Anomalous subtropical zonal winds drive decreases in southern Australian frontal rain

Abstract. Cold fronts make a significant contribution to cool season rainfall in the extratropics and subtropics. In many regions of Southern Hemisphere amount frontal has declined recent decades, but there been no change frequency. We show that for southeast Australia this contradiction cannot be explained by changes intensity or moisture at latitudes interest. Rather, declining is associated with weakening subtropical westerlies mid-troposphere, which part hemispheric pattern wind anomalies modify extratropical zonal wave 3. Fronts generate are strong penetrate well into subtropics, observed decrease southern can linked frequency 25∘ S.