloping such features as eyes. It is here hypothesized that the intensification or reintensification of these systems, christened agukabams, is made possible by large vertical heat fluxes from a deep layer of very hot, sandy soil that has been wetted by the first rains of the approaching systems, significantly increasing its thermal diffusivity. To test this hypothesis, simulations are performed with a simple tropical cyclone model coupled to a one-dimensional soil model. These simulations suggest that warm-core cyclones can indeed intensify when the underlying soil is sufficiently warm and wet and are maintained by heat transfer from the soil. The simulations also suggest that when the storms are sufficiently isolated from their oceanic source of moisture, the rainfall they produce is insufficient to keep the soil wet enough to transfer significant quantities of heat, and the storms then decay rapidly.
ISSN:0027-0644
1520-0493
DOI:10.1175/2008MWR2409.1