As the days get shorter and the temperature begins to drop ahead of winter, fog becomes an increasing hazard for port operations and offshore rigs near Australia.

WHAT IS FOG?

Fog typically forms overnight when temperatures near the surface cool, causing the humidity of air increase. If the air temperature drops low enough, airborne water vapour will condense into tiny water droplets that are light enough to remain suspended in the air.

Fog can occur at any time of the year, although it is most prevalent during the winter months when the air near the surface is coldest.

Fog can form locally, or it can be dragged (or advected) into an area by the wind. In both cases, the fog can significantly reduce visibility.

In some parts of the world, fog can hang around for days. In London, there was a case of persistent fog that lingered for four straight days in December 1952.

Thankfully in Australia, fog usually clears a couple hours after sunrise, as sun warms the air and evaporates the water droplets.

SEA FOG

While most people have seen fog over land, fog can also occur at sea. This type of fog poses a risk to port and offshore operations near the Australian coastline.

Sea fog forms when warm and humid air moves over cooler water. As the warm air moves over cooler water, the air cools enough for its water vapour to condense into fog.

Interestingly, breaking waves release salt particles into the air that can aid in the formation of sea fog by helping initiate the condensation process.

Sea fog can also be advected over land and into ports with the right wind direction. For example, a northeasterly wind can drag sea fog over ports in NSW.

The reduced visibility in sea fog can halt operations on offshore rigs and restrict the use of helicopters. If cargo on cranes cannot be seen, logistics operations can also grind to a halt, reducing efficiency and productivity.

Weatherzone provides a range of fog forecasting and alerting tools to industries that operate in the ports and coastal waters around Australia. You can contact business@weatherzone.com.au for more information.