Variable weather patterns, and therefore rainfall, can be a feature with a decaying La Nina event, and this has been the case in the past month. While centres such as Tamworth with 216 millimetres had its wettest March in more than 120 years and Gunnedah with 218mm its wettest March for 80 years, not that far away Dubbo had just 21mm or just 30 per cent of its average.
Variability was assisted by thunderstorms and as conditions favourable for thunderstorms decrease during the rest of autumn, such variability will reduce in the coming months.
Variability in the long-term climate indicators recently has also been significant. The Pacific Ocean has undergone quite a change since January, with patterns almost transitioning from full La Nina to developing El Nino in the space of a few months.
Temperatures through the central to eastern Pacific Ocean in some areas have warmed 4-6 degrees in the past month alone, which is a remarkable turnaround from three consecutive summers of La Nina domination, and almost all major climate models move the Pacific Ocean into a full blown El Nino pattern from the start of winter. This is then likely to persist for much of winter and spring at least.
As always, there is often a lag between the atmosphere and the ocean so this does not necessarily mean an immediate transition to dry conditions, but the mid to long range outlooks will likely be drier ones.
This scenario is supported by the Indian Ocean patterns. The Indian Ocean Dipole is in a neutral state but most models indicate it will trend positive towards winter. A positive IOD normally brings fewer northwest cloud bands over winter and early spring, and the combination of both an El Nino and possibly a positive (even if neutral to positive) IOD would both combine to result in a drier than average outlook.
Going against these trends is the unexpected fact that sea surface temperatures in the Coral Sea and Tasman Sea remain warmer than normal - very unusual given the warming in the eastern Pacific.
Although a fairly dominant westerly pattern may emerge for large parts of south-eastern Australia during the winter and spring months, even occasional bursts of easterly winds could pick up more moisture than normal from these warmer SSTs resulting in occasional but fairly significant rain events along the east coast.
Other consequences of more dominant westerlies in winter and spring are cooler than normal weather in winter with potential for a reasonable snow season in the Snowy Mountains and above average temperatures developing during spring with increasing fire risks.
