We use satellite observations of cloud fraction over Australia from the International Satellite Cloud Climatology Project, and a new Northwest Cloudband (NWCB) identification algorithm to extend the record to cover the period 1984 to 2012. From this record, we have created a more robust climatology. Moreover, we propose conceptual models for summer and winter NWCBs after analysing the synoptic conditions associated with NWCBs in the two seasons using reanalysis data from ERA-Interim. We assess the viability of using statistical modelling to predict NWCBs based on typical synoptic conditions, and lastly, analyse the relationship between NWCBs and rainfall including how the probability of extreme rainfall changes during a NWCB day and how cold fronts interact with NWCBs to modulate rainfall based on the Australian Water Availability Product high-quality gridded rainfall dataset.

We conclude that the frequency of NWCB days has increased from 1984 to 2012, and this increase is apparent in all seasons except winter. We show that winter cloudbands are associated with baroclinic instability over northwest Australia, and summer cloudbands are often triggered by a low pressure anomaly such as a tropical cyclone, monsoon depression or heat low. The key difference between summer and winter NWCBs is their initiation mechanisms. Furthermore, we found NWCBs may enhance the probability of extreme rainfall by up to 12 times over northwest Australia, but reduce the probability of rainfall extremes in northeast Australia.