What are the 4 basic cloud FORMS?
- Cirrus: threadlike/hairy/fine
- Cumulus: fluffy/towering
- Stratus: sheet or layer
- Nimbus: rain
What are the 3 cloud types in the high etage?
What altitude are the formed between?
What are they composed of?
- Cirrus (Ci): fine strands/hooks or clumps
- Cirrostratus (Cs): a sheet of fine wispy/thread like cloud
- Cirrocumulus (Cc): lumps of cirrus
Between 20,000 and 40,000FT
Composed of ice crystals and responsible for VIRGA
What are the 2 cloud types in the middle etage?
What altitude are the formed between?
- Altostratus (As): a sheet of cloud, may produce rain OR virga
- Altocumulus (Ac): heaped or lumpy cloud not generally associated with rain
8,500 to 20,000FT
What are the 5 cloud types in the low etage?
What altitude are the formed between?
- Cumulus (Cu): heaped or towering cloud, may produce SHOWERS of RAIN or SNOW
- Cumulonimbus (Cb): towering thunderstorm producing HEAVY SHOWERS of RAIN, HAIL or SNOW
- Stratus (St): a LOW sheet of cloud producing DRIZZLE
- Stratocumulus (Sc): a sheet of heaped or towering cloud. May produce DRIZZLE
- Nimbostratus (Ns): a sheet of heavy rain cloud. Produces CONTINUOUS RAIN or SNOW
500 to 5000FT
What are the 5 lifting mechanisms of cloud?
- Convection
- Turbulence
- Orographic uplift (Over mountains)
- Mountain waves (for lenticular cloud)
- Frontal uplift
What cloud types will form for unstable orographic uplift?
Cumular form
What cloud types will for for stable orographic uplift?
Stratiform - nimbo stratus with heavy rain
What conditions are required for orographic form mountain wave cloud?
- Wind blowing at right angles to the mountain range (at least 25KTS at top of range; and
- A stable layer of air (inversion) above the range
lenticular cloud forms on the top of the a waves while rotor cloud forms under waves in the rotor zone
What is FRONT?
The boundary between two air masses of different temperatures
Normally associated with LOW pressure systems
What weather is generally associated with a cold front due to the forced rise of warm air?
Unstable conditions which result in frontal thunderstorms
How is a cold front depicted on a synoptic chart?
Sharp triangular barbs pointing in direction of movement
What conditions indicate the passage of a cold front in the Southern Hemisphere?
- A fall in temperature
- Backing of the wind
- A rise in pressure
What weather is generally associated with a warm front as warm air rides up over the cooler air?
Generally it forms stratiform cloud with rain from nimbostratus
How is a warm front depicted on a synoptic chart?
Semi circular shapes pointing in the direction of travel
What cloud indicates the approach of a warm front?
High level followed by mid level and then extensive nimbostratus
What conditions indicate the passage of a WARM front in the Southern Hemisphere?
- A rise in temperature
- Backing of the wind
- Pressure decreasing
What is an occluded front?
What weather conditions are associated with one?
Where a cold front has caught a warm front, depicted as triangular barbs and semi circles.
The conditions are characterised by both warm and cold front weather: often extensive cloud and widespread rain
How is a quasi stationary depicted on a synoptic chart?
Triangular barbs and semicircles pointing in opposite directions
A cold front usual lies along a:
A. Ridge of high pressure
B. Trough of low pressure
C. N - S line through a low
D. NE - SE line through a low
B. Trough of low pressure
A cold air mass is characterised by:
A. Stable conditions, stratiform cloud
B. Unstable conditions, cumuloform cloud
C. Stable conditions, cumuloform cloud
D. Unstable conditions, stratiform cloud
B. Unstable conditions, cumuloform cloud
Warm air masses are characterised by:
A. Turbulence and good visibility
B. Showers and thunderstorms
C. Stable with hazy conditions
D. Good visibility and thunderstorms
C. Stable with hazy conditions
Following the passage of a warm front, the most likely weather scenario would be:
A. Nil significant weather
B. Heavy continuous rain
C. Scattered showers
D. Thunderstorms
A. Nil significant weather
Frontal thunderstorms would be triggered:
A. By the passage of a warm front
B. By the passage of a cold front
C. Along a well formed trough of low pressure
D. Along a well formed ridge of high pressure
B. By the passage of a cold front
A defined boundary between 2 air masses is called a:
A. Col
B. Front
C. Ridge
D. Trough
B. Front
