Impact of identification method on the inferred characteristics and variability of Australian East Coast Lows.

The Australian east coast low (ECL) is both a major cause of damaging severe weather and an important contributor to rainfall and dam inflow along the east coast, and is of interest to a wide range of groups including catchment managers and emergency services. For this reason, several studies in recent years have developed and interrogated databases of east coast lows using a variety of automated cyclone detection methods and identification criteria. This paper retunes each method so that all yield a similar event frequency within the ECL region, to enable a detailed intercomparison of the similarities, differences, and relative advantages of each method. All methods are shown to have substantial skill at identifying ECL events leading to major impacts or explosive development, but the choice of method significantly affects both the seasonal and in- terannual variation of detected ECL numbers. This must be taken into consideration in studies on trends or variability in ECLs, with a subcategorization of ECL events by synoptic situation of key importance.

Fig 6: Hit rates (within 1 day) for the four ECL identification methods (section 2) when detecting ECL events in the MLD, with bars indicating the 95% confidence interval from a using the bias-corrected accelerated bootstrap test (10 000 samples). Hit rates for sub- categories of ECL are also indicated, including easterly (E) and westerly (W) events; those in the cool (May–October) and warm (November–April) seasons; those associated with an east coast rainfall cluster, wind gusts >90 km/h, or significant wave heights >4 m; and explosive events.