![]() ![]() That said, it will linger even with a strong wind in locations where there is a large difference between the water and air temperatures.įrontal fog will quickly pass and radiation fog will burn off – a bit of patience really does go a long way. So, to get better visibility you will have to wait for a change in wind direction or speed – in most cases once the wind increases to over around 15 knots, fog lifts to low stratus clouds and visibility improves. The tide may introduce a change in the water temperature, but it’s not usually enough to clear fog. This may be feasible if you’re close to the Gulf Stream, but generally it is impossible. With advection fog you either need a change in the wind direction to shift the air mass to a drier, cooler source region, or you need to sail to warmer water. Knowing the different processes of the development of fog helps you to decide your tactics. As the air becomes saturated some of the vapour condenses into fog. This forms when rain falls into cooler, drier air and some of the drops evaporate into water vapour. The final main process that generates fog is known as frontal fog. The fog indicated cold water and bergs or ‘bergy bits’ (small ice that doesn’t show on radar, but is big enough to do damage) could be around spectacular sailing, but also somewhat on the scary side. We were pushing hard, so we all slept feet forward just in case.įog and ice are not great sailing companions and in the days of the Whitbread Round the World Race (see some great images of EF Education from the 1997-98 race here), before the use of ice gates in the Southern Ocean, poor visibility was a source of concern owing to the increased chance of ice. We found ourselves surrounded by radar echoes on one occasion and although most of these were fishing boats, some may have been ice. When considering a passage along the northern route from the US to Europe, staying north or south of the Gulf Stream will usually make all the difference in temperature and visibility. Cold water moving south with the Labrador Current provides a steep temperature gradient between the currents, causing thick fog banks to form quickly as the warm air moves over the colder waters. The prevailing wind direction is south-westerly, which brings warm moist air from the Tropics and the Gulf Stream. The best known fog in the Atlantic is that found over the Grand Banks. Sea fret doesn’t penetrate far inland, but it means the east coast can struggle with low temperatures and poor visibility while the rest of the UK basks in sunshine. ![]() By the time it reaches the UK dense fog has formed. In an east wind, warm continental air moves over the cooler North Sea. Indeed, it can be so common that the fog receives a local name – the Haar or sea fret along the east coast of England and Scotland, for example. Various locations are prone to fog with a given weather pattern. It was a fairly memorable race, but not for the right reasons. In one recent Round Britain Race, we started from Calais in fog and returned down the North Sea in even thicker fog it did lift a little for a while in between. This can take anything from hours to days. This happens over a large area and will persist until there is a change in the air mass. Fog is formed from the numerous water droplets. The cold sea cools the air above to below its dew-point, causing moisture in the air to condense. What is advection fog?Īdvection fog – the widespread fog that covers large sea areas – is caused when a warm moist air mass moves over a cold sea. It usually feels as if you are sailing around in circles.Īt some stage all of us will encounter fog and it will have been generated by one of three processes. Foghorns are hard to pinpoint and the rumble of large engines seem closer than they actually are. Radar and AIS help to make navigating in fog safer, but it is still an unnerving experience to sail in visibility of less than 1,000m. ![]()
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