THE Far South Coast of NSW had largely escaped the current heatwave hitting the rest of the country with sea breezes keeping temperatures at or around 30 degrees.
There has however been on weather phenomenon that one would not expect in a heatwave – thick fog.
Calm conditions in the mornings have led to thick banks of fog coming in from the ocean, caused by the warm ocean, humid air and temperature inversions.
In Narooma on Thursday morning, the fog only lifted around 9am while the Marine Rescue unit at Eden also reported visibility down to 200 metres.
The fog on Wednesday morning was even more widespread shrouding farmland as far inland as Bodalla as well as Bega.
Andrew Thaler reported to us via Twitter that a similar fog descended down Brown Mountain into the Bega Valley around 7am.
There has been little relief from the heat in the early mornings with Far South Coast residents perhaps feeling it most overnight with temps hovering around the 20 degree mark.
According to the Bureau of Meteorology, advection fog develops when warm moist air moves (advects) over a cooler surface resulting in the cooling of the air to below its dewpoint temperature, and subsequent saturation and condensation.
A certain amount of turbulence is needed for proper development of advection fog, thus winds between 6–15 knots are commonly associated with advection fog.
Not only does the turbulence facilitate cooling through a thicker layer, but it also carries the fog to greater heights. Unlike radiation fogs, advection fogs are often thick and persistent.
Then there is sea fog - it develops when moist air that has been lying over a warm water surface moves over a colder water surface, resulting in the cooling of this air to below its dewpoint temperature.
They are relatively rare in the Australian region, but when they do occur they are often widespread and persistent even in moderate strength winds.
Sea fog has been known to persist for several days around the Australian coastline and can occur at any time of the year.
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