I believe it’s currently fog. Although Sydney takes a big hit of weather diversions as 2 of the runways go out of action above a certain amount of wind. Which being directly next to the Pacific Ocean you can believe happens not infrequently
Diversions into CBR due sea fog in SYD along with a ground stop Airservices imposed on all SYD bound flights due WX. All flights were then provided slot times into SYD and allowed to depart.