AVIATION 120

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AVIATION 120

• Meteorology

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• METAR CYXX 131700Z 00000KT 20SM FEW050 SCT150
  SCT250 15/11 A3012 RMK SC2AC2CI0 FU SLP201
  METAR CYXX 131800Z 17002KT 20SM FEW040 FEW250
  17/10 A3012 RMK SC1CI0 FU CU ASOCTD SLP201
  METAR CYXX 131900Z 23002KT 20SM FEW025 FEW040
  FEW150 19/10 A3012 RMK CU1CU1AC1 FU SLP198
• TAF CYXX 131738Z 131818 22006KT P6SM SCT020
  SCT040 SCT120 TEMPO 1901 1SM FU BKN020 FM0100Z
  24005KT P6SM SCT050 SCT100 TEMPO 0103 4SM FU
  BKN050 BKN100 PROB30 0103 2SM FU FM0300Z
  23004KT P6SM BKN040 BKN090 TEMPO 0305 5SM -RA FU
  PROB40 0307 2SM FU FM0700Z VRB03KT P6SM BKN040
  TEMPO 0718 2SM FU PROB40 0718 1SM FU RMK NXT
  FCST BY 00Z

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Todays Agenda

• Weather observations at major aerodromes
• Aviation Routine Weather Report (METAR) AIM MET
  3.15
• Introduction
• Sample METARs
• Decoding the groups
• Report Type
• Station Indicators
• Date/Time
• Report Modifier
• Wind
• Prevailing Visibility
• Runway Visual Range (RVR)
• Present Weather
• Sky Conditions
• Temperature and Dewpoint
• Altimeter Setting
• Recent Weather
• Wind Shear
• Remarks

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Observations at Major Aerodromes

• Wind Information
• Measured by a single three-cup anemometer on a 10
  m mast with direct reading dials in the local
  weather observation office and/or ATS units.
• Wind direction and speed observations are
  averaged over 2 min with variation in the past 10
  min except where ATC units are using the
  Operational Information Display System.
• The Operational Information Display System
  provides continuously updated information to ATC
  units, including met info as follows
• MEAN WIND -Average wind for the
  last 2 min
• RUNWAY VISUAL RANGE (RVR) -Average for the last
  1 min
• ALTIMITER SETTING -Current
• Wind information will be issued as follows
• ATIS broadcast, Landing Information, Taxi
  Information, AWOS broadcast, LWIS Broadcast,
  take-off and landing clearance and pilot request
  are issued as MEAN WIND.

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• Cloud Information
• Information about cloud base height is obtained
  by use of laser ceilometers, ceiling projectors,
  ceiling balloons, pilot reports and observer
  estimation. Observations are provided to the
  local ATS units in the form of routine and
  special reports.
• Ceiling is the lesser of the height at which
  cumulative layers of cloud or smoke aloft obscure
  5/8 or more of the sky, or the vertical extent of
  the visibility as viewed through a surface based
  obscuring condition such as smoke or fog
  (vertical visibility).
• Temperature Information
• Temperature is read every hour from a mercury
  thermometer located in a ventilated screen
  (Stevenson Screen). Some locations have a remote
  readout of this information in the weather
  observation office or ATS unit.
• Runway Visual Range (RVR) Information
• RVR observations are obtained by transmissometers
  and forward-scatter sensors. RVR observations
  are representative of runway touchdown and
  midpoint visibilities averaged over 1 min and
  based on the light setting in use.
• Where RVR is accessible to the weather observer,
  RVR will be included in METARs and SPECIs when it
  is 6000 or less for the runway in use and/or the
  visibility is 1SM or less.

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Stevenson Screen
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Transmissometer
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Forward-scatter sensor
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Introduction to METARs

• Aviation Routine Weather Report (METAR) MET 3.15
• An international code that describes the actual
  weather conditions at a specified location and
  time as observed from the ground.
• Very detailed description can be found in the
  Manual of Surface Weather Observations (MANOBS).
• Normally taken and disseminated on the hour.
• National variations to the international code may
  be filed with the World Meteorological
  Organization (WMO)

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Sample METARs

• METAR CYYJ 080000Z 13007KT 30SM FEW040TCU
  SCT045CB BKN079 BKN230 17/11 A2989 RMK
  TCU2CB2AC2CI1 SLP123
• SPECI CYYJ 080029Z 12007KT 30SM -SHRA FEW035CB
  SCT040TCU BKN090 BKN230 RMK CB2TCU2AC2CI2
• METAR CYRV 080000Z AUTO 26019KT 9SM CLR 25/04
  A2974 RMK SLP051

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Decoding the METAR groups

• Report Type
• The code name METAR or SPECI is given first.
• Station Indicator
• Canadian weather reporting stations are assigned
  4 letter ICAO indicators commencing with C and
  followed by W, Y, or Z
• Stations are normally located within 1.6NM (3km)
  of the geometric centre of the runway complex.
• Aviation weather reporting sites are listed in
  the CFS.
• Date/Time of Observation
• The date (day of month) and time (UTC) of the
  observation is included in all reports.
• The official time of the observation (on the
  hour) is used for all METAR reports that do not
  deviate from the official time by more than 10
  minutes.
• In SPECI reports the time refers to the time of
  occurrence (hours and minutes) of the change(s)
  which required the issue of the report.

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• Report Modifier
• May contain two possible codes AUTO or CCA.
• Both codes may appear simultaneously AUTO CCA.
• AUTO will be used to indicate data collected by
  an AWOS. Should a human observer augment the
  AWOS, additional information will be added to the
  remarks group.
• CCA is used to indicate corrected reports. The
  second correction will be indicated with CCB etc.
• Wind
• Reports 2-min mean wind direction and speed along
  with gusts.
• Wind direction is always three digits in degrees
  true rounded to the nearest 10 degrees (last
  digit is always a 0)
• Wind speeds are two digits (3 only if required)
  in Knots.
• Calm wind is coded as 00000KT.

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• Wind (cont)
• Wind gust information will be included if gusts
  exceed the average wind speed by 5KT or more in
  the 10 minute period preceding the observation
  AND the peak gust reaches a maximum of 15KT or
  more. G indicates gusts and the peak gust is
  reported using two or three digits as required.
• Variations in direction are only included if
  during the 10 minute period preceding the
  observation, the direction varies by 60 degrees
  or more and the mean speed exceeds 3 knots. The
  two extreme directions are encoded in a clockwise
  order.
• Example METAR CYCG 091200Z 30015G25KT 260V340
• Prevailing Visibility
• Visibility is the greatest distance at which
  objects of suitable dimensions can be seen and
  identified.
• Prevailing visibility is maximum visibility
  common to sectors comprising of ½ or more of the
  horizon circle.
• Visibility is reported from eye-level (1.8m AGL).

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• Prevailing Visibility (cont)
• Visibility is reported in statute miles (SM) and
  fractions up to 3SM then whole miles. Note
  visibility from ocean stations is reported in
  nautical miles (NM).
• No maximum visibility for human observations.
• Lower sector visibilities which are half or less
  of the prevailing visibility are reported in the
  remarks group.
• Runway Visual Range (RVR)
• RVR of the touchdown zone of up to 4 available
  landing runways is reported as a 10 minute
  average, based on the operational runway light
  settings at the time of the report.
• Included when prevailing visibility is 1SM or
  less, and/or the RVR is 6000 or less.
• R is the group indicator followed by the runway
  designator.
• RVR is reported in hundreds of feet. M
  preceding the lowest measurable value or P
  preceding the highest, indicates the value is
  beyond the instrument range.

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• Runway Visual Range (cont)
• RVR trend is then reported if there is a distinct
  upward or downward trend from the first to second
  5 minute part-period such that the RVR changes by
  300 or more (encoded as /U or /D). If no
  distinct change is observed, it will be encoded
  with /N. Trend field left blank if trend isnt
  possible to determine.
• Variations in RVR may be reported for up to two
  runways. Variations may be reported as max and
  min values when the 1 minute mean varies by at
  least 20 (and by 150) from the 10-minute mean
  taken in the 10 minutes preceding the
  observation.
• EX R06L/1000V2400FT/U

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• Present Weather
• Comprised of weather phenomena which may be one
  or more forms of precipitation, obscuration or
  other phenomena.
• Weather phenomena may be preceded by one or two
  qualifiers, one which describes intensity or
  proximity, the other describes the phenomena in
  some other manner.
• Present weather is coded in accordance with the
  WMO Code, Table 4678 See MET 3.15
• Sky Conditions
• This group reports the sky condition for layers
  aloft.
• Vertical visibility is reported in hundreds of
  feet when the sky is obscured.
• Cloud layers are reported based on the summation
  of the layer amounts as observed from the surface
  up, reported as a height above the station
  elevation (AGL) in increments of 100 feet to a
  height of 10 000, and thereafter in increments
  of 1 000.
• Layer amount is the amount in eights (octas) of
  the whole sky (celestial dome) that is observed
  to be covered (not necessarily concealed) by a
  layer aloft or concealed by a surfaced based
  layer (fog, mist etc.).

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• Sky Conditions (cont.)
• Summation amount at any level is the amount in
  octas of the whole sky that is covered by layers
  at and below that level.
• Summation cannot exceed eight octas.
• Layer opacity represents the portion of the
  whole sky that is observed to be concealed
  (hidden, rendered invisible) by the layer. Layer
  opacity is reported in octas. No layer can
  exceed eight octas, nor can the total of the
  opacities for all layers exceed eight octas.
• If a layer does not conceal any part of the sky,
  opacity is zero.
• Opacity is reported in the RMK section of the
  METAR.
• Layer amounts are reported in octas of sky
  coverage
• SKC - No Cloud Present
• FEW - gt0 to 2/8 summation amount
• SCT - 3/8 to 4/8 summation amount
• BKN - 5/8 to lt8/8 summation amount
• OVC - 8/8 summation amount
• CLR - Clear below 10 000 as interpreted by
  an autostation (AWOS)

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OCTA OCTA OCTA OCTA OCTA OCTA OCTA OCTA
METAR CYXX 131900Z 23002KT 20SM SCT025 BKN040
OVC060 19/10 A3012 RMK CU4CU2AC1 FU SLP198
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High level Cirrostratus overcast cloud layer
displaying very little opacity. Eight octas sky
coverage with two octas of opacity.
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• Recent Weather
• This group reports recent weather of operational
  significance.
• The group indicator RE is followed, without a
  space, by the appropriate abbreviation(s) for
  weather observed during the period since the last
  scheduled report (METAR), but not observed at the
  time of observation. May be included in METARs
  and SPECIs.
• The following may be reported as recent weather
  phenomena
• Freezing precipitation
• Moderate or heavy drizzle, rain or snow
• Moderate or heavy ice pellets, hail or snow
  pellets
• Moderate or heavy blowing snow
• Sandstorm or dust storm
• Tornado or waterspout or funnel cloud
• Thunderstorm
• Volcanic Ash
• The same phenomenon is only reported as present
  weather and recent weather if it was of greater
  intensity during the period since the last
  routine report.

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• Wind Shear
• This group contains reports of low level wind
  shear (LLWS) within 1600 AGL along the takeoff
  or approach path of the designated runway.
• If the existence of wind shear applies to all
  runways, WS all RWY is used.
• Remarks
• Remarks will appear in reports from Canada,
  prefaced by RMK
• Remarks will include, where observed, layer type
  and opacity in eighths of sky concealed by clouds
  and/or obscuring phenomena, general weather
  remarks, and sea level pressure as required.
• Sea level pressure (SLP) will always be the last
  field of the METAR report.
• SLP022 converts to 1002.2 hPa, SLP994 converts to
  999.4 hPa
• Abbreviations for cloud types
• CI Cirrus NS Nimbostratus
• CS Cirrostratus ST - Stratus
• CC Cirrocumulus SF Stratus Fractus
• AS Altostratus SC - Stratocumulus
• AC Altocumulus ACC Altocumulus
  Castellanus
• CU Cumulus CUFRA Cumulus Fractus
• TCU Towering Cumulus CB - Cumulonimbus

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Whats Missing?

• METAR CWYM 151600Z AUTO ///// M03/ A2969 RMK
  SLP095
• METAR CWZZ 151700Z AUTO 21007KT 0SM 01/ A2952 RMK
  SLP024

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So you wanna be aN IFR pilot?

• METAR CYRB 151500Z 02018KT 3/4SM R35/5000FT -SN
  OVC015 M03/M05 A2961 RMK SN4ST4 SLP033
• METAR CYRB 151600Z 02024KT 3/4SM R35/6000FT -SN
  DRSN BKN016 OVC030 M04/M07 A2961 RMK SN3ST3SC2
  SLP035
• METAR CYRB 151700Z 02029KT 1SM R35/6000FT -SN
  DRSN BKN017 OVC030 M05/M08 A2962 RMK SN2ST4SC2
  SLP038
• SPECI CYRB 151720Z 02027KT 1SM R35/6000FT BLSN
  SCT020 BKN030 OVC230 RMK BLSN2ST2SC1CI0
• TAF CYRB 151740Z 151818 02025KT 1SM BLSN BKN007
  TEMPO 1823 4SM -SN SCT005 BKN030 FM2300Z 33020KT
  6SM BLSN BKN015 TEMPO 2307 1SM -SN BLSN BKN008
  FM0700Z 22028KT 1/2SM -SN BLSN VV002 TEMPO 0715
  2SM BLSN OVC010 FM1500Z 24018KT 4SM -SN BKN010
  TEMPO 1518 1SM BLSN OVC004 RMK NXT FCST BY 00Z

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