4. Forecast Applications

Icing » Icing Forecasting Icing Type

Photos showing clear and rime icing on aircraft wings

Empirical studies have shown the type of icing depends on the ambient temperature as well as the types of clouds (vertical motions) in the environment.

  • Rime Icing occurs at temperatures colder than -15°C but can also occur at warmer temperatures in stratiform clouds.
  • Clear Icing occurs at temperatures between 0 and -8°C, in cumulus clouds, and/or freezing precipitation.
  • Mixed Icing (rime and clear) occurs in cumulus clouds at temperatures of -9 to -15°C.

Therefore, to evaluate the potential for icing from a skew-T plot, forecasters need to determine the thickness of the cloud/moist layer and the potential for supercooled conditions by examining the temperature, dewpoint depression, and lapse rate within the sounding.