Meteorology - 405.12 International Aerodrome Forecast (TAF)

1. Meteorology - 405.12International Aerodrome Forecast (TAF)

2. Aerodrome Forecast (TAF) • A International Terminal Forecast (TAF) is a coded prediction of the surface weather expected that will affect landing and take-off at the aerodrome; • Wind, low level wind shear, prevailing visibility, significant weather and sky conditions are given for an area within 5 nautical milesof the aerodrome;

3. STATION IDENTIFIER & DATE/TIME ISSUED • Like the METAR the TAFs use the same 4 letter ICAO Station Identifiers, Example CYVR C denotes Canada Y denotes an airport VR denotes Vancouver • Day of month and UTC time of issue immediately follow station identification Example TAF CYVR 181740Z • Issued 4 times a day (International Airports) about 20 minutes prior to the period of coverage • Valid from the time of issue until it is amended or until the next scheduled TAF is issued • when a new TAF is issued, it automatically cancels the previous one

4. TAF – Valid Period ● Normal valid period is 24 hours Example: TAF CYWG181740Z 1817/1917 ● except for international airports which has an extended valid period up to 30 hours ● with this change a two digit date has been added to all times and to all times in the change groups throughout the body of the TAF; Example: TAF CYYZ 081140Z 0812/0918 13015KTP6SM BKN030 TEMPO 0818/0823 17025G40KT OVC020TCU BECMG 0823/0901 SCT015 BKN020 FM091000 BKN 020 ● TAFs can be amended if the current TAF no longer represents the expected weather ● Letters “AMD” will appear in the header line prior to the text of the forecast Example: TAF CYVR 181640Z 18171917 AMD

5. WIND FORECAST • Encoded same as METAR; • Direction use 3 digits to the nearest 10º true • speed in knots • Speeds equal to or greater than 100KT use 3digits Example 24110KT (Direction 240°true / Speed 110KT) • Calm wind forecasted as 00000KT • Wind speeds of 3KTs or less may be encoded as variable direction e.g. VRB03KT. Sample wind group: 24020G35 indicates - forecasted direction 240° True - forecasted speed 20KT with gusts to 35KT

6. Low Level Wind Shear • Low Level Wind Shear – forecasts of low level (non-convective) wind shear will be included whenever strong wind shear, which could adversely affect aircraft operation within 1,500 ft AGL, can be adequately predicted Example: WS 011/20050KT - Wind Shear at 1,500ft AGL over the aerodrome; and - Wind is forecasted to be 200° T at 50KTs

7. VISIBILITY FORECAST • Prevailing visibility is forecast in statute miles (SM) and fractions up to 3 miles, then in whole miles up to 6 miles. • however, when visibilities are forecasted to be greater than 6 SMs, will be coded as P6SM. Example: TAF CYWG 121140Z 1211/1311 24020G35KT P6SM FM 130200 3/4SM BR

8. FORECAST WEATHER • immediately following the (visibility • same abbreviations/codes for weather phenomena as in METARs • intensity and proximity qualifiers, descriptors, precipitation and obscuration are included as required • however, NSC (no significant cloud) and CAVOK (ceiling and visibility OK) not used in TAFs in Canada • Example: 3SM –SHRA 3 STATUTE MILES IN LIGHT RAIN SHOWERS

9. FORECAST SKY CONDITION • is encoded same as in a METAR • cloud amounts are cumulative, therefore, amounts include the sum of any layer below • SKC, FEW, SCT, BKN, OVC and VV • Cloud type are not reported except in the case of CB cloud layers • Cloud heights reported above ground level (AGL) or Station Elevation Example: 24020G35 3SM -SHRA SCT015 BKN040CB

10. FORECAST CHANGES • weather does not stay static during a 12 or 24 hour forecast period • the valid period of the forecast may therefore be divided into several self-contained “part periods” • each representing segments of time during which the weather is expected to stay generally constant • the abbreviation NWS, for no significant weather, may be used Example: CYWG 191640Z 19172017 36010KT P6SM SKC FM200200 VRB03KT P6SM BKN250 BECMG2007/2009 SCT040 BKN120 FM201000 VRB03KT P6SM –SHRA BKN050 OVC120 PROB30 2010/2014 VRB15G25KT 3SM TSRA BKN020 OVC040CB RMK NXT FCST BY 200000Z

11. FORECAST CHANGES • FM100400 • FM indicates a permanent change is forecasted to occur rapidly • indicates the beginning of a new part period, starting at the indicated time, and may be read as “forecast to occur on the 10th day at 0400Z • since FM is a permanent change group all weather elements preceding this indicator are superseded by the forecasted conditions following the FM indicator Example: .....24015G25KT 3SM -SHRA SCT015 OVC040 FM100400 20010KT P6SM SCT020 OVC030…

12. FORECAST CHANGES • BECMG 1005/1007 - the indicator BECMG (read as becoming) indicates a gradual change from one condition to another • BECMG indicates a permanent change in some elements of the forecasted weather • therefore, “BECMG 1005/1007”- is forecasting a gradual change in weather to occur over a 2 hour period between 100500 to 100700Z • only those conditions expected to change need to be indicated Examples:…FM100400 12025G35KT 3SM -SHRA SCT015 OVC040 BECMG 1005/1007 18015KT 1SM SHRA OVC 020 FM251700 28008KT P6SM FEW60 SCT220 BECMG 2523/2602 30015G25 FM 260100….

13. FORECAST CHANGES • TEMPO 1009/1013. Change group from 0900Z on the 10th day t0 1300Z on the 10th day temporary fluctuation are forecast to occur between the times indicated to some of the weather elements • only those elements expected to fluctuate/change are included. • Examples..... FM100900 VRB03KT 3SM -RA BR OVC020 TEMPO 1009/1013 1SM RA BR..... FM 182000 1/4SM-DZ FG VV001 TEMPO 1822/1901 1SM BR SCT002 OVC004…….

14. FORECAST CHANGES • PROB 30 1004/1007- Indicates a 30 percent probabilitythat 2SM BR will occur within a 3 hour period from 0400Z on the 10th day and 0700Z on the 10th day; and • use is restricted to aviation hazards like thunderstorms, freezing rain, low level wind shear below 1500ft AGL; or ceiling and visibility values important to aircraft operations • and probabilities less than 50 percent. • Example; FM101000 VRB03KT P6SM –SHRA BKN050 OVC120 PROB 30 1010/1007 2SM BR

15. AUTO OBSERVATIONS- (AUTO OBS) • AUTO OBS abbreviation in remarks section indicates forecast based on observations from an automatic weather station (AWOS) data Example TAF CYTE 101138Z 1012/1100 30012KT P6SM BKN025 TEMPO 1013/1018 3SM -SN BKN015 FM101800 30020G30KT P6SM BKN025 TEMPO 1018/1101 3SM -SN BLSN OVC015 RMK FCST BASED ON AUTO OBS. NXT FCST BY 101900Z=

16. Confirmation Stage and Performance Check

17. Sample TAFs - Cadets to Read in Class CYQQ 211140Z 2112/2212 33005KT P6SM SKC BECMG 2118/2120 04005KT BECMG 2201/2203 33010KT RMK NXT FCST BY 221800Z= CYTR AMD 211900Z 2119/2218 35005KT P6SM BKN030 BKN090 BECMG 2114/2117 35010KT SCT030 SCT100 SCT250 FM212300 VRB03KT P6SM SCT030 BKN250 BECMG 2207/2209 BKN025 BKN140 RMK NXT FCST BY 221800Z= CYYZ 211140Z 2112/2218 34010KT P6SM SCT060 TEMPO 2115/2118 5SM BR BKN020 BKN060 BECMG 2211/2212 02010KT RMK NXT FCST BY 221800Z=

18. Aerodrome Forecasts (TAF) Exercise 405.12 CYYC 211438Z 2115/2212 18006KT P6SM SKC BECMG 2119/2121 14010KT RMK NXT FCST BY 211800Z= CYQL 211138Z 212224 25003KT P6SM SKC BECMG 2114/2116 20008KT BECMG 2118/2120 13008KT RMK FCST BASED ON AUTO OBS. NXT FCST BY 211800Z= CYQR 211138Z 2112/2124 VRB03KT P6SM SKC PROB30 1214 1SM BR BECMG 1416 27008KT FM211700 27012KT P6SM FEW050 RMK NXT FCST BY 211800Z= CYVR 211138Z 2112/2218 27005KT P6SM BKN250 BECMG 2114/2116 28010KT FM211800 30012KT P6SM SCT050 BKN250 PROB30 2118/2200 VRB20G35KT 3SM TSRA BKN040CB FM220400 30008KT P6SM BKN120 TEMPO 2206/2212 P6SM -SHRA RMK NXT FCST BY 211800Z= Using the TAFs above answer the following questions: 1. The TAF for CYYC indicates that the forecasted winds for the forecast period will be? 2. What is the lowest ceiling being forecasted for CYVR? 3. What is the issue time and valid time for the CYQL TAF? 4. What is the lowest visibility being forecasted for CYQR? 5. When is the next scheduled forecast for CYQL ? 6. Which TAF is based on a AWOS observations? 7. In the CYVR TAF what are the changes of having a CB cloud present? 8. What is the highest wind being forecasted in the above TAFs?