The authority charged with the provision of the aeronautical meteorological service is the State Ltd “LATVIAN ENVIRONMENT, GEOLOGY AND METEOROLOGY CENTRE” (LEGMC). LEGMC is responsible for:

• provision of meteorological watch, area forecasts, SIGMET and AIRMET;

• provision of meteorological information to air traffic service units and search and rescue service units;

• provision of aerodrome forecasts and warnings;

• provision of consultation to flight crew members and other flight operations personnel.

Post:

Ltd. "Latvian Environment, Geology and Meteorology Centre"

Latgales iela 165

Rīga, LV-1019, Latvija

Tel: +371 67032600

Fax: NIL

Email: lvgmc@lvgmc.lv

AFS: EVRCYMYX

URL: https://videscentrs.lvgmc.lv

The State-joint Stock Company “Latvijas gaisa satiksme” is responsible at AD Riga, AD Lielvarde, AD Liepaja and AD Ventspils for:

• weather observing and reporting service;
• meteorological information distribution to the ARO Riga and flight planning rooms;
• meteorological information broadcasting service;
• provision of meteorological information to ATS units;
• provision of aerodrome climatological information.

Post:

State Joint-stock Company "Latvijas gaisa satiksme"

Meteorological Department

Muzeju iela 3, Lidosta “Rīga”

Mārupes pagasts, Mārupes novads, LV-1053, Latvija

Tel: +371 67300950

+371 67300970

Fax: +371 67300970

Email: lgs@lgs.lv

AFS: EVRRYFYX (COM Centre)

URL: https://www.lgs.lv

The meteorological services are provided in accordance with the requirements of Regulation (EU) No 2017/373, Annex V (Part-MET) and the provisions of ICAO Annex 3 “Meteorological service for International Air Navigation” that are adopted as additional provisions to complement this Regulation on matters left to EU Member States under this Regulation.

Differences from ICAO Annex 3 standards and recommended practices are listed in GEN 1.7.

Area meteorological watch is provided for the Riga FIR. The Forecasting Division of Forecasting and Climate Department of LEGMC, Riga, acts as the Meteorological Watch Office (MWO) for this area.

Table 1: GEN 3.5.3 Meteorological observations and reports

Name of station/ Location indicator	Type and frequency of observation/ automatic observing equipment	Types of MET reports and availability of a trend forecast	Observation System and Site(s)	Hours of operation	Climatological information
1	2	3	4	5	6
LIELVARDE/ EVGA	Half hourly AviMet	METAR MET REPORT SPECIAL SUPPLEMENTARY INFO METAR: recent weather, wind shear SUPPLEMENTARY INFO MET REPORT: recent weather, wind shear, MOD/SEV TURB or icing TREND in METAR/MET REPORT	SFC wind sensors: Two ultrasonic wind sensors (height 10 m): near TDZ RWY 18 (389 m from THR) and near TDZ RWY 36 (313 m from THR), 119 m west of the RWY CL. VIS/RVR equipment: Three forward-scatter meters: near the TDZ of RWY36 (313 m from THR), near the MID of RWY, near the TDZ of RWY 18 (389 m from THR) 100 m west of the RWY CL. Ceilometers: laser ceilometer at a lateral distance of 900 m to the south of THR of RWY 36 and laser ceilometer at a lateral distance of 905 m to the north of THR of RWY 18. Remote reading temperature, humidity and pressure sensors for TDZ RWY 18 and TDZ RWY36, located at a lateral distance119 m west of the RWY CL. Present weather sensor at the MID of RWY 100 m west of the RWY CL. Lightning detection sensor 40 m to the north from the MID of RWY and 120 m west from RWY CL.	H24	AVBL
LIEPAJA / EVLA	Half hourly AviMet	METAR/METAR AUTO MET REPORT/MET REPORT AUTO SPECIAL/SPECIAL AUTO SUPPLEMENTARY INFO NIL	SFC wind sensors: ultrasonic wind sensors (height 10 m) near TDZ of RWY 24 (390 m from THR) and near TDZ of RWY 06 (295 m from THR) 190 m north of the RWY CL. Visibility/RVR equipment: forward-scatter meters: near TDZ of RWY 06 (295 m from THR) and near TDZ of RWY 24 (340 m from THR) 90 m north of the RWY CL. Ceilometers: one laser ceilometer at a lateral distance of 830 m to the south-west of THR of RWY 06 and one laser ceilometer at a lateral distance of 410 m to the north-east of THR of RWY 24. Remote reading temperature, humidity and pressure sensors near TDZ RWY 24 and TDZ RWY 06, 190 m north of the RWY centerline. Digital barometric pressure system at the TWR building. Present weather sensor near TDZ of RWY 24 m, 90 m north of the RWY centerline. Lightning detection sensor near TDZ of RWY 06, 190 m north of the RWY centerline.	H24	AVBL
RIGA/ EVRA	Half hourly MIDAS IV	METAR MET REPORT SPECIAL SUPPLEMENTARY INFO TREND	SFC wind sensors: two main ultrasonic wind sensors (height 10 m) for TDZ RWY 36 and two back-up ultrasonic wind sensors (height 10 m) for TDZ RWY 18, located at a lateral distance 128 m west of the RWY CL. VIS/RVR equipment: three main forward-scatter meters: near the TDZ of RWY 36 (380 m from THR), near the MID of RWY, near the TDZ of RWY 18 (370 m from THR) 80 m west of the RWY CL. Three back-up forward-scatter meters: near the TDZ of RWY 36 (380 m from THR), near the MID of RWY, near the TDZ of RWY 18 (370 m from THR) 90 m west of the RWY CL. Ceilometers: two laser ceilometers at a lateral distance of 920 m to the south of THR of RWY 36 and two laser ceilometers at a lateral distance of 1135 m to the north of THR of RWY 18. Remote reading temperature, humidity and pressure sensors (main and back-up) for TDZ RWY 18 and TDZ RWY 36, located at a lateral distance 128 m west of the RWY CL. One digital barometric pressure system at the TWR building. Main and back-up present weather sensors at the MID ofRWY 80 m and 90 m west of the RWY CL. Lightning detection sensor 430 m to the north from THR RWY 18 and 164 m west from RWY CL.	H24	AVBL
VENTSPILS/ EVVA	Half hourly Aviation Weather reporter	METAR AUTO SUPPLEMENTARY INFO NIL	A stand-alone weather observation system AW11, including wind sensors, visibility sensor, ceilometer, rain detector (weather phenomena - RA, DZ, SN, FG, BR, HZ), air temperature and humidity sensors, pressure sensor. AW11 is located at a lateral distance of 204 m from the runway centre and 340 m from the threshold of RWY 21.	H24	AVBL

NOTES:

Reports of surface weather observations consist of:

Routine reports:

AD Riga

• half-hourly report (H+20 and H+50) in METAR/MET REPORT forms;

AD Lielvarde

• half-hourly report (H+20 and H+50) in METAR/MET REPORT forms;

AD Liepaja

• half-hourly reports (H+20 and H+50) in METAR/MET REPORT forms (during AFIS operational hours only when funnel cloud, low drifting snow, blowing snow, squall, hail, shallow fog, partial fog and/or CB and/or TCU clouds occur at the aerodrome);
• half-hourly reports (H+20 and H+50) in METAR AUTO/MET REPORT AUTO forms (in all other cases except mentioned above);

AD Ventspils

• half-hourly report (H+20 and H+50) in METAR AUTO form.

METAR and METAR AUTO are disseminated beyond the aerodrome of origin via the AFTN/AMHS channel. METAR for AD Riga are included in VOLMET broadcast/D-VOLMET.

Special reports:

Special observations (between the routine observations) are made whenever changes in criteria specified in ICAO Annex 3, Appendix 3, paragraphs 2.3.2 and 2.3.3 occur (see Table below). Special reports are issued immediately after an observation and are not disseminated beyond the aerodromes of origin. Results of special observation at aerodromes are made available for Riga FIR users:

• AD Riga - via ATIS broadcasts/D-ATIS and ATS units;
• AD Lielvarde – via ATIS broadcasts and ATS units;
• AD Liepaja - via AFIS unit;
• AD Ventspils - via METEO INF broadcasts (H24)*.

Note: * observations are made without human intervention.

Special reports will be issued when one or more of the following criteria occur:

Weather element	EVRA AD	EVLA AD	EVGA AD	EVVA AD
Surface wind - the mean wind direction has changed by 60º or more from that given in the latest report, if the mean speed before and/or after the change is 10 kt or more; - the mean wind speed has changed by 10 kt or more from that given in the latest report; - the variation from the mean surface wind speed (gusts) has increased by 10 kt or more from that given in the latest report, the mean speed before and/or after the change being 15 kt or more.	X	X	X	X
Visibility - the visibility, in case of deterioration, passes through one or more of the following values 800 m, 1500 m, 3000 m (see note 1, 2), 5000 m or, in case of improvement, changes to or passes through one or more of the above values.	X	X	X	X
Runway Visual Range (RVR) - the RVR, in case of deterioration, passes through one or more of the following values: 175 m, 300 m, 400 m (see note 6), 550 m, 800 m or, in case of improvement, changes to or passes through one or more of the above values.	X	X	X	-
Present weather (see note 3, 4, 5) - when the onset, cessation or change in intensity of any of the following weather phenomena occurs: freezing precipitation; moderate or heavy precipitation (including showers thereof); thunderstorm (with precipitation); funnel cloud (tornado or waterspout); - when the onset or cessation of any of the following weather phenomena occurs: freezing fog; thunderstorm (without precipitation), low drifting snow; blowing snow; squall.	X	X	X	X
Cloud - the height of the base of the lowest cloud layer with 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: 100 ft, 200 ft, 500 ft, 1000 ft, 1500 ft; - the amount of a cloud layer below 1500 ft changes: from SCT or less to BKN or OVC or from BKN or OVC to SCT or less.	X	X	X	X
Vertical visibility - 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 ft, 200 ft, 500 ft, 1000 ft.	X	X	X	X
Temperature - an increase in air temperature of 2°C or more from that given in the latest local report.	X	X	X	-
Atmospheric pressure (QNH) - QNH value has changed by 2 hPa or more from that given in the latest report.	X	X	X	-
1. Not applicable for AD RIGA and AD LIELVARDE. Criteria for visibility, such as 800 m and 5000 m are not used for AD RIGA ATIS broadcast/D-ATIS and AD LIELVARDE ATIS broadcast update. 2. Not applicable for AD LIEPAJA. 3. Issued at AD VENTSPILS in automated mode when the onset or cessation or change in intensity of moderate or heavy precipitation occurs. 4. The criteria: when the onset or cessation or change in intensity of sandstorm or duststorm occurs; when the onset or cessation of low drifting sand or dust and blowing sand or dust occurs, are not used and listed in the table due to meteorological conditions. 5. The criteria: when the onset, cessation or change in intensity of hail, low drifting snow, blowing snow, squall, funnel cloud occurs, at AD LIEPAJA is used during AFIS operational hours only. 6. RVR criteria 400 m is used only at AD LIELVARDE.

OBSERVING SYSTEM AND OPERATING PROCEDURES

At all aerodromes, automated weather observing systems (AWOS) are installed. Human meteorological observations (by certified observers) (visibility, cloud type and/or amount, present weather) are made in addition to automated observations at AD Riga (H24) and AD Lielvarde (H24). At AD Liepaja human meteorological observations are made only during AFIS operational hours when hail, shallow fog, partial fog, funnel cloud, low drifting snow, blowing snow, squall; and/or CB and/or TCU clouds are observed at the aerodrome. The AWOS at AD Ventspils (H24) and AD Liepaja (except when there is weather phenomena and/or clouds above are observed at the aerodrome and its vicinity) produce and disseminate weather observation results in the form of METAR AUTO which are prepared in fully automated mode without human intervention.

1. AD RIGA

At Riga aerodrome, the MIDAS IV automated weather observing system is installed. The MIDAS IV conforms to the applicable Regulation (EU) No 2017/373 regulation (Part MET), ICAO and WMO requirements, supporting all relevant measurements in aviation meteorology. Additionally, a certified observer provides observations on weather phenomena, cloud type and cloud amount at the aerodrome and its vicinity. If main and back-up visibility sensors installed near the TDZ of the runway-in-use fail simultaneously, visual visibility observations (if necessary) are made by a certified observer.

Surface wind. Surface wind direction and speed are measured by ultrasonic wind sensors located near both ends of the runway at a lateral distance of 128 m from the runway centreline and at a height of 10 m above the ground surface. See Table GEN 3.5.3 for detailed information. The unit knot (KT) is used to indicate surface wind speed. The true wind direction, wind speed, variation in wind direction (consisting of the two extreme directions between which the wind has varied) and variation from the mean wind speed (gust) with a 10-minute average are reported in METAR. The wind data from the wind sensor installed near RWY 36 is always included in the current METAR. The magnetic wind direction and speed (2-minute average), and variations from the mean wind speed (gusts) (during the previous 10 minutes) from the wind sensor installed near the runway-in-use are reported via ATIS broadcasts/D-ATIS. All real-time wind data, including the runway crosswind and headwind components, from both wind sensors are available in local ATS units.

Visibility. Visibility for aeronautical purposes (as defined in ICAO Annex 3) is measured or observed visually by a human observer (if necessary) and reported in metres or kilometres. Reported visibility in METAR is the prevailing visibility value (10-minute average). The prevailing visibility is the visibility value which is reached or exceeded within at least half the horizon circle or within at least half of the surface of the aerodrome. When the visibility is not the same in different directions and the lowest visibility is different from the prevailing visibility, and 1) less than 1500 m or 2) less than 50% of the prevailing visibility and less than 5000 m, the lowest visibility is also included in METAR (without indication of its general direction). In Special reports (disseminated within the aerodrome only) and ATIS broadcasts/D-ATIS, the visibility value (1-minute average) for the touchdown zone of the runway-in-use is reported. The visibility is measured instrumentally by means of forward-scatter meters at a height of approximately 2.5 m above the runway level. In all reports, the visibility value is reported in steps of 50m when the visibility is less than 800 m; in steps of 100 m when it is 800 m or more but less than 5km; in steps of 1000m when it is 5000m or more but less than 10 km; and is given as 10 km when it is 10 km or above. All values are updated in 15-second intervals. When the visibility is improving or deteriorating and changes to or passes through 1500 m, this value will be included in the updated ATIS broadcasts/D-ATIS. ATS units have visibility data (1-minute average) for the: touchdown zone, mid-point and stop-end of the runway.

Runway Visual Range. Assessment of the runway visual range (RVR) is carried out by means of forward-scatter meters. For the location of forward-scatter meters along the runway, see Table GEN 3.5.3 and EVRA AD 2.24.1.The RVR assessments by forward-scatter meters are made by using 100% runway light intensity for all reports. The RVR is reported in metres throughout periods when either the visibility or the RVR is less than 1500 m. The lower limit for RVR reporting is 50 m and 2000 m is the upper limit. The RVR is reported in steps of 25 m for RVR up to 400 m, in steps of 50 m for the RVR from 400 m to 800 m and in steps of 100 m for RVR above 800 m (till 2000 m). All values are updated at 15-second intervals. The RVR value (10-minute average) representative of the touchdown zone for the runway-in-use is included in the current METAR. The RVR values (1-minute average) from three locations along the runway (touchdown zone of the runway-in-use, midpoint and stop-end) are included in the current ATIS broadcast/D-ATIS. ATS units have the real RVR data (1-minute average) for three locations along the runway: touchdown zone, mid-point and stop-end. When the RVR value which is representative of the touchdown zone of the runway-in-use is improving and changes to or passes through one or more of the following values, or when the RVR value is deteriorating and passes through one or more of the following values: 175 m, 300 m, 550 m, 800 m, those values will be included in the updated ATIS broadcast/D-ATIS.

Present weather. The present weather phenomena are observed by means of a present weather sensor, lightning detection sensor and, additionally, by a certified observer. For the location of the sensors, see Table GEN 3.5.3. Present weather phenomena are reported in accordance with Regulation (EU) No 2017/373 (Part MET), ICAO Annex 3 Appendix 3 paragraph 4.4 and WMO-No.-306 “Manual on Codes” Code table 4678 requirements.

Clouds. The diode laser LIDAR ceilometers are used at the aerodrome to determine the height of the cloud base and amount of cloud. For the location of ceilometers, see Table GEN 3.5.3. The height of cloud base is reported in feet above the aerodrome elevation. The height of cloud base is reported in steps of 50 ft up to and including 300 ft and in steps of 100 ft up to 10000 ft and in steps of 1000 ft above 10000 ft. The measurements range is up to 25000 ft. The ICAO algorithm is used for cloud base calculations. Only cloud of operational significance (a cloud with the height of cloud base below 5000 ft or a CB or a TCU at any height) is included in all reports and ATIS broadcasts/D-ATIS. ATS units have the data on the height of cloud base, cloud amount and type of clouds (CB and TCU respectively), or the data on the vertical visibility (if necessary). When the height of the base of the lowest cloud layer of BKN or OVC extent is lifting and changes to or passes through, or when the height of the base of the lowest cloud layer of BKN or OVC extent is lowering and passes through: 100 ft, 200 ft, 500 ft, 1000 ft or 1500 ft, those values will be included in the updated ATIS broadcast/D-ATIS. When the sky is obscured and the vertical visibility is improving or deteriorating and changes to or passes through: 100 ft, 200 ft, 500 ft, 1000 ft, those values will be included in the updated ATIS broadcasts/D-ATIS too.

Temperature/dew point. The humidity and temperature probes (main and back-up MAWS sensors) are used for measuring the relative humidity (from which the dew point temperature is calculated) and air temperature. Air temperature and dew point temperature data is representative of the runway and is reported in steps of whole degrees Celsius. For the location of the sensors, see Table GEN 3.5.3. Air temperature and dew point temperature are included in ATIS broadcasts/D-ATIS. ATS units have the air and dew point temperature data. All values are updated at 60-second intervals.

Atmospheric pressure. Digital aviation barometers are used (main and back-up MAWS sensors) for QNH and QFE value calculations. All values are updated at 60-second intervals. For the location of the sensors, see Table GEN 3.5.3. The QNH value in steps of whole hectopascals is included in all reports and ATIS broadcast/D-ATIS. If required by the pilot, the QFE value in whole hectopascals for the THR of RWY 36 or the THR of RWY 18 (whichever is necessary), is reported via the ATS units. The QNH value in inches of mercury (in Hg), rounded down to the nearest 0.01 in Hg, is also made available to pilots via the ATS units.

b. AD LIELVARDE

At Lielvarde aerodrome, the AviMet automated weather observing system is installed. The AviMet conforms to the applicable Regulation (EU) No 2017/373 (Part MET), ICAO and WMO requirements, supporting all relevant measurements in aviation meteorology. Additionally, a certified observer provides observations on weather phenomena, cloud type and cloud amount at the aerodrome and its vicinity. If a visibility sensor installed near the TDZ of the runway-in-use fails, visual visibility observations (if necessary) are made .

Surface wind. Surface wind direction and speed are measured by ultrasonic wind sensors located near both ends of the runway at a lateral distance of 119 m from the runway centerline and at a height of 10 m above the ground surface. See Table GEN 3.5.3 for detailed information. The unit knot (KT) is used to indicate the surface wind speed. The true wind direction, wind speed, variation in wind direction (consisting of the two extreme directions between which the wind has varied) and variation from the mean wind speed (gust) with a 10-minute average are reported in METAR. The wind data from the wind sensor installed near RWY 36 is always included in the current METAR. The magnetic wind direction and speed (2-minute average), and variations from the mean wind speed (gusts) (during the previous 10 minutes) from the wind sensor installed near the runway-in-use are reported via ATIS broadcast. All real-time wind data, including the runway crosswind and headwind components, from both wind sensors are available in ATS units.

Visibility. Visibility for aeronautical purposes (as defined in EU Reg. 2017/373 and ICAO Annex 3) is measured or observed visually by a human observer (if necessary) and reported in meters or kilometers. Reported visibility in METAR is the prevailing visibility value (10-minute average). The prevailing visibility is the visibility value which is reached or exceeded within at least half the horizon circle or within at least half of the surface of the aerodrome. When the visibility is not the same in different directions and the lowest visibility is different from the prevailing visibility, and 1) less than 1500 m or 2) less than 50% of the prevailing visibility and less than 5000 m, the lowest visibility is also included in METAR. In Special reports (disseminated within the aerodrome only) and ATIS broadcasts, the visibility value (1-minute average) for the touchdown zone of the runway-in-use is reported. The visibility is measured instrumentally by means of forward-scatter meters at a height of approximately 2.5 m above the runway level. In all reports, the visibility value is 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 steps of 1000 m when it is 5000 m or more but less than 10 km; and is given as 10 km when it is 10 km or above. All values are updated in 15-second intervals. When the visibility is improving or deteriorating and changes to or passes through 800 m, 1500 m, 3000 m and 5000 m, this value will be included in the updated ATIS broadcast. ATS units hasve visibility data (1-minute average) for the: touchdown zone, mid-point and stop-end of the runway.

Runway Visual Range. Assessment of the runway visual range (RVR) is carried out by means of forward-scatter meters. For the location of forward-scatter meters along the runway, see Table GEN 3.5.3 and EVGA AD 2.24.1-1.The RVR assessments by forward-scatter meters are made by using 100% runway light intensity for METAR reports. For local routine and local special reports, and also for real RVR data (for ATS units), RVR assessments are made by using the runway light intensity that is actually in use on the runway (if the light intensity is more than 3%), or by using the optimum light intensity (if the light intensity is 3% or less, or if the runway lights are switched off).The RVR is reported in meters throughout periods when either the visibility or the RVR is less than 1500 m. The lower limit for RVR reporting is 50 m and 2000 m is the upper limit. The RVR is reported in steps of 25 m for RVR up to 400 m, in steps of 50 m for the RVR from 400 m to 800 m and in steps of 100 m for RVR above 800 m (till 2000 m). All values are updated at 15-second intervals. The RVR value (10-minute average) representative of the touchdown zone for the runway-in-use is included in the current METAR. The RVR values (1-minute average) from three locations along the runway (touchdown zone of the runway-in-use, midpoint and stop-end) are included in the current ATIS broadcast. ATS units hasve the real RVR data (1-minute average) for three locations along the runway: touchdown zone, mid-point and stop-end.

Present weather. The present weather phenomena are observed by means of a present weather sensor, lightning detection sensor and, additionally, by the observer. For the location of the sensors, see Table GEN 3.5.3. Present weather phenomena are reported in accordance with Regulation (EU) No 2017/373 (Part MET), ICAO Annex 3 Appendix 3 paragraph 4.4 and WMO-No.-306 “Manual on Codes” Code table 4678 requirements.

Clouds. The diode laser LIDAR ceilometers are used at the aerodrome to determine the height of the cloud base and amount of cloud. For the location of ceilometers, see Table GEN 3.5.3. The height of cloud base is reported in feet above the aerodrome elevation. The height of cloud base is reported in steps of 50 ft up to and including 300 ft and in steps of 100 ft up to 10000 ft and in steps of 1000 ft above 10000 ft. The measurements range is up to 25000 ft. The ICAO algorithm is used for cloud base calculations. Only the cloud of operational significance (a cloud with the height of cloud base below 5000 ft or a CB or a TCU at any height) is included in all reports and ATIS broadcast. ATS units hasve the data on the height of cloud base, cloud amount and type of clouds (CB and TCU respectively), or the data on the vertical visibility (if necessary). When the height of the base of the lowest cloud layer of BKN or OVC extent is lifting and changes to or passes through, or when the height of the base of the lowest cloud layer of BKN or OVC extent is lowering and passes through: 100 ft, 200 ft, 500 ft, 1000 ft or 1500 ft, those values will be included in the updated ATIS broadcast. When the sky is obscured and the vertical visibility is improving or deteriorating and changes to or passes through: 100 ft, 200 ft, 500 ft, 1000 ft, those values will be included in the updated ATIS broadcast too.

Temperature/dew point. The humidity and temperature probes are used for measuring the relative humidity (from which the dew point temperature is calculated) and air temperature. Air temperature and dew point temperature data is representative of the runway and is reported in steps of whole degrees Celsius. For the location of the sensors, see Table GEN 3.5.3. Air temperature and dew point temperature are included in ATIS broadcast. ATS units hasve the air and dew point temperature data. All values are updated at 60-second intervals.

Atmospheric pressure. Digital aviation barometers are used for QNH and QFE value calculations. All values are updated at 60-second intervals. For the location of the sensors, see Table GEN 3.5.3. The QNH value in steps of whole hectopascals is included in all reports and ATIS broadcast. If required by the pilot, the QFE value in whole hectopascals is reported via the ATS units. The QNH value in inches of mercury (in Hg), rounded down to the nearest 0.01 in Hg, is also made available to pilots via the ATS units.

c. AD LIEPAJA

At AD Liepaja, the AviMet automated weather observing system is installed. The AviMet conforms to the applicable Regulation (EU) No 2017/373 (Part MET), ICAO and WMO requirements, supporting all relevant measurements in aviation meteorology. The system is operated in fully automated mode without human intervention (the automated observation during AFIS operational hours is supported by a certified observer only when,hail, shallow fog, partial fog, funnel cloud, low drifting snow, blowing snow, squall; or CB and/or TCU clouds occur at the aerodrome). For the location of sensors, see Table GEN 3.5.3.

Surface wind. Surface wind is measured by ultrasonic wind sensors located near both ends of the runway at a lateral distance of 190 m from the runway centre line. These wind sensors are installed at a height of 10 m above the ground surface. The unit knot (kt) is used to indicate the surface wind speed. The true wind direction, wind speed, variation in wind direction (consisting of the two extreme directions between which the wind has varied) and variation from the mean wind speed (gusts) during the past 10 minutes, measured by the wind sensor installed near RWY 24, are always reported in METAR/METAR AUTO.

AFIS unit has a real-time weather display with all wind data, including magnetic wind direction and speed (2-minute average), variation from the mean wind speed (gusts) during the past 10 minutes, minimum and maximum wind speed values (2-minute average), crosswind, tailwind and headwind values, from both sensors installed near the runway (RWY06/24). All values are updated at 3-second intervals.

Visibility. Visibility for aeronautical purposes (as defined in ICAO Annex 3) is measured instrumentally by means of forward-scatter meters at a height of approximately 2.5 m above the runway level. In all reports the visibility value is 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 steps of 1000 m when it is 5000 m or more but less than 10 km; and is given as 10 km when it is 10 km or above. Reported visibility in METAR/METAR AUTO is the prevailing visibility value (10-minute average). In accordance with the algorithm recommended by ICAO for an automatic system with two visibility sensors (ICAO Doc 9837 paragraph 4.3.3.4, Table 4-1), the lowest visibility observed is taken as the prevailing visibility. When the visibility is not the same in different directions, criteria for additional reporting of the lowest visibility and its general direction (Annex 3, Appendix 3, 4.2.4.4 a)) are not applicable (the reported prevailing visibility equals the lowest visibility). In MET REPORT/MET REPORT AUTO and SPECIAL/SPECIAL AUTO reports (disseminated within the aerodrome only), the visibility value (1-minute average) representative of the touchdown zone of the runway-in-use is reported. All values are updated at 15-second intervals. The AFIS unit has a real time visibility data (1-minute average, updated at 15-second intervals) for the: touchdown zone and stop-end of the runway. Visual observations are not made when forward-scatter meter(s) fail.

Runway Visual Range. Assessment of the runway visual range (RVR) is carried out by means of forward-scatter meters only. For the location of forward-scatter meters along the runway, see Table GEN 3.5.3. RVR assessments by forward-scatter meters are made by using 100% runway light intensity for all reports. The RVR is reported in metres throughout periods when either the visibility or the RVR is less than 1500 m. The lower limit for RVR reporting is 50 m and 2000 m is the upper limit. The RVR is reported in steps of 25 m for RVR up to 400 m, in steps of 50 m for RVR from 400 m up to 800 m and in steps of 100 m for RVR above 800 m (till 2000 m). All values are updated at 15-second intervals. The RVR values (10-minute average) for both touchdown zones of the runway are included in the current METAR/METAR AUTO. The AFIS unit has real RVR data (1-minute average, updated at 15-second intervals) for the touchdown zone and stop-end of the runway. When the RVR value which is representative of the touchdown zone for the runway-in-use improves and changes to or passes through: 175 m, 300 m, 550 m and 800 m, those values are used as criteria for issuing SPECIAL reports.

Present weather. The present weather phenomena are observed by means of present weather sensor and lightning detection sensor only, except when during AFIS operational hours the automated observation is supported by a certified observer when hail, shallow fog, partial fog, funnel cloud, low drifting snow, blowing snow, squall; and/or CB and/or TCU clouds are observed at the aerodrome). Present weather phenomena are reported in accordance with Regulation (EU) No 2017/373 (Part MET), ICAO Annex 3 Appendix 3 paragraph 4.4 requirements. The following weather phenomena or combination thereof are not reported in the automated reports (METAR AUTO, MET REPORT AUTO and Special AUTO): GR, GS, SA, VA, PO, SQ, FC, DS, SS, SNRA , MIFG, PRFG, VCSH, VCFG.

Clouds. Diode laser LIDAR ceilometers are used at the aerodrome to determine the height of the cloud base and the amount of cloud. For the location of ceilometers, see Table GEN 3.5.3. The height of the cloud base is reported in ft above the aerodrome elevation. The height of cloud base is reported in steps of 100 ft up to 10000 ft and in steps of 1000 ft above 10000 ft. The measurements range is up to 25000 ft. The ICAO algorithm is used for cloud base calculations. Only cloud of operational significance (a cloud with the height of cloud base below 5000 ft) is included in all reports. All values are updated at 30-second intervals. Cloud type CB and/or TCU is available for all reports only during AFIS operational hours when the automated observation is supported by certified observer. In all automated reports cloud type is not included (except when the TS is observed in automated report – then CB will be also reported). The AFIS unit has real-time cloud data, including the height of the cloud base, the amount of cloud and cloud type.

Temperature/dew point. The humidity and temperature probes are used for measuring the relative humidity (from which the dew point temperature is calculated) and air temperature. Air temperature and dew point temperature data is representative of the runway and is reported in steps of whole degrees Celsius. For the location of the sensors, see Table GEN 3.5.3. AFIS unit has the air and dew point temperature data. All values are updated at 60-second intervals.

Atmospheric pressure. Digital aviation barometers are used as main and backup sensors for QNH and QFE value calculations. All values are updated at 60-second intervals. For the location of the sensors, see Table GEN 3.5.3. The QNH value in steps of whole hectopascals is included in all automated reports. If required by the pilot, the QFE value in whole hectopascals for the THR of RWY 24 or the THR of RWY 06 (whichever is necessary), can be reported by the AFIS unit. The QNH value in inches of mercury (in Hg), rounded down to the nearest 0.01 in Hg is also available via the AFIS unit.

d. AD VENTSPILS

Weather observations at AD Ventspils for METAR AUTO and METEO INF broadcast on channel 126.805 (8.33 channel) (for non-8.33 kHz equipped State aircraft broadcast on frequency 126.800 MHz) are carried out by the stand-alone automated weather observing system, AW11, including wind sensors, visibility sensor, ceilometer, rain detector (detecting weather phenomena - rain, drizzle, snow, fog, mist, haze), air temperature and humidity sensors and a pressure sensor. For the location of AW11, see Table GEN 3.5.3.

The total height of the AW11 (including VHF antenna and lightning rod) is 8 m above the ground surface.

Surface wind. Surface wind is measured by anemometer and wind wane. These wind sensors are installed at a height of 6 m above the ground surface. The unit knot (kt) is used to indicate surface wind speed. The true wind direction, wind speed, variation in wind direction (consisting of the two extreme directions between which the wind has varied) and variation from the mean wind speed (gusts) during the past 10 minutes are reported in METAR AUTO. The true wind direction and speed (2-minute average), and gusts (during the past 10 minutes) from the system AW11’s wind sensors is always included in METEO INF broadcasts.

Visibility. Visibility for aeronautical purposes (as defined in ICAO Annex 3) is measured using the forward-scatter meter at a height of approximately 2.5 m above the ground surface and reported in metres or kilometres. In all automated reports (METAR AUTO, Special and METEO INF broadcasts), the visibility value is reported which is derived from the point of measurement without directional variations measurements.

Runway Visual Range. Assessment of runway visual range (RVR) is not carried out.

Present weather. The present weather phenomena are observed by means of a rain detector sensor only. Present weather phenomena (FG, PRFG, BR, HZ, -RA, RA, +RA, RASN, -SN, SN, +SN, SNRA, DZ) are reported in accordance with ICAO Annex 3 Appendix 3 paragraph 4.4.2.3 requirements. The following weather phenomena or combination thereof are not reported in the automated reports (METAR AUTO, Special and METEO INF): TS, SG, PL, GR, GS, SA, DU, FU, VA, PO, SQ, FC, DS, SS, MIFG, FZFG, FZRA, FZDZ, BCFG, VCTS, VCSH, VCFG.

Clouds. Cloud observations are made near one of the touchdown zones of the runway (for details, see Table GEN 3.5.3). The height of cloud base is reported in ft above the aerodrome elevation. The height of cloud base is reported in steps of 100 ft. The measurement range is up to 6400 ft. The ICAO algorithm is used for cloud base calculations. Cloud type is not included in all reports.

Temperature/dew point. Air temperature and relative humidity (from which the value of the dew point temperature is calculated) are measured using a Humidity and Temperature Probe. Air temperature and humidity sensors are installed at a height of approximately of 2 m above the ground surface.

Notes:

1. The observations AD Ventspils (H24) and AD Liepaja (H24, except when the automated observation is supported by a certified observer during AFIS operational hours) are provided without human intervention using AWOS in fully automated mode. When automatic weather reports are transmitted via AFS, those messages contain the type indicator AUTO (METAR AUTO).

2. Only the visibility value for the measurement point (for details, see Table GEN 3.5.3 ) is included in automated reports and METEO INF broadcasts for AD Ventspils. In automated reports which are transmitted via METEO INF broadcasts, the visibility value has a 10-minute averaging period. The directional variation of visibility is not included in all automated reports.

3. Due to technical limitations, the AWOS at AD Ventspils (H24) is not able to observe all freezing conditions or thunder. Freezing conditions or thunder may exist at aerodrome even if not included in METAR AUTO and other automated reports. These conditions are not included in METEO INF broadcasts which are always based on automated observation reports at AD Ventspils. The system at Ventspils aerodrome is able to detect rain, drizzle, snow, fog, mist and haze only.

4. Due to technical limitations, the AWOS are not able to observe CB and/or TCU clouds. CB and/or TCU clouds may exist at aerodromes even if not included in METAR AUTO respectively METEO INF (AD Ventspils) (H24) broadcasts. The systems are not able to observe cloud amount as accurately as a human observer.

5. Due to software features, the AW11 reports CAVOK conditions when there are CB and/or TCU clouds at a height above 5000 ft and/or a weather phenomenon that cannot be detected by the AW11 system exist at AD Ventspils. Due to software features, the “AviMet” system reports NSC conditions when there are CB and/or TCU clouds at a height above 5000 ft at AD Liepaja (except when the automated observation is supported by a certified observer during AFIS operational hours).

e. Supplementary information

Information on the existence of wind shear along the take-off path or approach path between the runway level and 1600 ft based on pilot reports via ATS units at AD Riga and AD Lielvarde is always included in METAR and ATIS broadcasts/D-ATIS. Information on the existence of wind shear is one of the criteria for the issue of local special reports and regular ATIS broadcast/D-ATIS updates. Information on the existence of wind shear is cancelled for all reports after the elapsed time period of 30 minutes.

Note: D-ATIS only for AD Riga.

Wind shear information is not included in METAR/METAR AUTO for AD Liepaja nor METAR AUTO for AD Ventspils.

• MET information for pre-flight planning

The meteorological office designated for providing meteorological forecast services to civil aviation in Latvia is the Forecasting Division of Forecasting and Climate Department of LEGMC, Riga, which operates H24.

MET briefings and flight documentation are provided on request by the ARO Riga and at the flight planning rooms at AD Liepaja and AD Ventspils, as indicated in the respective AD parts.

LGS automated pre-flight information system (Internet self-briefing - IBS) provides a harmonized, common point of access to meteorological information and aeronautical information for operators, flight crew members and other aeronautical personnel. IBS provides integrated NOTAM, SNOWTAM and MET briefings (including Weather Charts and Narrow Route briefings), and incorporates facilities for filing of flight plans. PIB and additional AIS/MET information are available on: https://ibs.lgs.lv and from ARO Riga. Meteorological information is available without registration.

Flight documentation is provided for international and domestic flights and comprises an appropriate fixed time significant weather chart (SWL, SWM/SWH for all ICAO regions, if necessary), fixed time upper wind/upper air temperature prognostic charts (for all ICAO regions, if necessary), GAMET area forecasts, SIGMET and AIRMET messages, and the latest available TAF and METAR/SPECI for the departure, destination and alternate aerodromes.

Aerodrome reports, including trend forecasts and TAFs for the Latvian aerodromes, are issued as listed in Table GEN 3.5.3 and the respective AD part. Forecasts for take-off in respect of surface wind, temperature, QNH and any other elements expected over the runway at AD Riga, AD Lielvarde and AD Liepaja can be prepared by the Forecasting Division of Forecasting and Climate Department of LEGMC. The forecast is supplied on request within 3 hours prior to the expected time of departure. The request should be made to a forecaster by telephone +371 67142005.

A personal consultation by a forecaster can be obtained from the Forecasting Division of Forecasting and Climate Department of LEGMC by telephone only (see AD parts). In order to provide an effective and complete consultation, a prior request should be made to a forecaster at least half an hour before the time at which the consultation is required.

Also, the weather satellite picture covering the EUR region is available using the appropriate link from website http://ibs.lgs.lv. Information is updated every 15 minutes.

Some specific types of meteorological information, such as thermal activity and temperature inversion forecasts, can be supplied to air-sports users (glider, microlight and hot air balloon organisations) by prior arrangement with LEGMC only. Enquiries should be made to LEGMC (see GEN 3.5.1). Weather information for these flight operations which is available within the framework of routine forecast preparation, can be obtained by a pilot in the form of a consultation with an aviation forecaster (tel: +371 67142005).

Information obtained from ground-based meteorological radar (Doppler type) installed near AD Riga is also available using the appropriate link from website http://ibs.lgs.lv.

Information about space weather is available on request only in ARO Riga.

• MET information for general aviation flights

Meteorological information for general aviation flights departing from AD Riga, AD Lielvarde, AD Liepaja and AD Ventspils is supplied, as described above in previous paragraph. In other cases, meteorological information for pre-flight planning can be obtained directly from an aviation forecaster by telephone +371 67142005.

Area forecasts for low-level flights operating below FL100, including under VFR, are issued by the Forecasting Division of Forecasting and Climate Department of LEGMC. These forecasts are supplied in chart form (ICAO Annex 3, Model SWL, example 1) and as a GAMET area forecast for the Riga FIR.

• Low-level significant weather (SWL) charts

SWL charts are issued at fixed forecast times of 0600, 0900, 1200, 1500 UTC and made available 1 hour 30 minutes before the fixed time. The chart provides a forecast of in-flight conditions for low-level flight operations up to FL100 within the Riga FIR and further into Europe, and covers the period of validity from 1 hour 30 minutes before to 1 hour 30 minutes after the fixed time.

The chart shows the position, direction and speed of movement of surface fronts, pressure centres and boundaries of significant weather zones for the fixed time.

The SWL chart depicts information about:

a. widespread mean surface wind speed more than 30 kt,

b. widespread surface visibility less than 5000 m and the weather phenomena causing the reduction in visibility,

c. thunderstorms (with or without hail),

d. clouds below FL100 and/or any occurrence of CB/TCU clouds: cloud amount, type, height of the base and top,

e. moderate or severe icing, except for icing in convective clouds,

f. moderate or severe turbulence, except for turbulence in convective clouds,

g. height of 0°C level, if it is below FL100,

h. volcanic eruption,

i. release of radioactive materials into the atmosphere.

The SWL chart does not depict information on:

• sea surface temperature and state of the sea,

• tropical cyclones,

• sandstorms/dust storms,

• mountain waves,

• mountain obscuration.

Additionally, a tabular forecast of upper winds/temperatures covering the Riga FIR for the same fixed time is included. Remarks concerning the expected weather phenomena hazardous to low-level flights within the Riga FIR and/or SIGMET/AIRMET applicable to the Riga FIR (SFC-FL100) at the time of issue of the forecast may also be included. The appropriate abbreviation “AMD” and “COR” indicates an amended and corrected forecast chart. Height indications in this form are given in hectofeet above mean sea level (AMSL).

• GAMET area forecasts

GAMET forecasts cover the Riga FIR, which is divided into four sub-areas (see Figure 1 GAMET/AIRMET areas), for validity periods 03-09 (only from 1 APR to 15 NOV), 06-12, 09-15, 12-18 and 15-21 UTC. Availability of the forecast is 1 hour before the beginning of the validity period. GAMET forecasts contain information on en-route weather phenomena hazardous to low-level flights (Section I) and additional information (Section II), as defined below:

SECN I

a) widespread mean surface wind speeds above 30 kt,

b) widespread horizontal surface visibility less than 5000 m, including the weather phenomena causing the reduction in visibility,

c) thunderstorms with or without hail (except for that for which a SIGMET has already been issued),

d) widespread areas of BKN or OVC clouds with height of base less than 1000 ft (AGL) and/or CB/TCU with heights of their bases and tops (AGL),

e) icing and turbulence (except for that occurring in convective clouds and for severe icing/turbulence for which a SIGMET has already been issued),

f) SIGMET messages applicable to the Riga FIR (SFC - FL100) and which are effective for the validity period of the forecast.

SECN II

g) pressure centres and fronts, their expected movements and developments, air mass characteristics,

h) surface wind direction and speed not included in SECN I,

i) upper winds and upper-air temperatures for the altitudes 1000 ft, 2000 ft, 5000 ft and 10000 ft,

j) surface visibility of 5000 m or more together with the weather phenomena,

k) cloud amount, type and heights of the bases and tops (AGL), not included in SECN I,

l) height indication of 0°C level(s) (AMSL), m) forecast of the minimum QNH values for each of two 3-hour periods,

n) sea-surface temperature and state of the sea for the sub-area S (see Figure 1 GAMET/AIRMET areas),

o) information on volcanic eruption (the name of the volcano), if volcanic ash clouds are significant for air traffic in the Riga FIR,

p) an outlook concerning hazardous phenomena expected to the end of the next forecast period.

The term “widespread” is to be regarded as a spatial coverage of more than 75 per cent of the area concerned. When a hazardous weather phenomenon is observed and/or forecast with a degree of coverage of less than 75 per cent of the area concerned, the phenomenon may be included in SECN I with the addition LCA (“locally”). The weather phenomenon location in GAMET/AIRMET is normally given by the sub-areas’ letter and numbers, for instance: S, 1, 2 and 3 (see boundaries and identifications of sub-areas on Figure 1 GAMET/AIRMET areas). An outlook is omitted from a GAMET forecast for the validity period 15-21 UTC.The forecasts are kept under continuous review and necessary amendments are prepared.

In addition to the GAMET service, low-level area warnings in the form of AIRMET messages are supplied, when necessary. More detailed information about the AIRMET service is provided in GEN 3.5.8.

An operator requiring the meteorological service or changes to the existing meteorological service shall notify, sufficiently in advance, ARO Riga no later than one month before any:

1. new routes or new types of flight operations are planned;
2. changes of a lasting character are to be made to scheduled operations;
3. other changes affecting the provision of the meteorological service are planned.

In the case of a non-scheduled flight, ARO Riga shall be notified in advance, as follows:

1. for flights within Europe, no later than 3 hours before the time at which the consultation and/or flight documentation are required;
2. for flights outside Europe, no later than 12 hours before the consultation and/or flight documentation is desired.

The notification made to the ARO Riga about an individual flight should contain the following information:

1. aerodrome of departure and estimated time of departure;
2. destination and estimated time of arrival;
3. route to fly and cruising level;
4. alternate aerodromes;
5. type of flight (VFR or IFR);
6. type of meteorological information requested by the flight crew member, either flight documentation and/or consultation;
7. time by which the consultation and/or flight documentation is required;

When a flight is a delayed, advanced or cancelled, ARO Riga shall be notified by the operator or a flight crew member as soon as possible.

All aircraft shall report whenever the following phenomena are encountered or observed during any phase of the flight within the Riga FIR: moderate or severe icing, moderate or severe turbulence, thunderstorms that are obscured, embedded, widespread or in squall lines, hail, volcanic ash cloud and low-level wind shear, even if previously reported to the aircraft.

Aircraft observations shall be reported by voice communication to the appropriate ATS unit at the time the observation is made or as soon thereafter as is practicable.

VOLMET broadcasts are in plain language (English), continuous H24 and are repetitive.

Table 2: GEN 3.5.7 for VOLMET service

Name of station	Call Sign Identification (EM)	Frequency	Broadcast period	Hours of service	Aerodromes/ Heliports included	Contents & format of REP and FCST & Remarks
1	2	3	4	5	6	7
RIGA	RIGA VOLMET (A3E)	127.655 (8.33 channel)	H24	H24	RIGA International	METAR+TREND, TAF, SIGMET
					VILNIUS	METAR+TREND, TAF, SIGMET
					TALLINN Ullemiste	METAR+TREND, TAF, SIGMET
					STOCKHOLM Arlanda	METAR+TREND, TAF
					MOSCOW Sheremetyevo	METAR+TREND, TAF
					MOSCOW Vnukovo	METAR+TREND, TAF
					ST.PETERSBURG Pulkovo	METAR+TREND, TAF
					HELSINKI Vantaa	METAR+TREND, TAF
					WARSAW	METAR+TREND, TAF

NOTES:

1. For non-8.33 kHz equipped State aircraft conducting flights to/from AD Riga, RIGA VOLMET FREQ is 127.650 MHz.

2. SIGMET information will be broadcast if an appropriate SIGMET message is issued and available.Otherwise, VOLMET will be broadcast "A/P NAME SIGMET NIL".

3. If a SIGMET message is issued, but cannot be processed automatically, a VOLMET will be broadcast "A/P NAME SIGMET UNREADABLE". Contact ATC for a particular SIGMET.

4. A VOLMET broadcast is updated when new information is received (half hourly METAR, TAF (including TAF AMD) or SIGMET (only for RIGA, TALLINN and VILNIUS FIRs).

Aircraft are allowed to receive VOLMET via data link. This service operates through the ACARS network and supports aircraft equipped with ACARS which is ARINC 623 compliant.

A D-VOLMET broadcast consists of the same information as Voice-VOLMET (Table GEN 3.5.7). Voice-VOLMET and D-VOLMET broadcasts are updated simultaneously.

A D-VOLMET is an additional service, so no NOTAM concerning possible interruptions to the service will be published.

Table 3: GEN 3.5.8 for SIGMET and AIRMET services

Name of MWO/ Location Ind.	Hours of service	FIR or CTA served	SIGMET validity periods	Specific procedures applied to SIGMET INFO	Procedures applied to AIRMET INFO	ATS unit(s) provided	Additional information
1	2	3	4	5	6	7	8
RIGA/ EVRA	H24	RIGA FIR	SIGMET/4 HR VA SIGMET/6 HR	TC SIGMET is not issued	AIRMET is issued only within the time period 06-21 UTC and 03-21 UTC from 1 APR to 15 NOV	Riga ACC/APP /TWR Liepaja AFIS	SIGMETs about SEV MTW, HVY DS/SS and AIRMETs about MT OBSC, MOD MTW are not issued due to meteorological reasons

General

For the safety of air traffic, the Meteorological Authority maintains an area meteorological watch and warning service. The service consists of a continuous weather watch within the Riga FIR, issuance of SIGMETs and the implementation of the AIRMET/GAMET concept. The Forecasting Division of Forecasting and Climate Department of LEGMC is designated to perform the functions of the MWO for the Riga FIR.

The Volcanic Ash Advisory Centre (VAAC) associated with the Riga MWO/ACC and responsible for providing the required advisory information is the VAAC Toulouse (France). SIGMETs for tropical cyclones (TC SIGMETs) are not issued for meteorological reasons.

Area meteorological watch service

A SIGMET message is issued when one of the following significant meteorological phenomena occurs and/or is expected to occur at cruising levels (irrespective of altitude):

• thunderstorm: obscured (OBSC TS), embedded (EMBD TS), frequent (FRQ TS), squall line (SQL TS), obscured with hail (OBSC TSGR), embedded with hail (EMBD TSGR), frequent with hail (FRQ TSGR), squall line with hail (SQL TSGR);
• severe turbulence (SEV TURB);
• severe icing (SEV ICE);
• severe icing due to freezing rain (SEV ICE (FZRA));
• volcanic ash cloud (VA CLD);
• radioactive cloud (RDOACT CLD).

In preparing SIGMET for volcanic ash clouds (VA SIGMET), the MWO Riga will use the relevant advisory information received from the VAAC Toulouse.

An AIRMET message is issued when the following weather conditions occur and/or are expected to occur and are not covered by the current GAMET:

• widespread mean surface wind speeds above 30 kt,
• widespread horizontal surface visibility less than 5000 m,
• isolated/occasional thunderstorms with or without hail,
• widespread areas of BKN or OVC cloud with height of base less than 1000 ft (AGL),
• CB or TCU clouds,
• moderate icing not associated with convective clouds,
• moderate turbulence not associated with convective clouds.

All SIGMETs/AIRMETs are issued in abbreviated plain language using ICAO abbreviations and are numbered consecutively for each day commencing at 0001 UTC. The period of validity of a SIGMET/AIRMET is not more than 4 hours with the exception of a volcanic ash SIGMET, which may have an extended validity of up to 6 hours. VA SIGMET are updated at least every 6 hours.

The MWO Riga transmits its own SIGMETs/AIRMETs to local ATS units (see table GEN 3.5.8), MWOs whose area of responsibility encompasses the adjacent FIRs, the responsible Regional OPMET Centre (ROC UK) and VAAC Toulouse in the case of VA SIGMET.

Warning service

1. Aerodrome warnings

Warnings for the protection of parked and moored aircraft or other equipment at Riga, Lielvarde and Liepaja aerodromeswill be issued by the Forecasting Division of Forecasting and Climate Department of LEGMC, if one or more of the following phenomena occurs or is expected to occur at the airport:

• strong surface wind,
• squall,
• freezing precipitation,
• heavy snow,
• air temperature fall to -30°C and below and increase of up to +30°C and over.

Quantitative criteria, as well as additional criteria necessary for the issuance of aerodrome warnings are specified at each aerodrome by arrangement between LEGMC and the users of the warnings. The warnings are issued in abbreviated plain language using ICAO abbreviations and distributed in accordance with the distribution list. The validity period of the warning is not more than 6 hours. The warning will be cancelled when a phenomenon is no longer occurring or no longer expected to occur at the aerodrome. The warning is understood to automatically cancel itself at the end of its validity period. If the phenomenon persists a new warning will be issued with the next sequence number and for a further period of validity. The numbering of aerodrome warnings starts every day at 0001 UTC is separate for each aerodrome.

2. Wind shear warnings

The Forecasting Division of Forecasting and Climate Department of LEGMC provides the wind shear warning service for AD Riga and AD Lielvarde. Wind shear warnings are prepared in abbreviated plain language using approved ICAO abbreviations and provide concise information about the reported and/or expected evidence of wind shear between the runway level and 1600 ft above it. The preparation of a wind shear warning and a confirmation of the warning previously issued is normally based on an aircraft report.

When wind shear conditions on the approach and/or climb-out below 1600 ft are forecast, a warning in the form of “WS FCST” may be issued. If a report of wind shear has been received from at least one aircraft and the existing meteorological conditions indicate that wind shear might be encountered, a warning in the form of “WS REP” is issued. In these cases, the validity period of the warning does not exceed 3 hours, and is normally limited to 1hour. If a pilot has reported wind shear in the approach or climb-out phases, but sufficient meteorological conditions do not occur for a wind shear forecast, a warning (“WS REP”) with a validity period of at least 30 minutes is issued. Wind shear warnings are numbered sequentially from 0001 UTC each day. Warnings are disseminated in a timely manner to Riga TWR/APP/ARO and Lielvarde TWR.

Automatic Terminal Information Service (ATIS)

ATIS broadcasts are available for AD Riga and AD Lielvarde. An ATIS broadcast consists of the elements in Table GEN 3.5.9 in accordance with Regulation (EU) No 923/2012, SERA.9010 (b), ICAO Annex 11, chapter 4.3.7. Each broadcast is identified by a designator in the form of a letter of the ICAO spelling alphabet. Designators assigned to consecutive ATIS messages are in alphabetical order.

Table 4: GEN 3.5.9 Other automated meteorological services, Part I

Service name	Information available	Area, route and aerodrome coverage	Telephone and telefax numbers, e-mail and website address Remarks
1	2	3	4
Automatic Terminal Information Service (ATIS -broadcast)	The following information is included in the broadcast in the following order: a. Riga International airport; b. arrival and departure indicator; c. contract type, if communication is via D-ATIS; d. message designator; e. observation (issue time) in UTC; f. type of approach to be expected; g. runway-in-use; h. holding delay, if appropriate; i. transition level; j.runway surface conditions (including runway condition code); k. essential operational information; l. surface wind direction and speed, including significant variation; m. visibility; n. runway visual range when applicable; o. present weather; p. cloud, if below 5000ft and/or CB/TCU, if the sky is obscured, vertical visibility; q. air temperature; r. dew point temperature; s. QNH; t. any available information on significant meteorological phenomena*; u. TREND forecast**; v. specific ATIS instructions.	RIGA FIR, in range 60 NM from Riga International Airport. The vertical coverage is from GND till FL 200.	Tel: +371 67300864 (PIN code 2812) Fax: NIL Email: NIL URL: NIL
Automatic Terminal Information Service (ATIS - broadcast)	The following information is included in the broadcast in the following order: a. "Lielvarde"; b. arrival and departure indicator; c. contract type, if appropriate; d. message designator; e. observation (issue time) in UTC; f. type of approach to be expected; g. runway-in-use; h.significant runway surface conditions; i. braking action; j. friction coefficient, if appropriate; k.holding delay, if appropriate; l. transition level; m. essential operational information; n. surface wind direction and speed, including significant variation; o. visibility; p. runway visual range when applicable; q. present weather; r. cloud, if below 5000 ft and/or CB/TCU, if the sky is obscured, vertical visibility; s. air temperature; t. dew point temperature; u. QNH; v. any available information on significant meteorological phenomena*; w. TREND forecast**; x. specific ATIS instructions. Note: Information on the status of the arresting system is available via Lielvarde TWR.	RIGA FIR, in range 35 NM from AD Lielvarde. The vertical coverage is from GND till 4000 ft	Phone: NIL Fax: NIL Email: NIL URL: NIL
* Only information about recent weather phenomena, wind shear, moderate/heavy turbulence and moderate/heavy icing for arriving and departing aircraft is included. Wind shear information is cancelled 30 min after the last aircraft report. Information of turbulence and/or icing is cancelled 2 hours after the last aircraft report. **TREND is available only in regular ATIS broadcasts (H+20 and H+50) based on local regular reports (MET REPORT). This should be noted by pilots when using ATIS broadcasts.

Note: Meteorological briefing at aerodrome is given in the individual aerodrome sections in AD 2 .

The broadcast is continuous and repetitive, regularly issued at every 20 and 50 minutes of each hour (based on local routine reports (MET REPORT)) and updated if necessary (based on local special reports (SPECIAL) and changes to air navigation information). Criteria for the issue of local special reports is shown in Table GEN 3.5.3.

The channel and operational hours of ATIS broadcasts are provided in AD 2, Tables EVRA AD 2.18 and EVGA AD 2.18.

Data link Automatic Terminal Information Service (D-ATIS)

Aircraft may receive ATIS via data link (D-ATIS). This service operates through the ACARS network and supports aircraft equipped with ACARS which is ARINC 623 compliant.

D-ATIS is available for Riga aerodrome only. Voice-ATIS and D-ATIS broadcasts are updated simultaneously.

As D-ATIS is an additional service, no NOTAM concerning possible interruptions to the service will be published.

METEO INF Service

Meteorological information broadcasts (METEO INF) are available at AD Ventspils for pilots.

Table 5: GEN 3.5.9 Other automated meteorological services, Part II

Service name	Information available	Area, route and aerodrome coverage	Telephone and telefax numbers, e-mail and website address Remarks
1	2	3	4
METEO INF broadcast*	The following information is included in the broadcast, in the following order: a. airport name; b. observation (issue) time in UTC; c. surface wind direction and speed, including significant variation; d. visibility; e. present weather**; f. cloud, if below 6000 ft, or if the sky is obscured the vertical visibility***; g. air temperature; h. dew point temperature; i. QNH; j. QFE.	AD Ventspils in the range approximately 110 NM from AD Ventspils. The vertical coverage is from GND till FL 095.	Tel:+371 63607210 Telex: NIL Fax: NIL Email: NIL URL: NIL
* METEO INF broadcasts for AD Ventspils are based on fully automated reports without human intervention. ** Only information about the following phenomena or combination thereof is available: rain, snow, drizzle, fog, haze, mist. *** Cloud type is not available.

The channel and operational hours of METEO INF broadcasts are given in part AD 2, table EVVA AD 2.18.

The broadcasts are continuous and repetitive, regularly issued every minute and updated, if necessary, based on local special reports. Criteria for the issue of local special reports is shown in Table GEN 3.5.3. The broadcasts during operational/non-operational hours of AD Ventspils are based on fully automated observations without human intervention. This should be noted by pilots when using such broadcasts.

Figure 1. GAMET/AIRMET AREAS