Commission Implementing Regulation (EU) 2017/373Show full title

SPECIFIC REQUIREMENTS FOR PROVIDERS OF METEOROLOGICAL SERVICES (Part-MET)

SUBPART A — ADDITIONAL ORGANISATION REQUIREMENTS FOR PROVIDERS OF METEOROLOGICAL SERVICES (MET.OR)

SECTION 1 — GENERAL REQUIREMENTS

MET.OR.100 Meteorological data and information

(a)

A meteorological services provider shall provide operators, flight crew members, air traffic services units, search and rescue services units, aerodrome operators, accident and incident investigation bodies, and other service providers and aviation entities with the meteorological information necessary for the performance of their respective functions, as determined by the competent authority.

(b)

A meteorological services provider shall confirm the operationally desirable accuracy of the information distributed for operations, including the source of such information, whilst also ensuring that such information is distributed in a timely manner and updated, as required.

MET.OR.105 Retention of meteorological information

(a)

A meteorological services provider shall retain meteorological information issued for a period of at least 30 days from the date of issue.

(b)

This meteorological information shall be made available, on request, for inquiries or investigations and, for these purposes, shall be retained until the inquiry or investigation is completed.

MET.OR.110 Meteorological information exchange requirements

A meteorological services provider shall ensure it has systems and processes in place, as well as access to suitable telecommunications facilities to:

(a)

enable the exchange of operational meteorological information with other meteorological services providers;

(b)

provide the required meteorological information to the users in a timely manner.

MET.OR.115 Meteorological bulletins

The meteorological services provider responsible for the area concerned shall provide meteorological bulletins to the relevant users, via the aeronautical fixed service or the internet.

MET.OR.120 Notification of discrepancies to the world area forecast centres (WAFC)

The meteorological services provider responsible for the area concerned shall, using WAFS BUFR data, notify the WAFC concerned immediately if significant discrepancies are detected or reported in respect of WAFS significant weather (SIGWX) forecasts, concerning:

(a)

icing, turbulence, cumulonimbus clouds that are obscured, frequent, embedded, or occurring at a squall line, and sandstorms/dust storms;

(b)

volcanic eruptions or a release of radioactive materials into the atmosphere of significance to aircraft operations.

SECTION 2 — SPECIFIC REQUIREMENTS

Chapter 1 — Requirements for aeronautical meteorological stations

MET.OR.200 Meteorological reports and other information

(a)

An aeronautical meteorological station shall disseminate:

(1)

local routine reports at fixed intervals, only for dissemination at the aerodrome of origin;

(2)

local special reports, only for dissemination at the aerodrome of origin;

(3)

METAR at half-hourly intervals at aerodromes serving scheduled international commercial air transport operations for dissemination beyond the aerodrome of origin.

(b)

An aeronautical meteorological station shall inform the air traffic service units and aeronautical information service of an aerodrome of changes in the serviceability status of the automated equipment used for assessing runway visual range.

(c)

An aeronautical meteorological station shall report to the associated air traffic services unit, aeronautical information services unit, and meteorological watch office the occurrence of pre-eruption volcanic activity, volcanic eruptions and volcanic ash cloud.

(d)

An aeronautical meteorological station shall establish a list of criteria to provide local special reports in consultation with the appropriate ATS units, operators and others concerned.

MET.OR.205 Reporting of meteorological elements

At aerodromes serving scheduled international commercial air transport operations, an aeronautical meteorological station shall report:

(a)

surface wind direction and speed;

(b)

visibility;

(c)

runway visual range, if applicable;

(d)

present weather at the aerodrome and its vicinity;

(e)

clouds;

(f)

air temperature and dew point temperature;

(g)

atmospheric pressure;

(h)

supplementary information when applicable.

Where authorised by the competent authority, at aerodromes not serving scheduled international commercial air transport operations, an aeronautical meteorological station may report only a subset of the meteorological elements as relevant to the types of flights at that aerodrome. This data set shall be published in the aeronautical information publication.

MET.OR.210 Observing meteorological elements

At aerodromes serving scheduled international commercial air transport operations, an aeronautical meteorological station shall observe and/or measure:

(a)

surface wind direction and speed;

(b)

visibility;

(c)

runway visual range, if applicable;

(d)

present weather at the aerodrome and its vicinity;

(e)

clouds;

(f)

air temperature and dew point temperature;

(g)

atmospheric pressure;

(h)

supplementary information, when applicable:

Where authorized by the competent authority, at aerodromes not serving scheduled international commercial air transport operations, an aeronautical meteorological station may observe and/or measure only a subset of the meteorological elements as relevant to the types of flights at that aerodrome. This data set shall be published in the aeronautical information publication.

Chapter 2 — Requirements for aerodrome meteorological offices

MET.OR.215 Forecasts and other information

An aerodrome meteorological office shall:

(a)

prepare and/or obtain forecasts and other relevant meteorological information necessary for the performance of its respective functions for flights with which it is concerned, as determined by the competent authority;

(b)

provide forecasts and/or warnings for local meteorological conditions on aerodromes for which it is responsible;

(c)

keep the forecasts and warnings under continuous review and issue amendments promptly when necessary, and cancel any forecast of the same type previously issued for the same place and for the same period of validity or part thereof;

(d)

provide briefing, consultation and flight documentation to flight crew members and/or other flight operations personnel;

(e)

provide climatological information;

(f)

provide its associated air traffic services unit, aeronautical information service unit and meteorological watch office with information received on pre-eruption volcanic activity, a volcanic eruption or volcanic ash cloud;

(g)

provide, if applicable, meteorological information to search and rescue services units and maintain liaison with the search and rescue services unit(s) throughout a search and rescue operation;

(h)

provide meteorological information to relevant aeronautical information services units, as necessary, for the conduct of their functions;

(i)

prepare and/or obtain forecast and other relevant meteorological information necessary for the performance of the ATS units functions in accordance with point MET.OR.242;

(j)

provide its associated air traffic services unit, aeronautical information service unit and meteorological watch offices with information received on the release of radioactive materials into the atmosphere.

MET.OR.220 Aerodrome forecasts

(a)

An aerodrome meteorological office shall issue aerodrome forecasts as a TAF at a specified time.

(b)

When issuing TAF, the aerodrome meteorological office shall ensure that not more than one TAF is valid at an aerodrome at any given time.

MET.OR.225 Forecasts for landing

(a)

An aerodrome meteorological office shall prepare forecasts for landing as determined by the competent authority.

(b)

This forecast for landing shall be issued in the form of a TREND forecast.

(c)

The period of validity of a TREND forecast shall be 2 hours from the time of the report which forms part of the landing forecast.

MET.OR.230 Forecasts for take-off

An aerodrome meteorological office shall:

(a)

prepare forecasts for take-off as determined by the competent authority;

(b)

supply forecasts for take-off to operators and flight crew members on request within the 3 hours before the expected time of departure.

MET.OR.235 Aerodrome warnings and wind shear warnings and alerts

An aerodrome meteorological office shall:

(a)

provide aerodrome warnings information;

(b)

prepare wind shear warnings for aerodromes where wind shear is considered a factor, in accordance with local arrangements with the appropriate ATS unit and operators concerned;

(c)

issue, at aerodromes where wind shear is detected by automated, ground-based, wind shear remote-sensing or detection equipment, wind shear alerts generated by these systems;

(d)

cancel warnings when the conditions are no longer occurring and/or no longer expected to occur at the aerodrome.

MET.OR.240 Information for use by operator or flight crew

(a)

An aerodrome meteorological office shall provide operators and flight crew members with:

(1)

forecasts, originating from the WAFS, of the elements listed in points (1) and (2) of point MET.OR.275(a);

(2)

METAR or SPECI, including TREND forecasts, TAF or amended TAF for the aerodromes of departure and intended landing, and for take-off, en-route and destination alternate aerodromes;

(3)

aerodrome forecasts for take-off;

(4)

SIGMET and special air-reports relevant to the whole route;

(5)

volcanic ash and tropical cyclone advisory information relevant to the whole route;

(6)

area forecasts for low-level flights in chart form prepared in support of the issuance of an AIRMET message, and an AIRMET message for low-level flights relevant to the whole route;

(7)

aerodrome warnings for the local aerodrome;

(8)

meteorological satellite images;

(9)

ground-based weather radar information.

(b)

Whenever the meteorological information to be included in the flight documentation differs materially from that made available for flight planning, the aerodrome meteorological office shall:

(1)

advise immediately the operator or flight crew concerned;

(2)

if practicable, provide the revised meteorological information in agreement with the operator.

MET.OR.242 Information to be provided to air traffic services units

(a)

An aerodrome meteorological office shall provide, as necessary, its associate aerodrome control tower with:

(1)

local routine and special reports, METAR, TAF and TREND forecasts and amendments thereto;

(2)

SIGMET and AIRMET information, wind shear warnings and alerts and aerodrome warnings;

(3)

any additional meteorological information agreed upon locally, such as forecasts of surface wind for the determination of possible runway changes;

(4)

information received on volcanic ash cloud, for which a SIGMET has not already been issued, as agreed between the aerodrome meteorological office and the aerodrome control tower concerned;

(5)

information received on pre-eruption volcanic activity and/or a volcanic eruption as agreed between the aerodrome meteorological office and the aerodrome control tower concerned.

(b)

An aerodrome meteorological office shall provide its associate approach control unit with:

(1)

local routine and special reports, METAR, TAF and TREND forecasts and amendments thereto;

(2)

SIGMET and AIRMET information, wind shear warnings and alerts and appropriate special air-reports and aerodrome warnings;

(3)

any additional meteorological information agreed upon locally;

(4)

information received on volcanic ash cloud, for which a SIGMET has not already been issued, as agreed between the aerodrome meteorological office and the approach control unit concerned;

(5)

information received on pre-eruption volcanic activity and/or a volcanic eruption as agreed between the aerodrome meteorological office and the approach control unit concerned.

Chapter 3 — Requirements for meteorological watch offices

MET.OR.245 Meteorological watch and other information

Within its area of responsibility, the meteorological watch office shall:

(a)

maintain continuous watch over meteorological conditions affecting flight operations;

(b)

coordinate with the organisation responsible for the provision of NOTAM and/or ASHTAM to ensure that meteorological information on volcanic ash included in SIGMET and NOTAM and/or ASHTAM messages is consistent;

(c)

coordinate with selected volcano observatories to ensure that information on volcanic activity is received in an efficient and timely manner;

(d)

provide its associated VAAC with information received on pre-eruption volcanic activity, a volcanic eruption and volcanic ash cloud for which a SIGMET has not already been issued;

(e)

provide its aeronautical information service units with information received on the release of radioactive materials into the atmosphere in the area or adjacent areas for which it maintains watch and for which a SIGMET has not already been issued;

(f)

provide its associated area control centre and flight information centre (ACC/FIC), as necessary, with relevant:

(1)

METAR, including current pressure data for aerodromes and other locations, TAF and trend forecasts and amendments thereto;

(2)

forecasts of upper winds, upper-air temperatures and significant en-route weather phenomena and amendments thereto, SIGMET and AIRMET information and appropriate special air-reports;

(3)

any other meteorological information required by the ACC/FIC to meet requests from aircraft in flight;

(4)

information received on volcanic ash cloud, for which a SIGMET has not already been issued, as agreed between the meteorological watch office and the ACC/FIC;

(5)

information received concerning the release of radioactive material into the atmosphere, as agreed between the meteorological watch office and the ACC/FIC;

(6)

tropical cyclone advisory information issued by a TCAC in its area of responsibility;

(7)

volcanic ash advisory information issued by a VAAC in its area of responsibility;

(8)

information received on pre-eruption volcanic activity and/or a volcanic eruption as agreed between the meteorological watch office and the ACC/FIC.

MET.OR.250 SIGMET messages

A meteorological watch office shall:

(a)

provide and disseminate SIGMET messages;

(b)

ensure that the SIGMET message is cancelled when the phenomena are no longer occurring or are no longer expected to occur in the area covered by the SIGMET message;

(c)

ensure that the period of validity of a SIGMET message is not more than 4 hours, and in the special case of SIGMET messages for volcanic ash cloud and tropical cyclones, it shall be extended up to 6 hours;

(d)

ensure that SIGMET messages are issued not more than 4 hours before the commencement of the period of validity, and in the special case of SIGMET messages for volcanic ash cloud and tropical cyclones, as soon as practicable, but not more than 12 hours before the commencement of the period of validity, and updated at least every 6 hours.

MET.OR.255 AIRMET messages

A meteorological watch office shall:

(a)

provide and disseminate AIRMET messages when the competent authority has determined that the density of traffic operating below flight level 100, or up to flight level 150 in mountainous areas, or higher, where necessary, warrants the issue and dissemination of area forecasts for such operations;

(b)

cancel the AIRMET message when the phenomena are no longer occurring or are no longer expected to occur in the area;

(c)

ensure that the period of validity of an AIRMET message is not more than 4 hours.

MET.OR.260 Area forecasts for low-level flights

A meteorological watch office shall:

(a)

provide area forecast for low-level flights when the density of traffic operating below flight level 100, or up to flight level 150 in mountainous areas, or higher, where necessary, warrants the routine issue and dissemination of area forecasts for such operations;

(b)

ensure that the frequency of issue, the form, and the fixed time or period of validity of area forecast for low-level flights and the criteria for amendments thereto, are as determined by the competent authority;

(c)

ensure that area forecasts for low-level flights prepared in support of the issuance of an AIRMET message are issued every 6 hours for a period of validity of 6 hours and transmitted to the meteorological watch offices concerned not later than 1 hour prior to the beginning of their validity period.

Chapter 4 — Requirements for volcanic ash advisory centre (VAAC)

MET.OR.265 Volcanic ash advisory centre responsibilities

In its area of responsibility, the VAAC shall:

(a)

when a volcano has erupted, or is expected to erupt, or volcanic ash is reported, provide advisory information regarding the extent and forecast movement of the volcanic ash cloud to:

(1)

the European aviation crisis coordination cell;

(2)

meteorological watch offices serving flight information regions in its area of responsibility which may be affected;

(3)

operators, area control centres, and flight information centres serving flight information regions in its area of responsibility which may be affected;

(4)

world area forecast centres, international OPMET databanks, international NOTAM offices and centres designated by regional air navigation agreement for the operation of aeronautical fixed service satellite distribution systems;

(5)

other VAACs whose areas of responsibility may be affected.

(b)

coordinate with selected volcano observatories to ensure that information on volcanic activity is received in an efficient and timely manner;

(c)

provide the advisory meteorological information referred to in point (a) at least every 6 hours until such time as the volcanic ash cloud is no longer identifiable from satellite data, no further meteorological reports of volcanic ash are received from the area and no further eruptions of the volcano are reported; and

(d)

maintain a 24-hour watch.

Chapter 5 — Requirements for tropical cyclone advisory centre (TCAC)

MET.OR.270 Tropical cyclone advisory centre responsibilities

A TCAC shall issue:

(a)

advisory information concerning the position of the cyclone centre, its direction and speed of movement, central pressure and maximum surface wind near the centre in abbreviated plain language to:

(1)

meteorological watch offices in its area of responsibility;

(2)

other TCACs whose areas of responsibility may be affected;

(3)

world area forecast centres, international OPMET databanks and centres responsible for the operation of aeronautical fixed service satellite distribution systems;

(b)

updated advisory information to meteorological watch offices for each tropical cyclone, as necessary, but at least every 6 hours.

Chapter 6 — Requirements for world area forecast centre (WAFC)

MET.OR.275 World area forecast centre responsibilities

(a)

The WAFC shall provide, in a digital form:

(1)

gridded global forecasts of:

(i)

upper wind;

(ii)

upper-air temperature and humidity;

(iii)

geopotential altitude of flight levels;

(iv)

flight level and temperature of tropopause;

(v)

direction, speed and flight level of maximum wind;

(vi)

cumulonimbus clouds;

(vii)

icing;

(viii)

turbulence;

(2)

global forecasts of significant weather (SIGWX) phenomena, including volcanic activity and release of radioactive materials.

(b)

The WAFC shall ensure that world area forecast system products in digital form are transmitted using binary data communications techniques.

SUBPART B — TECHNICAL REQUIREMENTS FOR PROVIDERS OF METEOROLOGICAL SERVICES (MET.TR)

SECTION 1 — GENERAL REQUIREMENTS

MET.TR.115 Meteorological bulletins

(a)

Meteorological bulletins shall contain a heading consisting of:

(1)

an identifier of four letters and two figures;

(2)

the ICAO four-letter location indicator corresponding to the geographical location of the meteorological service provider originating or compiling the meteorological bulletin;

(3)

a day-time group;

(4)

if required, a three-letter indicator.

(b)

Meteorological bulletins containing operational meteorological information to be transmitted via the AFTN shall be encapsulated in the text part of the AFTN message format.

SECTION 2 — SPECIFIC REQUIREMENTS

Chapter 1 — Technical requirements for aeronautical meteorological stations

MET.TR.200 Meteorological reports and other information

(a)

Local routine and local special reports and METAR shall contain the following elements in the order indicated:

(1)

identification of the type of report;

(2)

location indicator;

(3)

time of the observation;

(4)

identification of an automated or missing report, when applicable;

(5)

surface wind direction and speed;

(6)

visibility;

(7)

runway visual range, when the reporting criteria are met;

(8)

present weather;

(9)

cloud amount, cloud type only for cumulonimbus and towering cumulus clouds and height of cloud base or, where measured, vertical visibility;

(10)

air temperature and dew-point temperature;

(11)

QNH and, when applicable, in local routine and local special reports, QFE;

(12)

supplementary information, when applicable.

(b)

In local routine and local special reports:

(1)

if the surface wind is observed from more than one location along the runway, the locations for which these values are representative shall be indicated;

(2)

when there is more than one runway in use and the surface wind related to these runways is observed, the available wind values for each runway shall be given, and the runways to which the values refer shall be reported;

(3)

when variations from the mean wind direction are reported in accordance with point MET.TR.205(a)(3)(ii)(B), the two extreme directions between which the surface wind has varied shall be reported;

(4)

when variations from the mean wind speed (gusts) are reported in accordance with point MET.TR.205(a)(3)(iii), they shall be reported as the maximum and minimum values of the wind speed attained.

(c)

METAR

(1)

METAR shall be issued in accordance with the template shown in Appendix 1 and disseminated in the METAR code form prescribed by the World Meteorological Organisation.

(2)

If disseminated in digital form, METAR shall be:

(i)

formatted in accordance with a globally interoperable information exchange model and shall use geography markup language (GML);

(ii)

accompanied by the appropriate metadata.

(3)

METAR shall be filed for transmission not later than 5 minutes after the actual time of observation.

(d)

Information on visibility, runway visual range, present weather and cloud amount, cloud type and height of cloud base shall be replaced in all meteorological reports by the term ‘CAVOK’ when the following conditions occur simultaneously at the time of observation:

(1)

visibility, 10 km or more, and the lowest visibility is not reported;

(2)

no cloud of operational significance;

(3)

no weather of significance to aviation.

(e)

The list of criteria to provide local special reports shall include:

(1)

those values which most closely correspond to the operating minima of the operators using the aerodrome;

(2)

those values which satisfy other local requirements of the ATS units and of the operators;

(3)

an increase in air temperature of 2 °C or more from that given in the latest local report, or an alternative threshold value as agreed between the meteorological service providers, the appropriate ATS unit and the operators concerned;

(4)

the available supplementary information concerning the occurrence of significant meteorological conditions in the approach and climb-out areas;

(5)

when noise abatement procedures are applied and the variation from the mean surface wind speed has changed by 5 kt (2,5 m/s) or more from that at the time of the latest local report, the mean speed before and/or after the change being 15 kt (7,5 m/s) or more;

(6)

when the mean surface wind direction has changed by 60° or more from that given in the latest report, the mean speed before and/or after the change being 10 kt (5 m/s) or more;

(7)

when the mean surface wind speed has changed by 10 kt (5 m/s) or more from that given in the latest local report;

(8)

when the variation from the mean surface wind speed (gusts) has changed by 10 kt (5 m/s) or more from that at the time of the latest local report, the mean speed before and/or after the change being 15 kt (7,5 m/s) or more;

(9)

when the onset, cessation or change in intensity of any of the following weather phenomena occurs:

(i)

freezing precipitation;

(ii)

moderate or heavy precipitation, including showers thereof; and

(iii)

thunderstorm, with precipitation;

(10)

when the onset or cessation of any of the following weather phenomena occurs:

(i)

freezing fog;

(ii)

thunderstorm, without precipitation;

(11)

when the amount of a cloud layer below 1 500 ft (450 m) changes:

(i)

from scattered (SCT) or less to broken (BKN) or overcast (OVC); or

(ii)

from BKN or OVC to SCT or less.

(f)

When so agreed between the meteorological services provider and the competent authority, local special reports shall be issued whenever the following changes occur:

(1)

when the wind changes through values of operational significance. The threshold values shall be established by the meteorological service provider in consultation with the appropriate ATS unit and operators concerned, taking into account changes in the wind which would:

(i)

require a change in runway(s) in use;

(ii)

indicate that the runway tailwind and crosswind components have changed through values representing the main operating limits for typical aircraft operating at the aerodrome;

(2)

when the visibility is improving and changes to or passes through one or more of the following values, or when the visibility is deteriorating and passes through one or more of the following values:

(i)

800, 1 500 or 3 000 m;

(ii)

5 000 m, in cases where significant numbers of flights are operated in accordance with the visual flight rules;

(3)

when the runway visual range is improving and changes to or passes through one or more of the following values, or when the runway visual range is deteriorating and passes through one or more of the following values: 50, 175, 300, 550 or 800 m;

(4)

when the onset, cessation or change in intensity of any of the following weather phenomena occurs:

(i)

dust storm;

(ii)

sandstorm;

(iii)

funnel cloud (tornado or waterspout);

(5)

when the onset or cessation of any of the following weather phenomena occurs:

(i)

low drifting dust, sand or snow;

(ii)

blowing dust, sand or snow;

(iii)

squall;

(6)

when the height of base of the lowest cloud layer of BKN or OVC extent is lifting and changes to or passes through one or more of the following values, or when the height of base of the lowest cloud layer of BKN or OVC extent is lowering and passes through one or more of the following values:

(i)

100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m);

(ii)

1 500 ft (450 m), in cases where significant numbers of flights are operated in accordance with the visual flight rules;

(7)

when the sky is obscured and the vertical visibility is improving and changes to or passes through one or more of the following values, or when the vertical visibility is deteriorating and passes through one or more of the following values: 100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m);

(8)

any other criteria based on local aerodrome operating minima, as agreed between the meteorological services providers and the operators.

MET.TR.205 Reporting of meteorological elements

(a) Surface wind direction and speed

(1)

In local routine and local special reports and in METAR, the surface wind direction and speed shall be reported in steps of 10 degrees true and 1 kt (0,5 m/s) respectively.

(2)

Any observed value that does not fit the reporting scale in use shall be rounded to the nearest step in the scale.

(3)

In local routine and local special reports and in METAR:

(i)

the units of measurement used for the wind speed shall be indicated;

(ii)

variations from the mean wind direction during the past 10 minutes shall be reported as follows, if the total variation is 60° or more, alternatively:

(A)

when the total variation is 60° or more and less than 180° and the wind speed is 3 kt (1,5 m/s) or more, such directional variations shall be reported as the two extreme directions between which the surface wind has varied;

(B)

when the total variation is 60° or more and less than 180° and the wind speed is less than 3 kt (1,5 m/s), the wind direction shall be reported as variable with no mean wind direction;

(C)

when the total variation is 180° or more, the wind direction shall be reported as variable with no mean wind direction;

(iii)

variations from the mean wind speed (gusts), during the past 10 minutes shall be reported when the maximum wind speed exceeds the mean speed by, alternatively:

(A)

5 kt (2,5 m/s) or more in local routine and local special reports when noise abatement procedures are applied;

(B)

10 kt (5 m/s) or more otherwise;

(iv)

when a wind speed of less than 1 kt (0,5 m/s) is reported, it shall be indicated as calm;

(v)

when a wind speed of 100 kt (50 m/s) or more is reported, it shall be indicated to be more than 99 kt (49 m/s);

(vi)

when variations from the mean wind speed (gusts) are reported in accordance with point MET.TR.205(a), the maximum value of the wind speed attained shall be reported;

(vii)

when the 10-minute period includes a marked discontinuity in the wind direction and/or speed, only variations from the mean wind direction and mean wind speed occurring since the discontinuity shall be reported.

(b) Visibility

(1)

In local routine and local special reports and in METAR, the visibility shall be reported in steps of 50 m when the visibility is less than 800 m; in steps of 100 m when it is 800 m or more, but less than 5 km; in kilometre steps when the visibility is 5 km or more, but less than 10 km; and it shall be given as 10 km when the visibility is 10 km or more, except when the conditions for the use of CAVOK apply.

(2)

Any observed value which does not fit the reporting scale in use shall be rounded down to the nearest lower step in the scale.

(3)

In local routine and local special reports, visibility along the runway(s) shall be reported together with the units of measurement used to indicate visibility.

(c) Runway visual range (RVR)

(1)

In local routine and local special reports and in METAR, the RVR shall be reported in steps of 25 m when it is less than 400 m; in steps of 50 m when it is between 400 and 800 m; and in steps of 100 m when it is more than 800 m.

(2)

Any observed value which does not fit the reporting scale in use shall be rounded down to the nearest lower step in the scale.

(3)

In local routine and local special reports and in METAR:

(i)

when the RVR is above the maximum value that can be determined by the system in use, it shall be reported using the abbreviation ‘ABV’ in local routine and local special reports, and the abbreviation ‘P’ in METAR followed by the maximum value that can be determined by the system;

(ii)

when the RVR is below the minimum value that can be determined by the system in use, it shall be reported using the abbreviation ‘BLW’ in local routine and local special reports, and the abbreviation ‘M’ in METAR, followed by the minimum value that can be determined by the system.

(4)

In local routine and local special reports:

(i)

the units of measurement used shall be included;

(ii)

if the RVR is observed from only one location along the runway, such as the touchdown zone, it shall be included without any indication of location;

(iii)

if the RVR is observed from more than one location along the runway, the value representative of the touchdown zone shall be reported first, followed by the values representative of the mid-point and stop-end, and the locations for which these values are representative shall be indicated;

(iv)

when there is more than one runway in use, the available RVR values for each runway shall be reported, and the runways to which the values refer shall be indicated.

(d) Present weather phenomena

(1)

In local routine and local special reports, observed present weather phenomena shall be reported in terms of type and characteristics and qualified with respect to intensity, as appropriate.

(2)

In METAR, observed present weather phenomena shall be reported in terms of type and characteristics and qualified with respect to intensity or proximity to the aerodrome, as appropriate.

(3)

In local routine and local special reports and in METAR, the following characteristics of present weather phenomena, as necessary, shall be reported using their respective abbreviations and relevant criteria, as appropriate:

(i)

Thunderstorm (TS)

Used to report a thunderstorm with precipitation. When thunder is heard or lightning is detected at the aerodrome during the 10-minute period preceding the time of observation but no precipitation is observed at the aerodrome, the abbreviation ‘TS’ shall be used without qualification.

(ii)

Freezing (FZ)

Supercooled water droplets or precipitation, used with types of present weather phenomena in accordance with Appendix 1.

(4)

In local routine and local special reports and in METAR:

(i)

one or more, up to a maximum of three, of the present weather abbreviations shall be used, as necessary, together with an indication, where appropriate, of the characteristics and intensity or proximity to the aerodrome, so as to convey a complete description of the present weather of significance to flight operations;

(ii)

the indication of intensity or proximity, as appropriate, shall be reported first followed respectively by the characteristics and the type of weather phenomena;

(iii)

where two different types of weather are observed, they shall be reported in two separate groups, where the intensity or proximity indicator refers to the weather phenomenon which follows the indicator. However, different types of precipitation occurring at the time of observation shall be reported as one single group with the dominant type of precipitation reported first and preceded by only one intensity qualifier which refers to the intensity of the total precipitation.

(e) Clouds

(1)

In local routine and local special reports and in METAR, the height of cloud base shall be reported in steps of 100 ft (30 m) up to 10 000 ft (3 000 m).

(2)

Any observed value which does not fit the reporting scale in use shall be rounded down to the nearest lower step in the scale.

(3)

In local routine and local special reports:

(i)

the units of measurement used for the height of cloud base and vertical visibility shall be indicated;

(ii)

when there is more than one runway in use and the heights of cloud bases are observed by instruments for these runways, the available heights of cloud bases for each runway shall be reported, and the runways to which the values refer shall be indicated.

(f) Air temperature and dew-point temperature

(1)

In local routine and local special reports and in METAR, the air temperature and the dew-point temperature shall be reported in steps of whole degrees Celsius.

(2)

Any observed value which does not fit the reporting scale in use shall be rounded to the nearest whole degree Celsius, with observed values involving 0,5° rounded up to the next higher whole degree Celsius.

(3)

In local routine and local special reports and in METAR, a temperature below 0 °C shall be identified.

(g) Atmospheric pressure

(1)

In local routine and local special reports and in METAR, QNH and QFE shall be computed in tenths of hectopascals and reported therein in steps of whole hectopascals, using four digits.

(2)

Any observed value which does not fit the reporting scale in use shall be rounded down to the nearest lower whole hectopascal.

(3)

In local routine and local special reports:

(i)

QNH shall be included;

(ii)

QFE shall be included if required by users or, if so agreed locally between the provider of meteorological services, the ATS unit and the operators concerned, on a regular basis;

(iii)

the units of measurement used for QNH and QFE values shall be included;

(iv)

if QFE values are required for more than one runway, the required QFE values for each runway shall be reported, and the runway(s) to which the values refer shall be indicated.

(4)

In METAR, only QNH values shall be included.

MET.TR.210 Observing meteorological elements

The following meteorological elements shall be observed and/or measured with specified accuracy and disseminated by automatic or semi-automatic meteorological observing system.

(a) Surface wind direction and speed

The mean direction and the mean speed of the surface wind shall be measured, as well as significant variations of the wind direction and speed (gusts), and reported in degrees true and knots, respectively.

(1) Siting

The meteorological instrument used to measure surface wind direction and speed shall be situated in such a way as to provide data which is representative of the area for which the measurements are required.

(2) Display

Surface wind displays relating to each sensor shall be located in the meteorological station. The displays in the meteorological station and in the air traffic services units shall relate to the same sensors, and where separate sensors are required, the displays shall be clearly marked to identify the runway and section of runway monitored by each sensor.

(3) Averaging

The averaging period for surface wind observations shall be:

(i)

2 minutes for local routine and local special reports and for wind displays in ATS units;

(ii)

10 minutes for METAR, except that when the 10-minute period includes a marked discontinuity in the wind direction and/or speed; only data occurring after the discontinuity shall be used for obtaining mean values; hence, the time interval in these circumstances shall be correspondingly reduced.

(b) Visibility

(1) The visibility shall be measured or observed, and reported in metres or kilometres.

(2) Siting

The meteorological instrument used to measure visibility shall be situated in such a way as to supply data which is representative of the area for which the measurements are required.

(3) Displays

When instrumented systems are used for the measurement of visibility, visibility displays relating to each sensor shall be located in the meteorological station. The displays in the meteorological station and in the air traffic services units shall relate to the same sensors, and where separate sensors are required, the displays shall be clearly marked to identify the area monitored by each sensor.

(4) Averaging

The averaging period shall be 10 minutes for METAR, except that when the 10-minute period immediately preceding the observation includes a marked discontinuity in the visibility, only those values occurring after the discontinuity shall be used for obtaining mean values.

(c) Runway visual range (RVR)

(1) Siting

The meteorological instrument used to assess the RVR shall be situated in such a way as to provide data which is representative of the area for which the observations are required.

(2) Instrumented systems

Instrumented systems based on transmissometers or forward-scatter meters shall be used to assess RVR on runways intended for Categories II and III instrument approach and landing operations, and for Category I instrument approach and landing operations as determined by the competent authority.

(3) Display

Where the RVR is determined by instrumented systems, one display or more, if required, shall be located in the meteorological station. The displays in the meteorological station and in the air traffic services units shall relate to the same sensors, and where separate sensors are required, the displays shall be clearly marked to identify the runway and section of runway monitored by each sensor.

(4) Averaging

(i)

Where instrumented systems are used for the assessment of the RVR, their output shall be updated at least every 60 seconds to permit the provision of current, representative values.

(ii)

The averaging period for RVR values shall be:

(A)

1 minute for local routine and special reports and for RVR displays in ATS units;

(B)

10 minutes for METAR, except that when the 10-minute period immediately preceding the observation includes a marked discontinuity in RVR values; then only those values occurring after the discontinuity shall be used for obtaining mean values.

(d) Present weather phenomena

(1) The following present weather phenomena shall be reported, as a minimum: rain, drizzle, snow and freezing precipitation, including intensity thereof, haze, mist, fog, freezing fog and thunderstorms, including thunderstorms in the vicinity.

(2) Siting

The meteorological instrument used to measure present weather at the aerodrome and its vicinity shall be situated in such a way as to provide data which is representative of the area for which the measurements are required.

(e) Clouds

(1) Cloud amount, cloud type and height of cloud base shall be observed and reported as necessary to describe the clouds of operational significance. When the sky is obscured, vertical visibility shall be observed and reported, where measured, instead of cloud amount, cloud type and height of cloud base. The height of cloud base and vertical visibility shall be reported in feet.

(2) Siting

The meteorological instrument used to measure clouds amount and height shall be situated in such a way as to provide data which is representative of the area for which the measurements are required.

(3) Display

When automated equipment is used for the measurement of the height of cloud base, at least one display shall be located in the meteorological station. The displays in the meteorological station and in the air traffic services units shall relate to the same sensors, and where separate sensors are required, the displays shall be clearly marked to identify the area monitored by each sensor.

(4) Reference level

(i)

The height of cloud base shall be reported above aerodrome elevation.

(ii)

When a precision approach runway in use has a threshold elevation of 50 ft (15 m) or more below the aerodrome elevation, local arrangements shall be made in order that the height of cloud bases reported to arriving aircraft shall refer to the threshold elevation.

(iii)

In the case of reports from offshore structures, the height of cloud base shall be given above mean sea level.

(f) Air temperature and dew-point temperature

(1)

The air temperature and dew-point temperature shall be measured, displayed and reported in degrees Celsius.

(2)

When automated equipment is used for the measurement of air temperature and dew-point temperature, the displays shall be located in the meteorological station. The displays in the meteorological station and in the air traffic services units shall relate to the same sensors.

(g) Atmospheric pressure

(1) The atmospheric pressure shall be measured, and QNH and QFE values shall be computed and reported in hectopascals.

(2) Display

(i)

When automated equipment is used for the measurement of atmospheric pressure, QNH and, if required in accordance with point MET.TR.205(g)(3)(ii), QFE displays relating to the barometer shall be located in the meteorological station with corresponding displays in the appropriate air traffic services units.

(ii)

When QFE values are displayed for more than one runway, the displays shall be clearly marked to identify the runway to which the QFE value displayed refers.

(3) Reference level

A reference level for the computation of QFE shall be used.

Chapter 2 — Technical requirements for aerodrome meteorological offices

MET.TR.215 Forecast and other information

(a)

Meteorological information for operators and flight crew members shall:

(1)

cover the flight in respect of time, altitude and geographical extent;

(2)

relate to appropriate fixed times or periods of time;

(3)

extend to the aerodrome of intended landing, also covering the meteorological conditions expected between the aerodrome of intended landing and alternate aerodromes designated by the operator;

(4)

be up to date.

(b)

Meteorological information provided to rescue coordination centres shall include the meteorological conditions that existed in the last known position of a missing aircraft and along the intended route of that aircraft with particular reference to elements which are not being distributed routinely.

(c)

Meteorological information provided to aeronautical information services units shall include:

(1)

information on meteorological service intended for inclusion in the aeronautical information publication(s) concerned;

(2)

information necessary for the preparation of NOTAM or ASHTAM;

(3)

information necessary for the preparation of aeronautical information circulars.

(d)

Meteorological information included in flight documentation shall be represented as follows:

(1)

winds on charts shall be depicted by arrows with feathers and shaded pennants on a sufficiently dense grid;

(2)

temperatures shall be depicted by figures on a sufficiently dense grid;

(3)

wind and temperature data selected from the data sets received from a world area forecast centre shall be depicted in a sufficiently dense latitude/longitude grid;

(4)

wind arrows shall take precedence over temperatures and chart background;

(5)

height indications referring to en-route meteorological conditions shall be expressed as determined to be appropriate for the situation, for instance in flight levels, pressure, altitude or height above ground level, whilst all references referring to aerodrome meteorological conditions shall be expressed in height above the aerodrome elevation.

(e)

Flight documentation shall comprise:

(1)

forecasts of upper-wind and upper-air temperature;

(2)

SIGWX phenomena;

(3)

METAR or, when issued, SPECI for the aerodromes of departure and intended landing, and for take-off, en-route and destination alternate aerodromes;

(4)

TAF or amended TAF for the aerodromes of departure and intended landing, and for take-off, en-route and destination alternate aerodromes;

(5)

a SIGMET message, and, when issued, an AIRMET message and appropriate special air-reports relevant to the whole route;

(6)

volcanic ash and tropical cyclone advisory information relevant to the whole route.

However, when agreed between the aerodrome meteorological office and the operators concerned, flight documentation for flights of two hours' duration or less, after a short stop or turnaround, may be limited to the information operationally needed, but in all cases the flight documentation shall at least comprise the meteorological information listed in points (3), (4), (5) and (6).

(f)

Charts generated from digital forecasts shall be made available, as required by operators, for fixed areas of coverage as shown in Appendix 2.

(g)

When forecasts of upper-wind and upper-air temperature listed under point MET.OR.275(a)(1) are supplied in chart form, they shall be fixed-time prognostic charts for flight levels as specified in points MET.TR.260(b), MET.TR.275(c) and MET.TR.275(d). When forecasts of SIGWX phenomena listed under point MET.OR.275(a)(2) are supplied in chart form, they shall be fixed-time prognostic charts for an atmospheric layer limited by flight levels as specified in point MET.TR.275(b)(3).

(h)

The forecasts of upper-wind and upper-air temperature and of SIGWX phenomena above flight level 100 shall be supplied as soon as they become available, but not later than 3 hours before departure.

(i)

Aeronautical climatological information shall be prepared in the form of aerodrome climatological tables and aerodrome climatological summaries.

MET.TR.220 Aerodrome forecasts

(a)

Aerodrome forecasts and amendments thereto shall be issued as a TAF and shall include, in the order indicated, the:

(1)

identification of the type of forecast;

(2)

location indicator;

(3)

time of issue of forecast;

(4)

identification of a missing forecast, when applicable;

(5)

date and period of validity of forecast;

(6)

identification of a cancelled forecast, when applicable;

(7)

surface wind;

(8)

visibility;

(9)

weather;

(10)

cloud;

(11)

expected significant changes to one or more of these elements during the period of validity.

(b)

TAF shall be issued in accordance with the template shown in Appendix 3 and disseminated in the TAF code form.

(c)

The period of validity of a routine TAF shall be either 9 or 24 or 30 hours and shall be filed for transmission not earlier than 1 hour before the commencement of their period of validity.

(d)

TAF, if disseminated in digital form, shall:

(1)

be formatted in accordance with a globally interoperable information exchange model;

(2)

use geography markup language (GML);

(3)

be accompanied by the appropriate metadata.

(e)

The meteorological elements included in TAF shall be:

(1) Surface wind

(i)

In forecasting surface wind, the expected prevailing direction shall be given.

(ii)

When it is not possible to forecast a prevailing surface wind direction due to its expected variability, the forecasted wind direction shall be indicated as variable using ‘VRB’.

(iii)

When the wind is forecasted to be less than 1 kt (0,5 m/s), the forecasted wind speed shall be indicated as calm.

(iv)

When the forecasted maximum speed exceeds the forecasted mean wind speed by 10 kt (5 m/s) or more, the forecasted maximum wind speed shall be indicated.

(v)

When a wind speed of 100 kt (50 m/s) or more is forecasted, it shall be indicated to be more than 99 kt (49 m/s).

(2) Visibility

(i)

When the visibility is forecasted to be less than 800 m, it shall be expressed in steps of 50 m; when it is forecasted to be 800 m or more, but less than 5 km, in steps of 100 m; when it is forecasted to be 5 km or more, but less than 10 km, in kilometre steps; and when it is forecasted to be 10 km or more, it shall be expressed as 10 km, except when conditions of CAVOK are forecasted to apply. The prevailing visibility shall be forecasted.

(ii)

When visibility is forecasted to vary in different directions and the prevailing visibility cannot be forecasted, the lowest forecasted visibility shall be given.

(3) Weather phenomena

(i)

One or more, up to a maximum of three, of the following weather phenomena or combinations thereof, together with their characteristics and, where appropriate, intensity, shall be forecasted if they are expected to occur at the aerodrome:

(A)

freezing precipitation;

(B)

freezing fog;

(C)

moderate or heavy precipitation (including showers thereof);

(D)

low drifting dust, sand or snow;

(E)

blowing dust, sand or snow;

(F)

dust storm;

(G)

sandstorm;

(H)

thunderstorm (with or without precipitation);

(I)

squall;

(J)

funnel cloud (tornado or waterspout);

(K)

other weather phenomena, as agreed by the aerodrome meteorological office with the ATS units and operators concerned.

(ii)

The expected end of occurrence of those phenomena shall be indicated by the abbreviation ‘NSW’.

(4) Cloud

(i)

The cloud amount shall be forecast using the abbreviations ‘FEW’, ‘SCT’, ‘BKN’ or ‘OVC’, as necessary. When it is expected that the sky will remain or become obscured and clouds cannot be forecasted and information on vertical visibility is available at the aerodrome, the vertical visibility shall be forecasted in the form ‘VV’ followed by the forecasted value of the vertical visibility.

(ii)

When several layers or masses of cloud are forecasted, their amount and height of base shall be included in the following order:

(A)

the lowest layer or mass regardless of amount, to be forecasted as FEW, SCT, BKN or OVC as appropriate;

(B)

the next layer or mass covering more than 2/8, to be forecast as SCT, BKN or OVC as appropriate;

(C)

the next higher layer or mass covering more than 4/8, to be forecast as BKN or OVC as appropriate;

(D)

cumulonimbus clouds and/or towering cumulus clouds, whenever forecasted and not already included under points (A) to (C).

(iii)

Cloud information shall be limited to cloud of operational significance; when no cloud of operational significance is forecasted and ‘CAVOK’ is not appropriate, the abbreviation ‘NSC’ shall be used.

(f)

Use of change groups

(1)

The criteria used for the inclusion of change groups in TAF or for the amendment of TAF shall be based on any of the following weather phenomena, or combinations thereof, being forecasted to begin or end or change in intensity:

(i)

freezing fog;

(ii)

freezing precipitation;

(iii)

moderate or heavy precipitation (including showers thereof);

(iv)

thunderstorm;

(v)

dust storm;

(vi)

sandstorm.

(2)

When a change in any of the elements given in point (a) is required to be indicated, the change indicators ‘BECMG’ or ‘TEMPO’ shall be used followed by the time period during which the change is expected to occur. The time period shall be indicated as the beginning and end of the period in whole hours UTC. Only those elements for which a significant change is expected shall be included following a change indicator. However, in the case of significant changes in respect of cloud, all cloud groups, including layers or masses not expected to change, shall be indicated.

(3)

The change indicator ‘BECMG’ and the associated time group shall be used to describe changes where the meteorological conditions are expected to reach or pass through specified threshold values at a regular or irregular rate and at an unspecified time during the time period. The time period shall not exceed 4 hours.

(4)

The change indicator ‘TEMPO’ and the associated time group shall be used to describe expected frequent or infrequent temporary fluctuations in the meteorological conditions which reach or pass specified threshold values and last for a period of less than 1 hour in each instance and, in the aggregate, cover less than one half of the forecast period during which the fluctuations are expected to occur. If the temporary fluctuation is expected to last 1 hour or longer, the change group ‘BECMG’ shall be used in accordance with point (3), or the validity period should be subdivided in accordance with point (5).

(5)

Where one set of prevailing weather conditions is expected to change significantly and more or less completely to a different set of conditions, the period of validity shall be subdivided into self-contained periods using the abbreviation ‘FM’ followed immediately by a six-figure time group in days, hours and minutes UTC indicating the time the change is expected to occur. The subdivided period following the abbreviation ‘FM’ shall be self-contained and all forecasted conditions given before the abbreviation shall be superseded by those following the abbreviation.

(g)

The probability of occurrence of an alternative value of a forecast element or elements shall be included when:

(1)

a 30 or 40 % probability of alternative meteorological conditions exists during a specific forecast time period; or

(2)

a 30 or 40 % probability of temporary fluctuations in meteorological conditions exists during a specific forecast time period.

This shall be indicated in the TAF by using the abbreviation ‘PROB’ followed by the probability in tens of per cent and, in the case referred to in point (1), the time period during which the values are expected to apply, or in the case referred to in point (2), by using the abbreviation ‘PROB’ followed by the probability in tens of per cent, the change indicator ‘TEMPO’ and associated time group.

MET.TR.225 Forecasts for landing

(a)

TREND forecasts shall be issued in accordance with Appendix 1.

(b)

The units and scales used in the TREND forecast shall be the same as those used in the report to which it is appended.

(c)

The TREND forecast shall indicate significant changes in respect of one or more of the elements: surface wind, visibility, weather phenomena and clouds. Only those elements for which a significant change is expected shall be included. However, in the case of significant changes in respect of cloud, all cloud groups, including layers or masses not expected to change, shall be indicated. In the case of a significant change in visibility, the phenomenon causing the reduction of visibility shall also be indicated. When no change is expected to occur, this shall be indicated by the term ‘NOSIG’.

(1) Surface wind

The TREND forecast shall indicate changes in the surface wind which involve:

(i)

a change in the mean wind direction of 60° or more, the mean speed before and/or after the change being 10 kt (5 m/s) or more;

(ii)

a change in mean wind speed of 10 kt (5 m/s) or more;

(iii)

changes in the wind through values of operational significance.

(2) Visibility

(i)

When the visibility is expected to improve and change to or pass through one or more of the following values, or when the visibility is expected to deteriorate and pass through one or more of the following values: 150, 350, 600, 800, 1 500 or 3 000 m, the trend forecast shall indicate the change.

(ii)

When significant numbers of flights are conducted in accordance with the visual flight rules, the forecast shall additionally indicate changes to or passing through 5 000 m.

(iii)

In TREND forecasts appended to METAR, visibility shall refer to the forecast prevailing visibility.

(3) Weather phenomena

(i)

The TREND forecast shall indicate the expected onset, cessation or change in intensity of any of the following weather phenomena or combinations thereof:

(A)

freezing precipitation;

(B)

moderate or heavy precipitation, including showers thereof;

(C)

thunderstorm, with precipitation;

(D)

dust storm;

(E)

sandstorm;

(F)

other weather phenomena as agreed by the aerodrome meteorological office with the ATS units and operators concerned.

(ii)

The TREND forecast shall indicate the expected onset or cessation of any of the following weather phenomena or combinations thereof:

(A)

freezing fog;

(B)

low drifting dust, sand or snow;

(C)

blowing dust, sand or snow;

(D)

thunderstorm (without precipitation);

(E)

squall;

(F)

funnel cloud (tornado or waterspout).

(iii)

The total number of phenomena reported in points (i) and (ii) shall not exceed three.

(iv)

The expected end of occurrence of the weather phenomena shall be indicated by the abbreviation ‘NSW’.

(4) Clouds

(i)

When the height of base of a cloud layer of BKN or OVC extent is expected to lift and change to or pass through one or more of the following values, or when the height of base of a cloud layer of BKN or OVC extent is expected to lower and pass through one or more of the following values: 100, 200, 500, 1 000 and 1 500 ft (30, 60, 150, 300 and 450 m), the TREND forecast shall indicate the change.

(ii)

When the height of base of a cloud layer is below or is expected to fall below or rise above 1 500 ft (450 m), the TREND forecast shall also indicate changes in cloud amount from FEW, or SCT increasing to BKN or OVC, or changes from BKN or OVC decreasing to FEW or SCT.

(iii)

When no clouds of operational significance are forecast and ‘CAVOK’ is not appropriate, the abbreviation ‘NSC’ shall be used.

(5) Vertical visibility

When the sky is expected to remain or become obscured and vertical visibility observations are available at the aerodrome, and the vertical visibility is forecast to improve and change to or pass through one or more of the following values, or when the vertical visibility is forecast to deteriorate and pass through one or more of the following values: 100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m), the TREND forecast shall indicate the change.

(6) Additional criteria

The aerodrome meteorological office and the users may agree on additional criteria to be used, based on local aerodrome operating minima.

(7) Use of change groups

(i)

When a change is expected to occur, the TREND forecast shall begin with one of the change indicators ‘BECMG’ or ‘TEMPO’.

(ii)

The change indicator ‘BECMG’ shall be used to describe forecast changes where the meteorological conditions are expected to reach or pass through specified values at a regular or irregular rate. The period during which, or the time at which, the change is forecast to occur shall be indicated using the abbreviations ‘FM’, ‘TL’ or ‘AT’, as appropriate, each followed by a time group in hours and minutes.

(iii)

The change indicator ‘TEMPO’ shall be used to describe forecast temporary fluctuations in the meteorological conditions which reach or pass specified values and last for a period of less than 1 hour in each instance and, in the aggregate, cover less than one half of the period during which the fluctuations are forecast to occur. The period during which the temporary fluctuations are forecast to occur shall be indicated using the abbreviations ‘FM’ and/or ‘TL’, as appropriate, each followed by a time group in hours and minutes.

(8) Use of the probability indicator

The indicator ‘PROB’ shall not be used in TREND forecasts.

MET.TR.230 Forecasts for take-off

(a)

A forecast for take-off shall refer to a specified period of time and shall contain information on expected conditions over the runway complex in regard to surface wind direction and speed and any variations thereof, temperature, pressure, and any other elements as agreed between the aerodrome meteorological office and the operators.

(b)

The order of the elements and the terminology, units and scales used in forecasts for take-off shall be the same as those used in reports for the same aerodrome.

MET.TR.235 Aerodrome warnings and wind shear warnings and alerts

(a)

Wind shear warnings shall be issued in accordance with the template in Appendix 4.

(b)

The sequence number referred to in the template in Appendix 4 shall correspond to the number of wind shear warnings issued for the aerodrome since 00.01 UTC on the day concerned.

(c)

Wind shear alerts shall give concise, up-to-date information related to the observed existence of wind shear involving a headwind/tailwind change of 15 kt (7,5 m/s) or more which could adversely affect aircraft on the final approach path or initial take-off path and aircraft on the runway during the landing roll or take-off run.

(d)

Wind shear alert shall, if practicable, relate to specific sections of the runway and distances along the approach path or take-off path as agreed between the aerodrome meteorological office, the appropriate ATS units and the operators concerned.

Chapter 3 — Technical requirements for meteorological watch offices

MET.TR.250 SIGMET messages

(a)

The content and order of elements in a SIGMET message shall be in accordance with the template shown in Appendix 5.

(b)

SIGMET messages shall consist of three types:

(1)

SIGMET for en-route weather phenomena other than volcanic ash or tropical cyclones, referred as WS SIGMET;

(2)

SIGMET for volcanic ash, referred as WV SIGMET;

(3)

SIGMET for tropical cyclones, referred as WC SIGMET.

(c)

The sequence number of SIGMET messages shall consist of three characters comprising one letter and two numbers.

(d)

Only one of the phenomena listed in Appendix 5 shall be included in a SIGMET message, using the appropriate abbreviations and the following threshold value of surface wind speed of 34 kt (17 m/s) or more for tropical cyclone.

(e)

SIGMET information concerning thunderstorms or a tropical cyclone shall not include references to associated turbulence and icing.

(f)

SIGMET, if disseminated in digital form, shall be:

(1)

formatted in accordance with a globally interoperable information exchange model and shall use geography markup language (GML);

(2)

accompanied by the appropriate metadata.

MET.TR.255 AIRMET messages

(a)

The content and order of elements in an AIRMET message shall be in accordance with the template shown in Appendix 5.

(b)

The sequence number referred to in the template in Appendix 5 shall correspond to the number of AIRMET messages issued for the flight information region since 00.01 UTC on the day concerned.

(c)

Only one of the phenomena in Appendix 5 shall be included in an AIRMET message, using the appropriate abbreviations and the following threshold values, when the phenomena is below flight level 100, or below flight level 150 in mountainous areas, or higher, where necessary:

(1)

wind speed above 30 kt (15 m/s);

(2)

widespread areas affected by reduction of visibility to less than 5 000 m, including the weather phenomenon causing the reduction of visibility;

(3)

widespread areas of broken or overcast cloud with height of base less than 1 000 ft (300 m) above ground level.

(d)

AIRMET messages concerning thunderstorms or cumulonimbus clouds shall not include references to associated turbulence and icing.

MET.TR.260 Area forecasts for low-level flights

(a)

When chart form is used for area forecasts for low-level flights, the forecast of upper wind and upper-air temperature shall be issued for points separated by no more than 300 NM and for, as a minimum, the following altitudes: 2 000, 5 000 and 10 000 ft (600, 1 500 and 3 000 m) and 15 000 ft (4 500 m) in mountainous areas. The issuance of forecasts of upper wind and upper-air temperature at an altitude of 2 000 ft (600 m) may be subject to local orographic considerations as determined by the competent authority.

(b)

When chart form is used for area forecasts for low-level flights, the forecast of SIGWX phenomena shall be issued as low-level SIGWX forecast for flight levels up to 100, or up to flight level 150 in mountainous areas, or higher, where necessary. Low-level SIGWX forecasts shall include:

(1)

the following phenomena warranting the issuance of a SIGMET: icing, turbulence, cumulonimbus clouds that are obscured, frequent, embedded or occurring at a squall line, sandstorms/dust storms and volcanic eruptions or a release of radioactive materials into the atmosphere, and which are expected to affect low-level flights;

(2)

the following elements in area forecasts for low-level flights: surface wind, surface visibility, significant weather phenomena, mountain obscuration, cloud, icing, turbulence, mountain wave and height of zero-degree isotherm.

(c)

When the competent authority has determined that the density of traffic operating below flight level 100 warrants the issuance of an AIRMET message, the area forecasts shall be issued to cover the layer between the ground and flight level 100, or up to flight level 150 in mountainous areas, or higher, where necessary, and shall contain information on en-route weather phenomena hazardous to low-level flights, in support of the issuance of the AIRMET message and the additional information required for low-level flights.

Chapter 4 — Technical requirements for volcanic ash advisory centres (VAAC)

MET.TR.265 Volcanic ash advisory centre responsibilities

(a)

The advisory information on volcanic ash shall be issued in abbreviated plain language and in accordance with the template shown in Appendix 6. When no abbreviations are available, English plain language text, to be kept to a minimum, shall be used.

(b)

The volcanic ash advisory information, when prepared in graphical format, shall be as specified below

and shall be issued using:

(1)

the portable network graphics (PNG) format; or

(2)

the BUFR code form, when exchanged in binary format.

Chapter 5 — Technical requirements for tropical cyclone advisory centres (TCAC)

MET.TR.270 Tropical cyclone advisory centre responsibilities

(a)

The advisory information on tropical cyclones shall be issued for tropical cyclones when the maximum of the 10-minute mean surface wind speed is expected to reach or exceed 34 kt during the period covered by the advisory.

(b)

The advisory information on tropical cyclones shall be in accordance with Appendix 7.

Chapter 6 — Technical requirements for world area forecast centres (WAFCs)

MET.TR.275 World area forecast centre responsibilities

(a)

WAFCs shall use processed meteorological data in the form of grid point values expressed in binary form (GRIB code form) for the supply of gridded global forecasts and BUFR code form for the supply of forecast of significant weather phenomena.

(b)

For global gridded forecasts, WAFCs shall:

(1)

prepare forecasts of:

(i)

upper wind;

(ii)

upper-air temperature;

(iii)

humidity;

(iv)

direction, speed and flight level of maximum wind;

(v)

flight level and temperature of tropopause;

(vi)

areas of cumulonimbus clouds;

(vii)

icing;

(viii)

clear-air and in-cloud turbulence;

(ix)

geopotential altitude of flight levels;

four times a day and be valid for fixed valid times at 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and 36 hours after the time (00.00, 06.00, 12.00 and 18.00 UTC) of the synoptic data on which the forecasts were based;

(2)

issue forecasts in the order referred to in point (1) and complete their dissemination as soon as technically feasible, but not later than 6 hours after standard time of observation;

(3)

provide grid point forecasts in a regular grid with a horizontal resolution of 1,25° of latitude and longitude and comprising:

(i)

wind data for flight levels 50 (850 hPa), 100 (700 hPa), 140 (600 hPa), 180 (500 hPa), 240 (400 hPa), 270 (350 hPa), 300 (300 hPa), 320 (275 hPa), 340 (250 hPa), 360 (225 hPa), 390 (200 hPa), 410 (175 hPa), 450 (150 hPa) and 530 (100 hPa);

(ii)

temperature data for flight levels 50 (850 hPa), 100 (700 hPa), 140 (600 hPa), 180 (500 hPa), 240 (400 hPa), 270 (350 hPa), 300 (300 hPa), 320 (275 hPa), 340 (250 hPa), 360 (225 hPa), 390 (200 hPa), 410 (175 hPa), 450 (150 hPa) and 530 (100 hPa);

(iii)

humidity data for flight levels 50 (850 hPa), 100 (700 hPa), 140 (600 hPa) and 180 (500 hPa);

(iv)

horizontal extent and flight levels of base and top of cumulonimbus clouds;

(v)

icing for layers centred at flight levels 60 (800 hPa), 100 (700 hPa), 140 (600 hPa), 180 (500 hPa), 240 (400 hPa) and 300 (300 hPa);

(vi)

clear-air turbulence for layers centred at flight levels 240 (400 hPa), 270 (350 hPa), 300 (300 hPa), 340 (250 hPa), 390 (200 hPa) and 450 (150 hPa);

(vii)

in-cloud turbulence for layers centred at flight levels 100 (700 hPa), 140 (600 hPa), 180 (500 hPa), 240 (400 hPa) and 300 (300 hPa);

(viii)

geopotential altitude data for flight levels 50 (850 hPa), 100 (700 hPa), 140 (600 hPa), 180 (500 hPa), 240 (400 hPa), 270 (350 hPa), 300 (300 hPa), 320 (275 hPa), 340 (250 hPa), 360 (225 hPa), 390 (200 hPa), 410 (175 hPa), 450 (150 hPa) and 530 (100 hPa).

(c)

For global forecasts of en-route significant weather phenomena, WAFCs shall:

(1)

prepare SIGWX forecasts four times a day and shall be valid for fixed valid times at 24 hours after the time (00.00, 06.00, 12.00 and 18.00 UTC) of the synoptic data on which the forecasts were based. The dissemination of each forecast shall be completed as soon as technically feasible, but not later than 9 hours after standard time of observation;

(2)

issue SIGWX forecasts as high-level SIGWX forecasts for flight levels between 250 and 630;

(3)

include in SIGWX forecasts the following items:

(i)

tropical cyclone provided that the maximum of the 10-minute mean surface wind speed is expected to reach or exceed 34 kt (17 m/s);

(ii)

severe squall lines;

(iii)

moderate or severe turbulence (in cloud or clear air);

(iv)

moderate or severe icing;

(v)

widespread sandstorm/dust storm;

(vi)

cumulonimbus clouds associated with thunderstorms and with points (i) to (v);

(vii)

non-convective cloud areas associated with in-cloud moderate or severe turbulence and/or moderate or severe icing;

(viii)

flight level of tropopause;

(ix)

jet streams;

(x)

information on the location of volcanic eruptions that are producing ash clouds of significance to aircraft operations, comprising: volcanic eruption symbol at the location of the volcano and, in a separate text box on the chart, the volcanic eruption symbol, the name of the volcano, if known, and the latitude/longitude of the eruption. In addition, the legend of SIGWX charts should indicate ‘CHECK SIGMET, ADVISORIES FOR TC AND VA, AND ASHTAM AND NOTAM FOR VA’;

(xi)

information on the location of a release of radioactive materials into the atmosphere of significance to aircraft operations, comprising: the radioactive materials in the atmosphere symbol at the location of the release and, in a separate box on the chart, the radioactive materials in the atmosphere symbol, latitude/longitude of the site of the release and, if known, the name of the site of the radioactive source. In addition, the legend of SIGWX charts on which a release of radiation is indicated should contain ‘CHECK SIGMET AND NOTAM FOR RDOACT CLD’.

(4)

The following criteria shall be applied for SIGWX forecasts:

(i)

points (i) to (vi) of point (3) shall only be included if expected to occur between the lower and upper levels of the SIGWX forecast;

(ii)

the abbreviation ‘CB’ shall only be included when it refers to the occurrence or expected occurrence of cumulonimbus clouds:

(A)

affecting an area with a maximum spatial coverage of 50 % or more of the area concerned;

(B)

along a line with little or no space between individual clouds; or

(C)

embedded in cloud layers or concealed by haze;

(iii)

the inclusion of ‘CB’ shall be understood to include all weather phenomena normally associated with cumulonimbus clouds, i.e. thunderstorm, moderate or severe icing, moderate or severe turbulence, and hail;

(iv)

where a volcanic eruption or a release of radioactive materials into the atmosphere warrants the inclusion of the volcanic activity symbol or the radioactivity symbol in SIGWX forecasts, the symbols shall be included on SIGWX forecasts irrespective of the height to which the ash column or radioactive material is reported or expected to reach;

(v)

in the case of coincident or the partial overlapping of points (i), (x) and (xi) of point (3), the highest priority shall be given to point (x), followed by points (xi) and (i). The point with the highest priority shall be placed at the location of the event, and an arrow shall be used to link the location of the other point(s) to its (their) associated symbol(s) or text box(es).

(d)

Medium-level SIGWX forecasts for flight levels between 100 and 250 for limited geographical areas shall be issued.