While this comes from the other side of the planet and may or may not be applicable to the specific meteorology of the Australian east coast, in the USA the 18,000 winds are called the “steering winds” of storm systems. More specifically, meteorologists will look at the 500 millibar upper air chart (the winds following the 500 millibar constant pressure surface, which varies around an average of 18,000 feet-“ish”). This shows a good representation of the general vorticity (“spin”) in the atmosphere, since at that point roughly half the atmosphere is above and below.