Note: Single-source report; awaiting corroboration.
NASA’s Terra satellite captured a view of morning fog filling valleys in national parks across the Victorian Alps during autumn, when nights are cool enough for fog to form. Radiation fog develops when air temperature drops to the dew point, causing water vapor to condense into tiny droplets close to the ground. This process was enhanced as dense cold air settled in the valleys first. The fog lingers in mountain valleys, which remain shaded longer, while dissipating more quickly in low-elevation areas warmed by the Sun. On this occasion, geostationary satellite images showed the valley fog lasting about two hours. Water bodies such as the Mitta Mitta River, Buffalo River, Livingston Creek, Lake Dartmouth, and Snowy River likely contributed moisture to the fog by adding vapor to the region’s atmosphere.
At approximately 8:19 a.m. local time, the Terra satellite also recorded an arch-shaped cloud stretching across Port Phillip Bay, from St. Leonards on the western shore to Mount Eliza on the east. This cloud is thought to have resulted from the convergence of land and sea breezes interacting with the bay’s distinctive horseshoe-shaped terrain. Satellite data indicated the arch-shaped cloud moved southward over the bay as the northeastern valley fog began to dissipate.