Meteorology 3

CI Norwood
Meteorology 3
Ref: FTGU Pages 158-172, AIM MET Section
What are the four air masses that affect Canada?
2. What is a Front?
3. What does a thunderstorm need in order to form?
Topics to be covered
 Weather services and maps
 How to read:
 Surface/Upper level/Prog charts
 GFAs/FDs
 Need to know this as interpretation of weather is
crucial to aircraft safety.
Aviation Weather Information
Service (AWIS)
 NavCanada FSS system
 Provides weather information to help pilots before and
during flight
 Service puts pilots in contact with specialists who help
pilots make educated decisions and calculations based
on factors relating to weather conditions
Aviation Weather Briefing Service
 Fully interpretive weather briefing service available
from the Flight Information Centers (FIC)
Access through toll free number
Equipped with complete set of weather products,
including satellite and radar imagery
Specialists trained to interpret the weather data for the
needs of users in aviation industry, as well as offer
advice on particular weather situations
Documents for long distance flight available on
Flight Service Stations (FSS)
 Staffed by flight information specialists
 Situated at various aerodromes across Canada
 Services offered:
 Enroute Flight Information Service (FISE)
 Flight Planning Service
 Surface weather observation service
 Aviation Weather Information Service (AWIS)
 Aviation Weather Briefing Service (AWBS)
 VFR Alerting Service
 NOTAM service
Pilot’s Automatic Telephone Weather
Answering Service (PATWAS)
 Continuous recording of certain local weather
information intended for aviation is issued by some
FSS and is available by telephone
 Include:
 Issuing station name and introduction, Instructions
 TAF and FDs
 Freezing level, icing and turbulence
 Times of sun-rise and sun-set
Significant Meteorological
Advisories (SIGMET)
 Short term alerts to aircraft in flight concerning potentially
hazardous weather conditions
 Issued for the following phenomenon:
 Active thunderstorm cells
 Squall lines
 Severe hail
 Severe turbulence
 Severe icing
 Significant mountain wave effects
 Hurricanes
 Far-reaching sand or dust storms
 Volcanic ash
 Low-level wind shear
Automated Terminal Information
Service (ATIS)
 Continuous broadcast of recorded non-control
information at busier airports
 Essential information:
 Weather information
 Active runways
 Available IFR approach
 NOTAMs, etc.
 Pilots listen to ATIS prior to contacting control unit
 Reduce controller’s workload and relieve frequency
 Updated every hour or when necessary
 Comes with a letter designator to ensure most current
version is in use
High Altitude SIGWX Charts
 Shows SIGWX for a specific flight range:
 Icing, turbulence and convective activity
 Flight between FL250-FL630 (380-75 hPa)
 Valid at 0000, 0600, 1200, 1800 UTC
 Issued by the National Weather Service of the United
States government; the equivalent of the Canadian
Weather Service
Mid-level SIGWX Charts
 Shows SIGWX for a specific flight range:
 Icing, turbulence and convective activity
 Flight between FL100 – FL240 (700-400 hPa)
 Valid at 0000, 0600, 1200, 1800 UTC
 Issued by the Canadian meteorological centre of
Environment Canada
 Based on information collected from all the aviation
weather forecast centers of the country
Surface Weather Charts
 Graphical depiction of:
 MSL pressure patterns
 Surface location of fronts
 Surface precipitation and obscurations to vision
 Pressure patterns can be considered accurate up to
3,000 feet
 Observed every six hours, issued 2 to 3 hours after
Upper Level Analysis Charts
 Computer generated graphical depiction of reported
atmospheric conditions at the pressure level, which
 Wind speed and direction
 Temperature
 Moisture content
 Frontal surface locations
 Measured twice a day, at 0000Z and 1200Z
 Issued for 850 mb (5,000’), 700 mb (10,000’), 500 mb
(18,000’) and 250 mb (34,000’)
Upper Level Analysis Charts
 Height: Contours represent the height of the pressure
level in decameters, spaced 60 m apart on except on
250 mb charts where it’s spaced 120 m
 Temperature: Analysed on 850 and 700 mb, drawn as
dashed lines at 5 degree intervals. Can be read in the
top corner of station plots at higher altitudes
 Wind speed and direction: Can be determined by
direction and spacing of contours, or by isotachs on
the 250 mb chart, given in 30 kt intervals
Upper Level Wind Chart
 Provides the forecast of temperature and winds for a
given flight level
 Three distinct geographic regions:
 Essentially the same as the FDs except only one flight
level can be seen due to graphically depicted form
Computer generated
Wind direction in relation to True North
Valid at 00, 06, 12, 18 UTC
National Weather Service (US government)
Surface Prognostic Charts
 Graphical forecast of weather at the surface
 For the purposes of aviation, Canada does not issue
surface prognostic charts, American ones can be used
 Issued for latest surface analysis, 12-, 24-, 36- and 48hour forecast times
 Shows pressure systems and patterns, front positions,
precipitation and ground obscurations
48-Hour Forecast
 Aviation Routine Weather Report
 Observation of the actual weather from the ground
 Issued on the hour and valid only for the time taken
 A SPECI is a special weather report that when a
significant change in the weather has occurred
 Each METAR and SPECI is composed of several
standard groups
 METAR CYKZ 202000Z 33009KT 15SM FEW020
BKN091 M01/M06 A2993 RMK SC2AC3 SLP144=
Format of METAR
Report type:
Location type:
Report modifier:
 Visibility:
 RVR:
CYYZ (Toronto)
231700Z -> 23rd day at 1700 Zulu
00000KT -> Calm
35009KT -> 350°T @ 9 kts
VRB03KT -> Variable @ 3 kts
30015G25KT -> 300°T @ 15 gusting 25 kts
30015G25KT 260V340 -> 300°T @ 15 gusting
25 kts, wind is varying from 260 true to 340
5/8 SM, 1 ½ SM, P6SM, 15 SM
R33/4000FT/U -> Rwy 33, 4000’ increasing
R24L/1000V1200FT/D -> ?
Present Weather Codes
Intensity or Proximity
 Precipitation intensity refers
 MI = Shallow
to all forms at the time
- ->Light (-RA = Light rain)
Moderate (no qualifier)
+ Heavy (+SN = Heavy snow)
VC = In the vicinity (within
 BC = Patches
 PR = Partial
 DR = Drifting
 BL = Blowing
 SH = Showers
 TS = Thunderstorms
 FZ = Freezing
Present Weather Codes
 DZ
 BR = Mist (Vis ≥ 5/8 SM)
 RA
 SN
 SG
 IC
 PL
 GR
 GS
 UP
= Drizzle
= Rain
= Snow
= Snow grains
= Ice crystals (Vis ≤ 6
= Ice pellets
= Hail
= Snow pellets
= Unknown precipitation
 FG = Fog (Vis < 5/8 SM)
 FU = Smoke (Vis ≤ 6 SM)
 DU = Dust (Vis ≤ 6 SM)
 SA = Sand (Vis ≤ 6 SM)
 HZ = Haze (Vis ≤ 6 SM)
 VA = Volcanic ash (Any vis)
Present Weather Codes
 PO = Dust/sand whirls
(dust devils)
 SQ = Squalls
 +FC = Tornado or
 FC = Funnel cloud
 SS = Sandstorm
 DS = Duststorm
Sky Condition
- “sky clear”
- “few”
- “scattered”
- “broken”
- “overcast”
- “clear”
- no cloud present
- >0 to 2/8 oktas
- 3/8 to 4/8 oktas
- 5/8 to <8/8 oktas
- 8/8 oktas
- clear below 10,000’ as
interpreted by an autostation
 Significant convective cloud (CB or TCU) are identified
with the sky condition group
SCT025TCU – Scattered TCUs at 2500’
 A ceiling is said to exist at the lowest BKN or OVC layer
 All cloud heights are in AGL
 Temperature/Dewpoint:
10/05 – Temp: 10°C,
Dewpoint: 05°C
05/M01 – Temp:
05°C, Dewpoint: -1°C
 Altimeter setting:
A2992 – 29.92” Hg
A3031 – 30.31” Hg
 Recent weather:
Significant weather
 Wind shear:
Low level windshear within 1600’
AGL along t/o or landing path or a
specific runway “WS R33L”
 Include:
 Cloud layer type and opacity in oktas (SF5)
 General weather remarks
 Sea level pressure: SLP134 = 1013.4 hPa
 SPECI CYEL 201958Z 36010KT 1SM -SHSN OVC008
 METAR CYEL 201900Z 36010KT 15SM -SHSN
BKN030 BKN080 M05/M10 A3003 RMK
Aerodrome Forecast (TAF)
 Description of the most probable weather conditions
with the most probable time of occurrence
Gives weather within 5 NM of the centre of the
runways complex
Uses the same weather coding as the METAR, although
forecast times are included
Altitudes in AGL
Degrees are given in True
TAF Format
 Report type:
 Location:
 Issue Date/Time: 281139Z: 28th day @
1139 Zulu
 Period of validity: 2812/2918 – Valid from
1200 Zulu on the 28th to
1800 Zulu on the 29th
 TAF CYYU 201948Z 2020/2108 30012KT 3SM -SN OVC012
TEMPO 2020/2022 P6SM SCT015 BKN030
FM202200 30010KT P6SM SCT015 BKN030 TEMPO
2022/2108 4SM –SHSN BKN015 RMK NXT FCST BY
TAF Format – Significant Weather
 Uses the same format as the METAR
 VC or ‘vicinity’ in a TAF means 5 – 10 NM
 A maximum of 3 significant weather groups are
allowed per forecast period
 If one significant weather groups is forecast to change,
all other that will exist will be indicated
 CB layers will be identified with cloud groups (i.e.
Change Groups
 In all change groups, multiple elements are considered
single entities
 “SCT030 BKN050 OVC080...change
indicator...BKN050” would mean that after the change
indicator, there would only be a broken layer at 5000’
 FM – Permanent change (rapid) – All forecast
conditions are superseded by this.
FM280945 30015KT P6SM BKN030
Change Groups
 BECMG – Permanent change (gradual) – When the conditions
evolve over a period of time (one to two hours)
BECMG 2808/2809 OVC030
Any weather element not indicated as part of the BECMG group
remains the same
TEMPO – Transitory change group – Temporary fluctuations in
some or all weather elements during a specified period
TEMPO are only used if the condition is expected to last less
then an hour, if more, than a time period would be given (i.e.
TEMPO 2812/2815 1SM RA BR)
PROB – Probability group – Probability of alternative weather
values occurring (that are considered hazards to aviation) ->
PROB30 2817/2821 +TSRA
 TAF CYTS 201948Z 2020/2108 33012KT 11/2SM -SHSN
OVC015 TEMPO 2020/2022 P6SM NSW OVC020
FM202200 33012KT 6SM -SN FEW015 OVC040 TEMPO
2022/2102 2SM –SN OVC015
FM210200 31010KT P6SM SCT020 BKN030 TEMPO
2102/2108 4SM -SHSN
 TAF CYTL 201948Z 2020/2108 33015KT P6SM SCT015
OVC025 TEMPO 2020/2108 2SM -SHSN BKN015 OVC030
BECMG 2102/2104 31012KT
What is a GFA?
 Series of weather charts that are adjusted for pre-flight
planning in Canada
 Gives the most probable weather conditions under
24,000 feet (400 mb)
Issue and Validity Periods
 Issued four times daily (2330, 0530, 1130 and 1730 UTC)
 Valid at 0000, 0600, 1200 and 1800 UTC
 Each GFA has six charts covering 3 time periods (near-
time, 6-hour and 12-hour forecasts)
 Two charts issued at a time for three consecutive time
 Two types of GFA: Clouds and Weather/Icing,
turbulence and Freezing level
Areas of Coverage
 Canada is divided into 7 regions:
 Arctic, Yukon-NWT, Pacific, Prairie, Ontario-Quebec
and Atlantic
 There is an additional forecast region that is created
on demand in the arctic
Units of Measurement
 Wind speeds are given in knots (KTS)
 Direction is in degrees true
 Cloud heights in hundreds of feet
 Distances in nautical miles (NM)
 Visibility in statute miles (SM)
 All times are in UTC
 Pressure in millibars (mb)
 All heights are given in feet Above Sea Level (ASL)
Title Box
Legend Box
Comments Box
Weather Information Section
Title Box
 Consists of:
 Chart name
 Issuing station’s identifier
 Region
 Type of chart
 Issue date
 Validity
 Includes symbols that
may be used in the chart
 Symbols are consistent
with those used in
Significant Weather
Prognosis Charts
 Includes a scale in
nautical miles for
Comments Box
 Includes information that
the forecaster believes is
 Also used to prevent
clutter in the weather
 Always includes the
standard phrases in the
bottom box
 The IFR outlook is located
here in the 12 hour forecast
Weather Information Section
 Graphic representation
of the clouds and
weather conditions or
the icing, turbulence and
freezing level forecast for
a given time
 What are the validity periods of a GFA?
 Near-time, 6-hour, 12-hour and 12 hour IFR outlook
 What are the units of measurement?
 Wind speeds are given in knots (KTS)
Cloud heights in hundreds of feet
Visibility in statute miles (SM)
All times are in UTC
Pressure in millibars (mb)
All heights are given in feet Above Sea Level (ASL)
Synoptic Features
 If the speed of any system
is greater than 5 knots, an
arrow will give direction
and speed of the system
 The centre of this
depression is moving
eastward at 15kts with an
associated cold front
moving south-east at 10kts
 A scalloped border
shows the region where
cloud is predicted
 In areas of unorganised
clouds, no scalloped
border is given
 Cloud bases and tops are
given in feet ASL along
with coverage and type
Weather and Obstructions to
 Obstructions to visibility
Unrelated to precipitation
are given only when it is
predicted to be less than
6 SM
 The type of obstruction
is given after in standard
 Solid lines indicated
continuous precipitation
 Dotted area indicate
showery precipitation
Isobars and Surface Winds
 Isobars are shown in 4
millibar intervals (i.e.
1000, 1004, 1008)
 Surface wind conditions
in excess of 20 KTS are
indicated on GFA
 Wind gusts have a “G”
included with the wind
 Depicted when moderate
or severe
icing/turbulence is
 Information included is
type, severity and height
that it will be
Freezing Level
 Indicated by dashed contour lines
 Height given above sea level given in 2500 foot
intervals starting at the surface (SFC)
Amendments and Corrections
 Automatically amended
 GFAs will be reissued in
case a significant error
that will cause
misinterpretation of the
 Indicated by CCA, CCB,
just like in a METAR
Give an estimate of winds and temperatures to be found at
determined altitudes
Issue and Validity
 Time of issue and period of validity are indicated on
the report
 Data collected by 32 stations in Canada, 2 times a day
at 0000Z and 1200Z
 Winds are in degrees True, altitudes in ASL
 No temperatures for 3000ft
Flight Planning and Weather
 Up-to-date info must be obtained and analyzed prior
to each flight in order to properly prepare for all
significant weather which might affect the flight
 Required to choose a cruising altitude, calculate
ground speed, drift, flight time and fuel consumption
 Basic information to obtain and review for VFR:
 METARs and TAF: departure, destination and enroute
 FD: for expected cruising altitudes
 GFA: overview of weather affecting the region
 NOTAMs: all significant info/changes for pilots
 Topics covered today:
 Weather services and maps
 How to read:
Surface/Upper level/Prog charts
 Need to know this as interpretation of weather is
crucial to aircraft safety.
 Next class will be Navigation
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