12.) MET - Met Phenonema

Question 1

Impact of cloud types:

STRATUS

Answer 1

Normally formed through the lifting of morning fog or when cold air moves at low altitudes over a region.

• May produce light drizzle
• Common cause of missed approaches due to low cloud base.

Question 2

IMPACT OF CLOUD TYPES:

CUMULUS

Answer 2

Considered a fair weather mid level cloud but with
atmospheric instability and strong vertical currents can quickly rise into TCu and CB’s

Question 3

IMPACT OF CLOUD TYPES:

NIMBOSTRATUS

Answer 3

Usually occurs along warm fronts leading to prolonged moderate to heavy rain or snow and a low cloud base.

Issues for the aerodrome controller include:
- heavy rain or snow over a long period of time,
- impaired braking action,
- aquaplaning,
- flooded runway,
- possible snow closure of aerodrome,
- poor horizontal and vertical visibility with a low cloud base

Question 4

IMPACT OF CLOUD TYPES:
TOWERING CU AND CUMULONIMBUS

Answer 4

INCLUDING THUNDERSTORMS, TURBULENCE AND ICING.

Impacts:
Weather clutter on ATM
Interference to comms and nav aids
Windshear
Crosswinds
Poor braking action
Lightning
Limited visibility
Diversions
Turbulence
Weather avoidance
Heavy rain or hail
Microburst

Question 5

Runway visual range (RVR))

Answer 5

Enables a more localised assessment of visual range in relation to a particular runway when the general met visibility is less than 1500 m.
Indicates the range over which the pilot of an aircraft on the runway centreline can expect to see the runway surface markings, the lights delineating the runway or identifying its centreline.

Question 6

RVR is reported in metres, rounded down to:

Answer 6

Nearest 25m for RVR below 400m
Nearest 50m for RVR between 400m and 800m
Nearest 100m for RVR above 800m

The minimum reportable RVR is 50m and the
maximum is 2000m.

Question 7

When do you commence human observation for RVR?

Answer 7

• Commence when official met. vis. less than 1500m.
• Continue until it is 1500m or more & RVR in excess of maximum that can be measured.
• Half-hourly intervals, or when significant changes occur.
• Light traffic: Before aircraft departs & 15 minutes before ETA of arrival.
• Significant changes to be passed until aircraft lands