Simulations of low‐level convergence lines over north‐eastern Australia

Abstract

AbstractWe describe high‐resolution numerical model simulations of low‐level convergence lines over north‐eastern Australia using the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5). The simulations are for selected events that were documented during the Gulf Lines Experiment, held in September–October 2002. The calculations provide further insights into the dynamics of the convergence lines and the mechanisms involved in their formation. In particular they show two clearly distinct convergence lines, one that corresponds to the morning glory and one which corresponds to the North Australian Cloud Line; the former originates from the east‐coast sea breeze over Cape York Peninsula south of about 14°S, while the latter originates from the east‐coast sea breeze north of this latitude. They support also a recently proposed conceptual model for the generation of southerly morning glories and show for the first time the separation of a bore‐like disturbance following the collision of a nocturnal cold front to the south of the inland trough with a sea‐breeze front to the north of the trough. Moreover, they show the progressive transition of the east‐coast sea‐breeze front and the inland cold front from gravity‐current‐like flows to bore‐like disturbances overnight to form north‐easterly and southerly morning glories, respectively. Copyright © 2006 Royal Meteorological Society.