5.04 Clouds and Fog

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References: -Air Command Weather Manual Ch 8 -FTGU pages 124-126, 147 : References: -Air Command Weather Manual Ch 8 -FTGU pages 124-126, 147 40 Minutes 5.04 Clouds and Fog BC Online Ground School: Meteorology

Slide 3 : MTPs: Cloud Classification Types and Recognition Associated Precipitation Fog Formation and Types

Slide 4 : Clouds are classified by: and Shape Type/Way They Form Height Families

Slide 5 : Two Cloud TYPES: Stratus Cumulus

Slide 6 : Four Cloud FAMILIES: High (Cirro) bases between 16 500 and 45 000 feet Ice crystals Middle (Alto) Bases between 6500 and 23 000 feet Ice crystals, water droplets - Low (Strato) Bases from surface to 6500 feet - Clouds of Vertical Development May form as low as 1500 feet Water droplets above freezing

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Slide 8 : High Clouds 1. Cirrus (Ci) very thin wispy cloud, like it was made with an artist’s brush sometimes referred to as cats’ whiskers or mares’ tail generally no particular significance to flying

Slide 9 : High Clouds 2. Cirrocumulus (Cc) thin cotton like clouds looks like pattern of the sand at a beach no indication of future weather conditions

Slide 10 : High Clouds 3. Cirrostratus (Cs) thin high sheet of cloud sun or moon is visible, producing a halo effect often indicate an approaching warm front or occlusion and therefore of deteriorating weather conditions

Slide 11 : Mid level clouds 1. Altocumulus (Ac) layers of rounded masses of cloud that may lie in groups or lines sometimes associated with an approaching front but usually they have little value as a weather predictor

Slide 12 : Mid level clouds 2. Altocumulus Castellanus (Acc) altocumulus with turreted edges may develop into cumulonimbus a variation of AC with greater vertical extent characteristics include: instability, turbulence and shower activity

Slide 13 : Mid level clouds 3. Altostratus (As) thick veil of grey cloud that generally covers the entire sky occurs from lowering of base of CS at first, the sun or moon may be seen through the cloud, but they disappear as the cloud gets thicker indicates the near approach of a warm front some light rain or snow may fall from thick altostratus icing may occur

Slide 14 : Low Clouds 1. Status (St) uniform layer of low cloud resembling fog but is not touching the ground low visibility, drizzle and fog often associated

Slide 15 : Low Clouds 2. Stratocumulus (Sc) layer or series of rounded masses or rolls of cloud common in high pressure areas in winter sometimes gives a little precipitation

Slide 16 : Low clouds 3. Nimbostratus (Ns) ‘Nimbo’ – means precipitation is associated with the cloud low dark grey layer thickened altostratus associated with warm fronts and continuous/steady rain or snow may be more than 15,000 ft thick VFR operations often difficult to impossible

Slide 17 : Clouds of vertical development 1. Cumulus (Cu) Dense, thick, rounded and lumpy resembles cotton balls flat bases and sharp clear cut surfaces forming during day and dissipate at night height of base depends on temperature and dew point spread light to moderate turbulence NO PRECIPITATION

Slide 18 : Clouds of Vertical Development 2. Towering Cumulus (TCu) a development of cumulus cloud serious (moderate to heavy) icing and turbulence rain showers and snow showers in winter rough air underneath

Slide 19 : Clouds of Vertical Development 3. Cumulonimbus (Cb) development of TCU often anvil shape top produces lightning and thunder gusty surface winds in vicinity hail is often present within the cloud and may occasionally fall from it heavy icing, turbulence and showers may be embedded in stratiform clouds cloud should be avoided

Slide 20 : Name these clouds: 1 2 4 3

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Slide 22 : Fog is: Cloud (usually stratus) in contact with ground Formed when: Air cooled to due point Air becomes saturated (moisture added)

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Slide 24 : 1. Radiation Fog (ground fog) Forms at night Initial heating from sun causes turbulence Ground cools losing heat through radiation Air in direct contact is cooled Clear skies, moist air, light winds (2-5 knots)

Slide 25 : 2. Advection Fog When warm moist air moves over a colder land or sea surface Winds >15 knots Most frequent in costal regions Widespread when moist air from warm region of ocean moves over colder water

Slide 26 : 3. Upslope Fog Cooling of air due to expansion as it move sup slope Light upslope wind required

Slide 27 : 4. Steam Fog Cold air passes over warm water surface Evaporation of water into air until saturated Occurs over rivers and lakes, especially during autumn

Slide 28 : 5. Precipitation Induced Fog (frontal fog) Addition of moisture to air through evaporation of rain or drizzle The precipitation from warm air evaporates and saturates cooler air below Associated mostly with warm fronts

Slide 29 : 6. Ice Fog Moist air during extremely cold calm conditions The cold air cannot hold more moisture and excess sublimates into ice crystals Crystals appear suddenly when engine started Water vapour Condensation nuclei Mixing agent

Slide 30 : Watch the link: http://www.youtube.com/watch?v=KG0i-AsaGO4 What clouds can you name?

Slide 31 : What are the names for the 3 levels of clouds? Name one type of vertical development cloud. What requirements are needed to create fog? What type of precipitation would you get in: i) stratus clouds Ii) cumulus clouds