Wind and frost cause ice accretion on vessels
Ice accretion warnings are issued during the winter season. Ice may accrete from sea water splashes, freezing rain or fog. Ice accretion warnings are issued for moderate and rapid icing.
Yellow is used in to indicate ice accretion warning.
Weather conditions affect the accretion of ice on ship structures
the temperature of air and sea water
The air temperature must be at -2° C or under it to cause freezing splashes in salty sea water. The surface temperature of sea water must be under +5° C. The stronger the wind, the higher the waves, and the more easily splashes are formed. Very humid air makes the situation worse. Similarly, rain or fog accompanying humid air accelerates the accretion of ice.
If the ship is sailing before the wind, ice accretion is considerably slower than if the ship is travelling at high speed against the wind.
The ice accretion warnings are in the FMI's webpages. They are read in connection with the marine weather forecasts on YLE Radio Suomi and Radio Vega.