FROST IN NORTHEAST AUSTRALIA - TRENDS AND INFLUENCES OF PHASES OF THESOUTHERN OSCILLATION

A forecast method capable of estimating date of last frost and number of frosts per season in northeastern Australia some months in advance is described. Forecast ''skill'' is achieved using either Southern Osc illation index (SOI) patterns (phases) during the previous austral aut umn or a linear discriminant approach and the SOI. When applying these systems, it is possible to provide significantly different probabilit y distributions of day of last frost and number of frosts, depending o n the SOI patterns observed during the previous season. An analysis of the time series of frost frequency and date of last frost suggests an apparent warming trend in the data, resulting in a trend toward earli er dates of last frost and fewer numbers of frosts at many of the loca tions analyzed. The beneficial implications of the proposed frost fore casting system for enterprises such as winter agriculture in the regio n are believed to be significant.