Black frost

The question was raised because of the trawlers of the lost Hull trawlers Lorella and Roderigo, which, it has been suggested, were not adequately warned of the freak black frost conditions by shore-based radio stations.

Source: wiktionary

‘Black Frost is like a dense mist and when it lifts it leaves ice all over the ship the ropes round the masts are sometimes 1½ feet in diameter. When black frost hits a ship men are allowed to drink rum by the bottle to keep themselves warm.’

Source: wiktionary

The air temperature is most important and a sudden drop may well indicate imminent icing conditions. This drop is often made obvious by the formation of Arctic frost-smoke fog, or ‘black frost’ as it is known by fishermen. It occurs quite frequently in these waters when a sea-air temperature difference exceeds 10 degC and is regarded by fishermen with some apprehension, but there seems little justification for this unless the portent of icing conditions developing is the reason.

Source: wiktionary

[…] "black frost" may extend above the observer covering the whole ship. The reduction in horizontal visibility will depend on the height above the sea to which the phenomenon extends. Trawlers heavily iced due to black frost have been known to capsize in Arctic fishing grounds.

Source: wiktionary