Lee cyclogenesis in New Zealand - A prediction scheme
A scheme for the prediction of lee cyclogenesis over the South Island of New Zealand is presented. The phenomenon of lee cyclogenesis becomes important when deep depressions impact on the Southern Alps. Under certain upper level conditions, deepening, (or accelerated deepening), occurs as the low redevelops to the east of the South Island, and there is a northward deflection of the track. A period of very strong winds can occasionally be produced. It was found that the occurrence of a 500 hPa jet at right angles to the Alps was a sufficient condition for the phenomenon to occur. An examination of a number of cases when lee cyclogenesis was occurring produced a relationship between the mean sea level pressures at various points before and after the traverse.