Section 7, Chapter 1 - Meteorological Services Flashcards
What is required for the briefing of controllers regarding weather before taking over a watch?
Weather Briefing for Controllers:
Requirement:
- Controllers must obtain full information about the expected weather during their watch before taking over.
Methods:
- Study forecasts and charts supplied routinely by the Met Office.
- If clarification is needed, receive a briefing from the designated forecast unit.
What does ‘cloud base’ mean in meteorological reports and aerodrome forecasts, and who is the Meteorological Authority for civil aviation in the UK?
Explanation of Terms:
Cloud Base:
- The height of the base of any cloud above aerodrome elevation in meteorological reports and aerodrome forecasts.
Meteorological Authority:
- The Civil Aviation Authority (CAA) is the Meteorological Authority for civil aviation in the United Kingdom, located at CAA House, 45–59 Kingsway, London WC2B 6TE.
What are the guidelines for controllers on supplying meteorological information to aircraft?
Supply of Meteorological Information:
Source of Information:
- Meteorological forecasting services to ATSUs are provided by the Met Office from Exeter or other designated forecast offices.
- Controllers generally transmit only information supplied or agreed by the Met Office, with the following exceptions:
- Indicated wind direction and speed from anemometer indicators in the control room.
- RVR (Runway Visual Range) observations.
- Sudden or unexpected deteriorations requiring immediate warning for safety, followed by consultation with the meteorological forecast office.
- Information from an aircraft in flight, if useful to other aircraft, stating the origin and time of observation.
- Special Aircraft Reports of meteorological conditions affecting safety.
- Cloud echoes observed on PSR (Primary Surveillance Radar).
- Observations made by personnel with a Meteorological Observing Certificate.
- Unofficial observations at aerodromes without accredited observers should be prefixed with: “Unofficial observation from (name of aerodrome) at (time) UTC gives (observation).”
Monitoring and Reporting:
- Controllers must keep a close watch on the weather and report sudden or unexpected changes to the duty observer or appropriate forecast office without delay.
- Controllers may be asked to obtain weather observations from aircraft.
What are the procedures for handling Special Aircraft Observations and Reports in aviation?
Special Aircraft Observations:
- Conditions Requiring Special Air-Reports:
- Moderate icing (MOD ICE) or severe icing (SEV ICE).
- Moderate turbulence (MOD TURB) or severe turbulence (SEV TURB).
- Severe mountain wave (SEV MTW).
- Thunderstorms with or without hail (TSGR or TS).
- Volcanic ash cloud (VA CLD or VA).
- Pre-eruption volcanic activity or volcanic eruption.
Reporting and Dissemination:
- Recording:
- ATS units use the model AIREP SPECIAL form (Appendix J or similar ANSP document) to record special and non-routine Air-Reports.
Dissemination:
- To Other Aircraft: Information is provided to other aircraft for the route up to one hour’s flying time ahead.
- To Met Office: Send the report to the Met Office at Exeter or Aberdeen, who will decide if a SIGMET is needed.
- To Other ATS Units: Inform ATS units with jurisdiction over airspace that affected flights are expected to enter.
Transmission Frequency:
- Repeat transmissions to aircraft at a frequency and for a duration determined by the ATS unit concerned.
Special Air-Report Content:
- Position or latitude and longitude.
- Time.
- Flight level or altitude.
- Meteorological information/conditions.
What steps should be taken by controllers to check weather information before transmission to aircraft?
Checking Weather Information:
Comparison:
- Compare current weather reports with previous reports and prevailing conditions.
Reconciling Differences:
- Confirm any difficult-to-reconcile differences with the duty meteorological observer.
- Verify barometric pressures that are inconsistent with the apparent tendency before transmitting to aircraft.
How should meteorological observers communicate routine and special reports to ATC, and how should special reports be identified on the aerodrome weather report form?
Communicating Meteorological Reports:
Method:
- The method for communicating routine and special reports to ATC is described in MATS Part 2.
Identifying Special Reports:
- Special reports should be clearly identified as such on the aerodrome weather report form or display.
- Elements of a routine report that show a specific change requiring a special report should be underlined or highlighted on the form or display.
What are the requirements for recording weather reports in aviation?
Recording Weather Reports:
Requirement:
- All weather reports, both routine and special, must be recorded in the Meteorological Register or by another method approved by the CAA.
Contingency Arrangements:
- Develop and follow contingency arrangements in case of equipment failure or non-availability used to record weather reports.
Variance Reporting:
- Record any information (except surface wind measurements) that is at variance with the official weather report and is passed to aircraft or operators in the approved manner.
What items are included in routine aerodrome meteorological reports, and how should wind direction be expressed in reports to aircraft for take-off and landing?
Routine Aerodrome Meteorological Reports:
Issued hourly or half-hourly and contain the following items:
Surface Wind:
* Direction in degrees True and speed in knots, averaged over 10 minutes.
* Extremes in direction if variation is 60 degrees or more and mean speed exceeds 3 knots.
* Maximum wind speed if it exceeds the mean by 10 knots or more.
Surface Visibility:
* Prevailing visibility in specified increments based on distance.
* RVR included when measured.
* Lowest visibility in any direction if less than prevailing visibility and less than 1,500 meters or 50% of the prevailing visibility.
Weather:
* Conditions at the time of observation (e.g., drizzle, fog, heavy rain).
Cloud:
* Layers reported as few, scattered, broken, or overcast with bases in feet, up to 5,000 ft above aerodrome elevation.
* Specific layers reported:
* Lowest individual layer.
* Next highest of at least 3 oktas.
* Next highest of at least 5 oktas.
* Towering cumulus and cumulonimbus always specified.
* ‘Sky obscured’ reported if cloud base is not discernible.
CAVOK:
* Used when visibility is 10 km or more, no significant weather at the aerodrome, and no cloud below 5,000 ft or minimum sector altitude, and no cumulonimbus or towering cumulus clouds.
QNH:
* Rounded down to the nearest whole Hectopascal.
QFE:
* Rounded down to the nearest whole Hectopascal. For multiple elevations, rounded to the nearest tenth and converted appropriately.
Air Temperature and Dew Point:
* Both values included.
Reports to Aircraft for Take-off and Landing:
* Wind direction expressed in degrees Magnetic.
* Averaging period of 2 minutes.
* Provide extremes in direction and speed (gust and lull) during the past 10 minutes.
What are the criteria for issuing special aerodrome meteorological reports, and what items do they include?
Special Aerodrome Meteorological Reports:
- Issued for specific improvements and deteriorations between routine reports, containing only the affected items.
Criteria for Special Reports:
Surface Wind:
- Change in mean direction of 60° or more with mean speed before/after change being 10 kt or more, or 30° change when 20 kt or more.
- Change in mean speed of 10 kt or more.
- Change in gust speed of 10 kt or more with mean speed before/after change being 15 kt or more.
Surface Visibility:
- Change between visibility ranges:
- 10 km or more
- 5,000 m to 9 km
- 3,000 m to 4,900 m
- 2,000 m to 2,900 m
- 1,500 m to 1,900 m
- 800 m to 1,400 m
- 750 m or less
- Minimum visibility becomes less than or greater than 50% of prevailing visibility.
- Minimum visibility changes between the specified ranges.
- Additional RVR changes if arrangements are made for non-available or unserviceable RVR:
- 600 to 750 m
- 350 to 550 m
- 150 to 300 m
- 125 m or less
Weather:
- Onset, cessation, or change in intensity of:
- Moderate or heavy precipitation (including showers)
- Freezing precipitation (any intensity)
- Freezing fog
- Thunderstorm (with or without precipitation)
- Funnel cloud (tornado or waterspout)
- Squall
- Low drifting or blowing snow, dust, or sand
Cloud:
- Base: When the base of the lowest cloud covering more than half the sky changes between:
- 2,000 ft or more
- 1,500 ft to 1,900 ft
- 1,000 ft to 1,400 ft
- 700 ft to 900 ft
- 500 ft to 600 ft
- 300 ft to 400 ft
- 200 ft to 100 ft
- Less than 100 ft (including sky obscured)
- Amount: When the amount of the lowest layer below 1,500 ft changes from half or less to more than half, and vice versa.
Pressure:
- When QNH or QFE changes by 1.0 Hectopascal or more.
Temperature:
- When air temperature changes by 2.0 degrees or more.
Severe Icing and/or Turbulence:
- When an aircraft on approach or climb out reports severe icing and/or severe turbulence, confirmed by the duty forecaster at the local meteorological forecast office.
What is a METAR and what information does it include or omit?
Coded Aerodrome Weather Reports (METAR):
Definition:
- METAR is a coded aerodrome weather report prepared routinely hourly or half-hourly by accredited meteorological observers.
Contents:
Includes:
* Weather information
* Recent weather of operational significance
* Runway state reports (when required)
Omits:
* QFE
* Any remarks
What are SIGMET messages, and what phenomena necessitate their issuance?
SIGMET Messages:
Purpose:
- Issued and disseminated via OPMET and AFTN for phenomena that may affect aircraft safety, reported or expected in a monitored area.
Content:
- Describes the phenomenon, its location, expected movements, expected development, and whether observed or forecast.
- Expressed in abbreviated plain language using ICAO-approved abbreviations.
- Each message refers to only one weather phenomenon.
- Numbered sequentially from 0001 UTC each day.
Validity:
- Typically valid for up to 4 hours, except for volcanic ash clouds (up to 12 hours).
- Re-issued if conditions persist beyond the original period.
- Can be amended when conditions change and cancelled when conditions cease.
Phenomena Necessitating SIGMET:
- Thunderstorm (including cumulonimbus clouds without a thunderstorm)
- Tropical cyclone
- Heavy hail
- Severe mountain waves
- Freezing rain
- Heavy dust or sandstorm
- Severe icing
- Volcanic ash cloud
- Severe turbulence
What is the process for Regional Pressure Setting forecasts?
The lowest QNH value for each Altimeter Setting Region is forecast and made available hourly for the period H + 1 to H + 2.
Who prepares and issues Area and Aerodrome Forecasts, and how are they managed?
Area forecasts (AIRMET) and coded aerodrome forecasts (TAFs and TRENDs) are prepared and issued by the Met Office as directed by the Meteorological Authority. They are updated routinely and may be amended as necessary.
What are the components of AIRMET regional and area forecast texts?
AIRMET regional and area forecast texts, prepared every 6 hours covering an 8-hour period with a 6-hour outlook, include:
- Meteorological (synoptic) situation
- Upper winds and temperatures at 1,000 ft, 3,000 ft, and 6,000 ft
- Height of 0°C isotherm
- Weather conditions (surface visibility, weather, and cloud amount, type, height of base and top)
- Weather warnings (strong winds and gales, turbulence, icing, mountain waves, or thunderstorms)
These forecasts are also available in chart format as Form 214 (spot wind) and Form 215 (low-level weather).
What are the key details regarding coded aerodrome forecasts (TAFs and TRENDs)?
- TAFs are prepared for aerodromes with regular coded aerodrome weather reports (METARs) by certified meteorological observers.
- TAFs cover periods of 9 hours, 24 hours, or 30 hours, issued approximately one hour before validity.
- Update periods: every 3 hours for 9-hour TAFs and every 6 hours for 24 or 30-hour TAFs.
- For selected aerodromes, landing forecasts (TRENDs) are added to each routine METAR to indicate significant changes expected over the next 2 hours.
