That one went to Sydney not back to Melb. No point going to NTL when SYD is right next door and is large VA base should they wish to reposition it. Brisbane was copping the same storm as was Sunshine Coast. Some diverted to Rocky.
My previous employer strongly discouraged diverting to non/company airports in sticky weather situations on occasions when we departed knowing the forecast wasn’t overly great (and hence carried a lot more fuel for a return to base) and preferred the aircraft returned to base, cancel the flight and they can funnel the pax around the network on other services to avoid destroying the rest of the schedule with an aircraft stuck somewhere.