Weather Flashcards
Define conditions to classify FOG
Visibility less than 1000m
What 2 processes create fog when air is cooled below its dew point?
Radiation - air close to the ground cooled by radiation. Strongest on clear night and inversion.
Light wind will deepen fog
Advection - warm air cooling as it flows over land (ie wind from sea)
What 2 things disperse fog?
Temperature rises above dew point or wind mixes in drier air causing evaporation
What 3 things must exist for a thunderstorm to develop?
- Unstable conditions (steep ELR)
- Abundant supply of water vapour (high humidity)
- A lifting mechanism (front/heat/terrain/convergence)
What are the 3 stages of thunderstorm development?
- Cumulus stage
- Mature stage
- Dissipating stage
Describe the CUMMULUS stage of thunderstorm development
How long does it typically last?
A cumulus cloud.
UPDRAFTS ONLY PRESENT AS CLOUD BUILDS.
Cloud warmer than environment so vertical developments continues.
10-15 mins
Describe the MATURE stage of thunderstorm development
How long does it typically last?
When precipitation falls from cloud base.
BOTH updrafts and DOWNDRAFTS.
- downdrafts are associates with frictional drag from precipitation; and
- chilling of unsaturated air by evaporation of rain and cloud droplets
Maximum amount of lightning activity.
Cloud is now a Cb
15-30 mins
Describe the DISSIPATING stage of thunderstorm development
How long does it typically last?
Updrafts cease leaving ONLY DOWNDRAFTS.
Rain decreases, cloud breaks up.
30 mins
At which latitude would there be greatest difference between the actual wind and the gradient wind at 5000ft AGL:
A. 15 degrees S
B. 5 degrees S
C. 35 degrees S
D. 25 degrees S
B. 5 degrees S
Surface friction causes:
A. Increased cross-isobar flow
B. A decrease in speed of a low jet stream
C. A decrease in Coriolis effect
D. A decrease in gradient wind
C. A decrease in Coriolis effect
Conditional stability is said to exist when:
A. Both saturated and dry air are unstable
B. Both saturated and dry air are stable
C. Saturated air is stable but dry air is unstable
D. Saturated air is unstable but dry air is stable
D. Saturated air is unstable but dry air is stable
Which conditions are most likely to produce radiation fog:
A. Broken cloud with no wind
B. Thin overcast cloud with no wind
C. Scattered cumulus with light winds
D. Nil cloud and light winds
D. Nil cloud and light winds
Where is hail most likely to be encountered inside a thunderstorm?
A. In the anvil
B. Just below the base
C. At freezing level
D. Between 10,000 and 30,000 ft
D. Between 10,000 and 30,000 ft
Which of the following cloud types is most likely to produce virga?
A. Nimbostratus
B. Thin stratus
C. Cirrostratus
D. Thin altostratus
D. Thin altostratus
Which is most likely to be encountered in nimbostratus cloud?
A. Lightning
B. Intermittent rain showers
C. Drizzle
D. Heavy continuous rain
D. Heavy continuous rain
