Warm core intensification of a Tasman Sea cyclone linked to Coral Sea sea-surface temperatures.

In early June 2016 a large rainband with an embedded subtropical cyclone, associated with a deep upper-level trough, brought extensive heavy rainfall along Australia’s east coast, from southern Queensland to Tasmania. In the lead-up to this event, sea-surface temperatures (SSTs) in the Coral and Tasman Seas were the warmest on record for the time of year. 
To investigate how the anomalously high SST, and its distribution, influenced the development of the cyclone, a high-resolution configuration of the Australian Community Climate and Earth System Simulator (ACCESS) over Australia, known as AUS2200, has been run under different SST scenarios. All simulations were run from 0000 UTC 3 June to 0000 UTC 8 June 2016, and use ERA5 data for the SST calculations.
A more intense subtropical cyclone develops off the New South Wales (NSW) coast in two simulations run with observed SST — one with fixed initial SST (Control) and the other with daily evolving SST (Evolving) — compared with a simulation using 3 June climatological SST (Climatology). The cyclone also stalls longer near the NSW coast in the observed SST runs.
Two additional simulations examine the role of the East Australian Current in the Tasman Sea. One smooths a prominent warm eddy (Smooth), and another replaces the Tasman Sea SST with climatological values (Tasclim). Both simulations retain the cyclone intensification seen in Control. A final simulation that replaces the Coral Sea SST with climatological values (Corclim) produces a weaker cyclone similar to Climatology.
Taken together, the results indicate that the anomalously warm Coral Sea SSTs were more important for the cyclone intensification than those of the Tasman Sea even though the greatest intensification occurred over the Tasman Sea. The greater cyclone intensity and slower southward movement over the Tasman Sea resulted in stronger and more prolonged onshore winds along the southern NSW coast, increasing the potential for coastal damage.
The greater intensity of the subtropical cyclone seen in Control, Evolving, Smooth, and Tasclim is associated with the formation of a warmer deep-tropospheric storm core than seen in Climatology and Corclim. This is linked to a greater reservoir of deep-tropospheric warm air that develops when using observed SST over the Coral Sea. These findings highlight the critical role of the Coral Sea’s warm SST as a driver of the cyclone’s development and intensification.