A W O S & M E T A R S

1. A W O S & M E T A R S 405.11

2. Weather Observing Systems • Weather observation are taken every hour at selected aerodromes throughout Canada and U.S.A. These observations are taken by trained observers or by an automatic weather station; • The Automated Weather Observation System (AWOS) is designed to electronically collect weather data and to disseminate partial or full surface weather observations; • Two types AWOS and Limited Weather Information System (LWIS); • AWOS have a full suite of sensors and the LWIS is a more basic system, capable of measuring wind, altimeter, temperature and dewpoint; • Both systems may be equipped with a voice generated message of the report via VHF radio or by telephone; and • Sometimes unreliable due to the computer software or instrument malfunctions

3. METARS • WHAT IS IT? An international standard, coded report of the weather conditions as it exists at a given time and place taken hourly. It is an international code format. Approvedby the WMO, a branch of the UN. - it describes the occurring weather within 3km of the observation site; and - vicinity phenomena reported within 8km of the observing site.

4. TYPE OF REPORT • METAR: hourly weather report (issued on the hour); and • SPECI: special weather observations issued at times other than on the hour, as a result of a significant weather change. • Notes: 1.there is no provision in METAR(s) for reporting significant changes in weather when they occur on the hour (not a SPECI) 2.if “LWIS” follows the type of report, this indicates that the observation has been derived from a limited suite of automated weather sensors

5. IDENTIFICATION • INTERNATIONAL - 4 LETTERS EXAMPLE CYHZ - Halifax CYWG - Winnipeg CYQQ - Comox KSEA - Seatle, USA EDDT - Berlin, Germany NZOA - Omarama, New Zealand

6. ICAO STATION IDENTIFIER • CYWG C - country (Canada) Y - airfield identifier (note “Y” or “Z” indicates reporting station co-located with a airport, “W” indicates not co- located with airport, and “U” indicates co-located with radio beacon) WG - Winnipeg • KSEA K - country (U.S.A.) SEA - Seattle

7. OBSERVATION DATE/TIME • the date and time of the observation are always given in six digits, using universal coordinated time (UTC); • A correction to a METAR or SPECI report is denoted by the letters “CCA” (first correction) and “CCB ” (for the second correction) EXAMPLES: METAR CYWG 132000Z CCA 13th day of the month 2000 UTC - 1st correction METAR CWQC 211200Z LWIS 21st day of the month 1200 UTC – Limited suite automatic weather sensors report

8. SURFACE WINDS • 2 minute mean wind - preceding observation • Wind Direction- degrees true, always 3 digits to the nearest 10 degrees. If direction varies 60° or more and the mean speed exceeds 3 KTs, during the 10 minute period preceding the observation, it is reported 3 digits, the letter “V” and 3 more digits” Example 060V130 Indicates wind direction is varying from 060° to 130° true in the 10 minutes preceding the observation

9. SURFACE WINDS • Wind Speed • the next two digits are speed in knots (KT) • speeds equal to or greater than 100KT use 3digits • calm winds encoded 00000KT • VRB (speed group) indicates variable direction and speeds 3KT or less Example METAR CYEG 151200Z 270VRB •Wind Character - Gust is reported if wind speeds exceed the mean wind by 5 knots or more and the peak gust reaches a maximum speed of 15 knots or more in the 10 min period preceding the observation. The gust is reported using 2 or 3 digits as required Example METAR CYWG 132000Z 30015G25KT

10. PREVAILING VISIBILITY • Defined as - the greatest visibility common to 1/2 or more of the horizontal circle (observation point); • reported in statute miles and fractions in Canada/U.S.A. (statute miles & fractions up to three miles, then in whole miles up to 15 miles/units of 5 miles thereafter); and • Lower visibility in any one sector, which are half or less of prevailing visibility, are reported as supplementary information in the remarks section at the end of the METAR. Example METAR CYWG 132000Z 30015KT 2SM BR OVC040 18/18 A2992 RMK ST8 VSBY NE 1 SLP134 Prevailing visibility is 2SM /in RMK visibility NE 1SM

11. RUNWAY VISUAL RANGE (RVR) RVR – reported whenever prevailing visibility is 1 mile or less and/or the RVR is indicating 6,000 ft or less (10 minute average) “R” is the group identifier which precedes a 2-digit group that designates the runway; Example R36 – indicates RVR visibility for runway 36 - followed by a letter L, C, or R (left, centre or right) if the airport has parallel runways; Example R36L Followed by a / and a 4-digits group reporting the visual range in hundreds of feet Followed by letters FT to indicate that the units for RVR are feet Example R36L/4000FT – indicates along R36 left/visual visibility is 4000feet

12. RUNWAY VISUAL RANGE (RVR) • Followed by a / if a tendency (trend) is reported when a distinct upward or downward change of 300FT or more is observed by using “D” downward, “U” upward or “N” no change. If not possible to observe the tendency, the tendency indicator is omitted. Example METAR CYWG 132000Z 30015 3/4SM R36L/4000FT/D RVR reported - along Runway 36left Vertical visibility 4000 feet - the trend indicates an downward (deteriorating) change of 300 feet or more

13. PRESENT WEATHER Present weather is comprised of weather phenomena (precipitation, obscuration, or other phenomena) preceded by one or two qualifiers (intensity or proximity to the station and descriptor) - Intensity modifier“-” for “light” No modifier “moderate” “+” for “heavy” - VC Proximity qualifier “for vicinity” reported when these phenomena observed within 8km(5SM) but are not happening at the station. When VC is associated with “SH” the type and intensity of precipitation is not specified because it cannot be determined. Examples: VCSH = showers in the vicinity, VCFC = funnel cloud in the vicinity

14. DESCRIPTORS SH SHOWERS BL BLOWING MI SHALLOW PR PARTIAL FZ FREEZING DR LOW DRIFTING BC PATCHES TS THUNDERSTORM PRECIPITATION RA RAIN DZ DRIZZLE IC ICE CRYSTALS PL ICE PELLETS SN SNOW SG SNOW GRAINS GR HAIL GS SNOW PELLETS UP UKNOWN PRECITATION (AWOS only) PRESENT WEATHER ABBREVIATIONS

15. OBSCURING PHENOMENA HZ HAZE SA SAND DU DUST FU SMOKE FG FOG (VSBY <5/8) BR MIST (VSBY  5/8) VA VOLCANIC ASH OTHER +FC TORNADO or WATERSPOUT FC FUNNEL CLOUD SS SAND STORM +SS SAND STORM (VSBY <5/16) DS DUSTSTORM +DS DUSTSTORM (VSBY <5/16) SQ SQUALLS MORE ABBREVIATIONS

16. SKY CONDITION • The celestial dome is divided into 8 segments, each called an okta • Codes for sky cover amounts are: SKC…………… Sky clear – no cloud present or partially obscured FEW ................... Few Trace to 2/8 SCT……………. Scattered 3/8 to 4/8 BKN …………… Broken 5/8 to 7/8 OVC……………. Sky Overcast 8/8 VV………………sky obscured Sky cover amounts are cumulative therefore, layer amounts include the sum of any layers below. A cloud ceiling is said to exist at the the height of the first layer for which the coverage symbol BKN or OVC is reported. Significant convective clouds, when observed, are identified by addind the letters CB for (cumulonimbus) TCU for (towering cumulus) are reported in this grouping

17. EXAMPLE • The report would read: SCT020 SCT040 BKN080 OVC120 • 1stlayer at 2000 feet covers 2/8 = SCT • 2nd layer at 4000 feet covers 2/8 = (total of 4/8) SCT • 3rd layer at 8000 feet covers 1/8 = (total 5/8) BKN • 4th layer at 12000 feet covers 3/8 = (total 8/8 OVC

18. SKY CONDITION • cloud height and vertical visibility into a surface based layers are reported in 3-digits. • hundreds of feet up to 10,000 feet, thereafter in increments of 1,000 feet (All heights are “Above Ground level”). 030 = 3000 Feet 140 = 14000 Feet 003 = 300 Feet Example BKN080 = broken cloud at 8,000 ft VV008 = vertical visibility 800 ft

19. TEMPERATURE and DEWPOINT • observed values are rounded to the closest whole ºC with 0.5º rounded up to the next warmer degree; • “M” signifies a negative temperature; and • temperature and dew point are separated by a slash (/) • Example: 03/M01 • Temperature 3ºC / Dewpoint -1ºC

20. ALTIMETER SETTING • “A” is the group identifier that indicates altimeter setting • it is reported in inches of mercury • “A” Altimeter settings are given in hundredths of an inch of mercury. Example: A2937 = 29.37 inches of mercury • Some countries use “Q” grouping which indicates hectopascals; and Example: Q1013 = 1013 hectopascals

21. Recent Weather • “RE” identifies the group, followed,without a space, by the abbreviation for the applicable weather phenomena that was observed during the hour since the last METAR but not at the time of observation. • RE group may also be included in SPECI reports Example: REFZRA = recent freezing rain • RE -This group reports only recent weather of operational significance.

22. RECENT WEATHER • The following Phenomena may be reported as Recent Weather in a METAR/SPECI: freezing precipitation moderate or heavy rain/snow, ice pellets, hail, snow pellets moderate or heavy blowing snow sandstorm or dust-storm thunderstorm tornado, waterspout or funnel cloud volcanic ash, Note: The same phenomena will be reported in both the present weather and recent weather groups only if the phenomena was of greater intensity during the period since the last report.

23. RECENT WEATHER • Example: A moderate rainshower at 1800Z and a heavy rainshower at 1700Z. The 1800Z METAR would be reported as follows: SHRA for present Weather grouping ; and RERA in recent weather group implies recent heavy rainshowers

24. Wind Shear • Supplementary information on wind shear (up to 1600 ft AGL when provided by an aircraft on takeoff or approach path); and • “WS” identifier will be followed by a 2-digit group to indicate the runway number. The letters L, C, or R may be included if there are parallel runways at the airport . • WS All RWY - two or more runways. • Example: WS RWY 20R – Indicates wind shear was encountered on runway 20 right

25. REMARKS • The remarks grouping is identified by the indicator “RMK”. • Includes the following information: - cloud layer type and opacity in eights of sky concealed; - sea level pressure (SLP) in hectopascal (hPa); when first # of group is a 9 add 9 in front of pressure value, when first # is a 0 or 1 add 10 to front - other plain or abbreviated language comments significant to aviation. • Examples: • RMK SF5NS3 SLP134 – Indicates 5 oktas opacity stratus fractus, 3oktas opacity nimbostratus. SLP 1013.4 hPa. • RMK SC3 CI0 SLP992 - indicates 3 oktas opacity of stratocumulus, 0 opacity of cirrus. SLP 999.2 hPa

26. RMK -PARTIAL OBSCUREMENT • when an obscuring phenomena, such as fog, obscures a portion of the sky, it will not be reported in the Sky Condition grouping of the METAR, but will be shown in the RMK section. • however, the obstruction and the number of oktas it is concealing will be reported in RMK. • Example: the visibility is ½ SM in fog, which is obscuring 5/8 of the sky and no other cloud is present the METAR will show SKC in the Sky Condition groupings, and the remarks section will show FG5.

27. RMK – CLOUD ABBREVIATIONS • The following abbreviations are used for cloud types: • CI cirrus ST stratus • CS cirrostratus SF stratus fractus • CC cirrocumulus SC stratocumulus • AS altostratus CU cumulus • AC altocumulus CUFRA cumulus fractus • NS nimbostratus TCU towering cumulus • CB cumulonimbus ACC altocumulus castellanus

28. Confirmation Stage and Performance Check

29. Exercise For Class to Read • METAR CYTR 132000Z 12003KT 21/2SM BR OVC013 03/03 A2982 RMK SC8 SLP 023 • METAR CYYZ 132000Z 11003KT 1/8SM R06/1200FT/D -RADZ FG VV002 04/04 A2976 RMK FG8 SLP 001 • SPECI CYYZ 132035Z 12006KT 3SMBR OVC008 RMK ST8 • METAR CYYC 021600Z 05008KT 20SM FEW018 BKN057 OVC080 05/01 A2986 RMK SC2SC5AC1 SLP147