Practical Meteorology and Practical Navigation Ref: FTGU Pages , AIM MET Section

Review 1. 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: METARs/TAFs Need to know this as interpretation of weather is crucial to aircraft safety.

METARs 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 Z 33009KT 15SM FEW020 BKN091 M01/M06 A2993 RMK SC2AC3 SLP144=

Format of METAR Report type:METAR or SPECI Location type:CYYZ (Toronto) Date/Time:231700Z -> 23 rd day at 1700 Zulu Report modifier:AUTO or CCA, CCB Wind:00000KT -> Calm 35009KT -> 9 kts VRB03KT -> 3 kts 30015G25KT -> 15 gusting 25 kts 30015G25KT 260V340 -> 15 gusting 25 kts, wind is varying from 260 true to 340 true Visibility:5/8 SM, 1 ½ SM, P6SM, 15 SM RVR:R33/4000FT/U -> Rwy 33, 4000’ increasing R24L/1000V1200FT/D -> ?

Present Weather Codes Intensity or Proximity Descriptor Precipitation intensity refers to all forms at the time combined - ->Light (-RA = Light rain) Moderate (no qualifier) + Heavy (+SN = Heavy snow) VC = In the vicinity (within 5SM) MI = Shallow BC = Patches PR = Partial DR = Drifting BL = Blowing SH = Showers TS = Thunderstorms FZ = Freezing

Present Weather Codes Precipitation Obscuration DZ= Drizzle RA= Rain SN= Snow SG= Snow grains IC= Ice crystals (Vis ≤ 6 SM) PL= Ice pellets GR= Hail GS= Snow pellets UP= Unknown precipitation BR = Mist (Vis ≥ 5/8 SM) 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 Other PO= Dust/sand whirls (dust devils) SQ= Squalls +FC= Tornado or waterspout FC= Funnel cloud SS= Sandstorm DS= Duststorm

Sky Condition SKC- “sky clear”- no cloud present FEW- “few”- >0 to 2/8 oktas SCT- “scattered”- 3/8 to 4/8 oktas BKN- “broken”- 5/8 to <8/8 oktas OVC- “overcast”- 8/8 oktas CLR- “clear”- 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”

Remarks Include: Cloud layer type and opacity in oktas (SF5) General weather remarks Sea level pressure: SLP134 = hPa SPECI CYEL Z 36010KT 1SM -SHSN OVC008 RMK SF8 WNDS ESTD= METAR CYEL Z 36010KT 15SM -SHSN BKN030 BKN080 M05/M10 A3003 RMK SC6AC2 WNDS ESTD SLP190=

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:TAF or TAF AMD Location:CYYZ Issue Date/Time:281139Z: 28 th 1139 Zulu Period of validity:2812/2918 – Valid from 1200 Zulu on the 28 th to 1800 Zulu on the 29 th TAF CYYU Z 2020/ KT 3SM -SN OVC012 TEMPO 2020/2022 P6SM SCT015 BKN030 FM KT P6SM SCT015 BKN030 TEMPO 2022/2108 4SM –SHSN BKN015 RMK NXT FCST BY Z=

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. SCT040CB)

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. FM KT 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) -> PROB /2821 +TSRA

TAF CYTS Z 2020/ KT 11/2SM -SHSN OVC015 TEMPO 2020/2022 P6SM NSW OVC020 FM KT 6SM -SN FEW015 OVC040 TEMPO 2022/2102 2SM –SN OVC015 FM KT P6SM SCT020 BKN030 TEMPO 2102/2108 4SM -SHSN BKN020 RMK NXT FCST BY Z= TAF CYTL Z 2020/ KT P6SM SCT015 OVC025 TEMPO 2020/2108 2SM -SHSN BKN015 OVC030 BECMG 2102/ KT RMK FCST BASED ON AUTO OBS. NXT FCST BY Z=

Summary Topics covered today: How to read: METARs/TAFs Next class will be Navigation