Progress Test 6 Flashcards
(22 cards)
What are the two main types of cloud?
- Heaped clouds - associated with unstable atmosphere and caused by vertical lifting
- Layered clouds - associated by stable atmosphere, blanket of cloud
Clouds are classified by type which can be prefixed by their altitude. What are the three that can be used?
- Low level clouds from surface to 6500ft (name only)
- Medium level clouds from 6500ft to 23,000ft (Alto)
- High level clouds from 16,500ft to 45,000ft (Cirro)
What is the prefix for clouds with precipitation?
Will have the prefix nimbo (nimbus). Which means rain bearing.
What does stratus cloud mean?
Stratus refers to a flattened layer of cloud.
What is Low Stratus and It’s code?
Low stratus (ST)
-grey sheet
-the best can be very low
-visibility can be poor over large areas
-stable, little to no turbulence.
What is Nimbostratus and it’s code?
Nimbostratus (NS)
-thick dark grey
-Indistinct base
-Poor visibility over large areas
-stable with a lot of moisture
-associated with warm fronts
-brings prolonged heavy rain
What is Altostratus and it’s code?
Altostratus (AS)
-think white/light grey cloud
-clearly defined base
-little vertical extent
-little turbulence
What is Cirrostratus and it’s code?
Cirrostratus (CS)
-transparent veil high cloud
-produces halo effect
-signs of approaching wether front
What is Cumulus and it’s code?
Cumulus (CU)
-well defined
-usually detached but can be embedded in other clouds
-Varying heights but can have raid growth
-can be turbulent inside
-general visibility
-Likely atmospheric instability
What is Stratocumulus and it’s code?
Stratocumulus (SC)
-A hybrid cloud varying in forms
-large patches of widespread layer
-turbulence can increase with it’s vertical extent
What is Altocumulus and it’s code?
Altocumulus (AC)
-grey and white patchy cloud
-some precipitation possible
-white streaks are ‘Virga’ (rain or snow falling)
-can evaporate before reaching the surface
What is Cirrocumulus and it’s code?
Cirrocumulus (CC)
-not common
-regular flakes or ripples
-can be known as mackerel sky
What is Cumulonimbus and it’s code?
Cumulonimbus (CB)
-large vertical extent
-associated with thunderstorms
-severe turbulence, wind shear and severe icing
-Intense precipitation and lightning
-Should be avoided
What is Cirrus and it’s code?
Cirrus (CI)
-thin and wispy white cloud
-formed by ice crystals
-Little to no turbulence
-Move across the sky unchanging
In what two ways can the cloud base be estimated?
Ground temperature - dew point, using the difference and the lapse rate estimate how far from the surface the cloud will be, or:
(Temp-Dew point)x 400ft
Why might using the cloud base estimation with Dew point not be exact?
A small nucleus (e.g. dust partical) is required for condensation so cloud formation is not necessarily guaranteed.
What are the six cooling processes (cloud formation)
- Convection
- Orographic Lifting (air is forced upwards by terrain or obstructions)
- Convergence (where two air masses meet causing forceful lifting and cooling)
- Advection (where an air mass is cooled by moving over a clod surface)
- Mixing (air parcels at the surface of different temperatures cause turbulence and condense into clouds)
- Coastal Breezes (sea and land can cause localised cloud to form)
When forecasts report clouds what information does this contain?
Cloud type.
cloud base.
cloud topps.
extent of coverage
What does TCU stand for?
Towering Cumulus
When a forecast shows cloud base as 3400-4000 and cloud tops as greater than 10,00ft what will that look like?
034-040/xxx
What are clouds measured in?
Oktas, one Oktas equates to 1/8 of the sky.
What is the abbreviation for Few, scattered, broken and overcast clouds and what are their measurements in Oktas?
FEW = FEW = 1-2 Oktas
Scattered = SCT = 3-4 Oktas
Broken = BKN = 5-7 Oktas
Overcast = OVC = 8 Oktas
