Aerodrome Forecasts and Observations Flashcards
Sources of MET Observations
Local Surface Observations
- Staffed stations
- Approved Observers
- Automatic electronic devices
- Oceanic buoys
Atmospheric observations
- Balloons
- Radiosondes
Airborne Reports
- By pilots (manual or automatic)
- ATC observations
OKTA Scale
NCD Nil Cloud
FEW 1-2 OKTAS
SCT 3-4 OKTAS
BKN 5-7 OKTAS
OVC 8 OKTAS
When is Embedded used to describe cloud?
When cloud is within another layer and is not readily recognised.
When is Obscured used to describe cloud?
When cloud is obscured by haze or smoke and cannot be readily seen.
What is Squall Line used to describe?
Thunderstorms along a line with little or no space between individual clouds.
SIGMET information concerns the occurrence, or expected occurrence, of one or more of the following:
- Thunderstorms
- Tropical cyclones
- Hail
- Severe turbulence
- Severe icing
- Severe mountain waves
- Widespread sandstorms or dust storms
- Volcanic ash cloud
SIGMETs for Thunderstorms are only issued when?
When the thunderstorms are:
- Obscured (OBSC) by haze or smoke and cannot be readily seen;
- Embedded (EMBD) within cloud layers and cannot be readily recognised;
- Frequent (FRQ) with little or no separation between adjacent storms and covering more than 75% of the area affected; or
- Squall line (SQL) thunderstorms, i.e. thunderstorms along a line with little or no space between individual clouds.
SIGMET format?
- WMO Bulletin Identifier
- WMO Indicator of originating office
- Date/Time
- YMMM or YBBB
- SIGMET standard identifier
- Daily Sequence Number
- Valid perior
- ICAO location indicator
- FIR Indicator
- Message description of phenomena
- STS meaning Status of SIGMET, followed by:
—– NEW meaning a New SIGMET,
—– REV meaning a Reviewed SIGMET, or
—– CNL meaning Cancellation of SIGMET.
Elements of AIRMET
AIRMET information concerns the occurrence or expected occurrence, in an area over which meteorological watch is being maintained, below level A100 of one or more of the following phenomena when the phenomena have not been included in a current Area Forecast:
- isolated and occasional thunderstorms
- Moderate icing
- Moderate mountain waves;
- Widespread areas of visibility < 8KM;
- Widespread areas of cloud coverage of BKN or OVC below 1,500FT AGL
CB or TCU clouds which are isolated, occasional or frequent.
What is a TAF?
- A forecast for an area 5nm from the Aerodrome Reference Point
- It is a statement of expected conditions for a specified time.
Elements of a TAF3?
Issued routinely every 3 hours at major airports
Adelaide, Brisbane, Cairns, Darwin, Gold Coast, Hobart, Melbourne and Sydney
Also provided at Military aerodromes as per ERSA. Any deviations from ERSA published TAF3 hours notified by NOTAM
Same format as TAF with “TAF3” in RMK section
Issued from the Aviation Forecast Office 30-60 minutes before the forecast validity period, with a target issue of 45 minutes
Replaces TTF (Trend Type Forecast)
Meaning of FROM (FM)?
- Indicates a rapid change from the preceding forecast of a lasting nature
- Can be an improvement or a deterioration
- The conditions following a FM period stay in force until another FM, BECMG, TILL or the end of the TAF/TAF3
- In a TAF the format is ddhhmm
- In a TAF3 the format is ddhh
Meaning of BECOMING (BECMG)
- Indicates a less rapid change from the preceding forecast of a lasting nature
- The change can be an improvement or deterioration
- Format is ddhh
- The conditions following a BECMG period stay in force until another FM or BECMG or the end of the TAF/TAF3
Meaning of PROBABILITY (PROB)
- Indicates a probability of a phenomena occurring
- PROB30 or PROB40 are the only ones used
- Less than 30% it is ignored
More than 40% it becomes a part of the forecast
Meaning of INTERMITTENT (INTER)
- Is used to indicate changes that will occur frequently for periods of less than 30 mins
- In a TAF the format is ddhh/ddhh
- In a TAF3 the format is ddhh/ddhh
Meaning of TEMPORARY (TEMPO)
- Is used to indicate change in prevailing conditions expected to last for periods of between 30 and 60 minutes in each instance
- In a TAF the format is ddhh/ddhh
- In a TAF3 the format is ddhh/ddhh
Meaning of CAVOK
- CLOUD AND VISIBILITY and weather OK
- Visibility of 10km or more
- No cloud below 5000ft or below the highest 25nm minimum sector altitude, whichever is greater
- No cumulonimbus or towering cumulus at any height
A TAF will include up to ____ temperature and QNH values from the commencement of the TAF, beginning at the start of the prescribed period and thence every ___________
- Four
- Three hours
METAR occur at what frequency?
Hourly or half hourly.
How can you determine if a METAR is automated?
Will contain the word AUTO
What are SPECI?
Aerodrome weather reports issued whenever weather conditions fluctuate about or are below specified criteria.
Runway Visual Range is calculated through the use of instruments called __________ which measure distance based on ______________
- Transmissometers 2. Moisture in the air.
Runway Visibility is __________ measured by calculating the number of _____________ visible from a prescribed location and calculating the distance based on ___________
- Visually
- Runway lights
- Spacing
RVR will not exceed what?
2000m
In what format may rainfall appear in a METAR or SPECI?
RF##.#/###.#
- The first three digits indicate rainfall in the 10 minutes prior to the observation.
- The next four digits indicate total rainfall since 9am local time
Rainfall is reported in __________ increments
0.2mm
Why are aerodrome warnings issued?
To provide concise information on meteorological conditions that could adversely affect the aerodrome’s facilities and services, and aircraft on the ground.
Warnings relate to the expected occurrence of the following phenomena:
- Tropical Cyclone
- Gale-force wind
- Squall
- Thunderstorm
- Dust-storm
- Sand-storm
- Rising sand or dust
- Hail
- Frost
- Rime ice
- Snow
- Freezing precipitation
- Volcanic Ash
- Tsunami
Criteria to trigger a SPECI
Wind Direction
- Changes of 30° or more, the mean speed before or after the change being 20KT or more
Wind Speed
- Changes of 10KT or more, the mean speed before or after the change being 30KT or more
Wind Gust
- Gusts of 10KT or more above a mean speed of 15KT or more
- Gust exceeds the last reported gust by 10KT or more
Visibility
- When the prevailing visibility is below the aerodrome’s highest
alternate minimum visibility or 5000M, whichever is greater*
Weather - When any of the following begins, ends, changes in intensity, or is
occurring at a routine reporting time:
- thunderstorm
- hailstorm
- mixed snow and rain
- freezing precipitation
- drifting snow
- squall
- fog (including shallow fog, fog
patches and fog at a distance)
- dust storm
- sandstorm
- funnel cloud
- moderate or heavy precipitation
Cloud
- When there is BKN or OVC cloud below the aerodrome’s highest
alternate minimum cloud base or 1500FT, whichever is greater*
Temperature
- When the temperature changes by 5°C or more since last report
Pressure
- When the QNH changes by 2hPa or more since last report
Other
- Upon receipt of advice of the existence of wind shear
- The incidence of any other phenomenon likely to be significant
