Regeneration of the Southerly Buster of Southeast Australia

Helen J. Reid School of Mathematics, University of New South Wales, Sydney, Australia

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Abstract

The southerly buster has been successfully simulated using a numerical weather prediction (NWP) model and verified (particularly the sea level pressure field). This simulation was then used to study the behavior of the southerly buster in the region of the Hunter Valley, New South Wales, Australia, with the reintensification of the surge. In simulating the dynamics of the southerly buster in the vicinity of the Hunter Valley, both the horizontal and vertical resolution of the NWP are important. This was found through a series of simulations of a case study of 27 February 1998. The best simulation was achieved with 20 vertical levels, a coarse nesting into the Australian Bureau of Meteorology Limited Area Prediction System model, then down to finer grids in progressively higher resolutions.

The pressure ridge associated with the southerly buster is induced by the southerly flow up the southern parts of the Great Dividing Range resulting in anticyclonic vorticity that creates a region of high pressure ahead of the main high pressure cell behind the frontal system. This same mechanism is used to explain the reintensification of the surge at the northern part of the Great Dividing Range, which is characterized by a renewed peak in wind speed north of the Hunter Valley.

Corresponding author address: Dr. Helen J. Reid, Bureau of Meteorology, Level 16, 300 Elizabeth St., 2000 Sydney, Australia.

Email: helen@maths.unsw.edu.au

Abstract

The southerly buster has been successfully simulated using a numerical weather prediction (NWP) model and verified (particularly the sea level pressure field). This simulation was then used to study the behavior of the southerly buster in the region of the Hunter Valley, New South Wales, Australia, with the reintensification of the surge. In simulating the dynamics of the southerly buster in the vicinity of the Hunter Valley, both the horizontal and vertical resolution of the NWP are important. This was found through a series of simulations of a case study of 27 February 1998. The best simulation was achieved with 20 vertical levels, a coarse nesting into the Australian Bureau of Meteorology Limited Area Prediction System model, then down to finer grids in progressively higher resolutions.

The pressure ridge associated with the southerly buster is induced by the southerly flow up the southern parts of the Great Dividing Range resulting in anticyclonic vorticity that creates a region of high pressure ahead of the main high pressure cell behind the frontal system. This same mechanism is used to explain the reintensification of the surge at the northern part of the Great Dividing Range, which is characterized by a renewed peak in wind speed north of the Hunter Valley.

Corresponding author address: Dr. Helen J. Reid, Bureau of Meteorology, Level 16, 300 Elizabeth St., 2000 Sydney, Australia.

Email: helen@maths.unsw.edu.au

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  • Reid, H. J., 2000: Modeling coastally trapped wind surges over southeastern Australia. Part II: Intensity and depth. Wea. Forecasting,15, 174–191.

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