If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user

Freezing Fog

From SKYbrary Wiki
Article Information
Category: Weather Weather
Content source: SKYbrary About SKYbrary
Content control: Royal Meteorological Society (RMetS) Royal Meteorological Society (RMetS)
WX
Tag(s) Weather Phenomena
Icing

FZFG

Definition

Fog comprised of supercooled water droplets which normally deposit rime ice on contact with an object with a surface temperature of less than 0°C273.15 K
32 °F
491.67 °R
. Fog is generally defined in terms of visibility being less than 1000m horizontally and freezing fog typically forms in the temperature range of -0°C273.15 K
32 °F
491.67 °R
to -20°C253.15 K
-4 °F
455.67 °R
. Freezing fog is reported as FZFG on a METAR report.

Description

Surface contact with subzero surface temperatures notwithstanding, water droplets will continue to exist in supercooled liquid form until the temperature drops below -10°C263.15 K
14 °F
473.67 °R
to -20°C253.15 K
-4 °F
455.67 °R
at which time the droplets are likely to freeze and become ice crystals (see Ice Fog).

Effects

Freezing Fog will leave only a thin film of frost or rime ice on an aircraft, which nevertheless needs to be removed before flight with a de-icing treatment. Aircraft should also receive an anti-ice treatment before commencing a take off if freezing fog conditions exist for the taxi and take off phases of flight in order to prevent further build up of ice.

Related Articles