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AVIATION 120

Today's Agenda. Aviation Special Weather Report (SPECI)Criteria for taking special weather reportsAWOS ObservationsDifferences from human observations. Aviation Special Weather Report (SPECI). SPECIs will be taken promptly to report changes which occur between scheduled transmission times, whenever one or more of the following elements has changed in the amount specified. The amount of change is with reference to the preceding routine or special observation.Ceiling: The ceiling decreases t9451

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AVIATION 120

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    1. AVIATION 120 Meteorology METAR CYZT 141700Z 00000KT 6SM +SHRA BR SCT015TCU BKN050 OVC075 12/11 A3018 RMK TCU4SC2AC2 SLP220= METAR CYZT 141800Z 26002KT 15SM SHRA FEW012 SCT030TCU BKN050 BKN075 13/12 A3018 RERA RMK CF1TCU2SC1AC1 SLP221= SPECI CYZT 141825Z 32009KT 15SM FEW012 FEW030TCU SCT050 SCT075 RMK CF1TCU2SC1AC1=

    2. Todays Agenda Aviation Special Weather Report (SPECI) Criteria for taking special weather reports AWOS Observations Differences from human observations

    3. Aviation Special Weather Report (SPECI) SPECIs will be taken promptly to report changes which occur between scheduled transmission times, whenever one or more of the following elements has changed in the amount specified. The amount of change is with reference to the preceding routine or special observation. Ceiling: The ceiling decreases to less than or increases to equal or exceed the following values of height: 1500 400* 100* 1000 300 Lowest published (IFR) minimum 500 200* * only applicable at aerodromes with a precision IFR approach such as an ILS or MLS

    4. Sky Condition: A layer aloft is observed below 1000 and no layer aloft was reported below this height in the previous observation. A layer aloft forms below the minimum for IFR straight in landing or takeoff and there was no layer reported in the previous observation. Visibility: Prevailing visibility decreases to less than or increases to equal or exceed: 3 SM SM 1 SM SM* 1 SM the lowest (IFR) published minimum * only applicable at aerodromes with a precision IFR approach such as an ILS or MLS Tornado, waterspout or funnel cloud: Is observed Disappears from sight Is reported by the public (reliable source) to have occurred within the preceding six hours and not previously reported by another station

    5. Thunderstorm: Begins Intensity increases to become heavy thunderstorm Ends (SPECI shall be made when 15 minutes have elapsed without the occurrence of thunderstorm activity) Precipitation: Hail begins or ends Freezing rain, freezing drizzle, or non-showery ice pellets begin, end or change intensity Rain, drizzle, snow, snow grains, snow pellets, showery ice pellets or ice crystals begin or end Specials shall be taken as required to report the beginning and ending of each individual type of precipitation, regardless of simultaneous occurrences of other types. A leeway of 15 minutes is allowed after the ending of precipitation before a SPECI is mandatory Changes in character of precipitation do not require a special if the break in precipitation does not exceed 15 minutes

    6. Wind: Speed (2-min mean) increases suddenly to at least double the previously reported value and exceeds 30 knots Direction changes sufficiently to fulfill criteria required for a wind shift NOTE: a wind shift is recorded when ALL of the following occur: Direction changes by 45 degrees or more Change occurs within 15 minutes Average speed at the completion of the wind shift is 10 KT or more Volcanic Eruption The occurrence of a volcanic eruption shall be reported by a special observation when observed. The following data will be included in the remarks section when known: Name of Volcano Direction (16 points true of compass) and approx. distance (SM) of the volcano Date/Time of eruption Height and direction of movement of ash cloud Other pertinent data EX: MT BLOWHARD VOLCANO 60MI WNW ERUPTED 091025 ASH CLOUD TO 300 MVG RPDLY SE

    7. Local Criteria The officer-in-charge may temporarily establish local criteria for special observations to meet local requirements. Must be approved by EC to become permanent Observers Initiative The criteria specified are MINIMUM requirements for taking special observations. In addition, any weather condition that, in the opinion of the observer is important for the safety and efficiency of aircraft operations or is otherwise significant, shall be reported by a special observation Canadian differences from ICAO SPECIs not issued for changes in RVR or Temperature changes SPECIs do not include temperature, dew point or altimeter settings, except from an automated site.

    8. SPECI EXAMPLES METAR CYIO 150200Z AUTO 25016KT 9SM OVC036 OVC059 01/M05 A2986 RMK SLP117= SPECI CYIO 150222Z AUTO 22012KT 9SM -SN BKN034 OVC057 00/M04 A2988= SPECI CYIO 150227Z AUTO 21013KT 9SM BKN034 OVC057 00/M04 A2988= METAR CYUB 150300Z 29012G17KT 10SM -SN BKN008 OVC220 01/M02 A3042 RMK SC5CI2 CIG ESTD SLP303= SPECI CYUB 150333Z 30013G18KT 10SM -SN SCT008 OVC030 RMK SC4SC4= METAR CYSM 150300Z 33009KT 15SM -DZ FEW007 OVC014 05/03 A2999 RMK SF2SC6 SLP166= SPECI CYSM 150319Z 33007KT 15SM OVC016 RMK SC8=

    9. AWOS Observations AWOS is capable of measuring (as a minimum): Cloud base height (up to 10 000 AGL) Sky cover (directly above the station) Visibility Temperature and Dew point* Wind velocity, direction and gusts* Altimeter setting (fail safe dual pressure sensors)* Precipitation occurrence, type, amount and intensity Occurrence of icing *Minimum sensors required for an LWIS LWIS report: LWIS CWDL 291700Z AUTO 25010G15KT 03/M02 A3017= AWOS differences to human observations Tend to produce more SPECIs due to unidirectional view, continuous sampling and precise measurements. (Lytton example on next slide) Review Observation Comparison Table in MET 3.15.5 of your AIM

    10. METAR CWLY 150200Z AUTO 00000KT 7SM -RA FEW001 BKN025 12/12 A3006 RMK PCPN 1.5MM PAST HR SLP182= SPECI CWLY 150222Z AUTO 00000KT 8SM -RA BKN020 12/12 A3006= SPECI CWLY 150224Z AUTO 00000KT 1 3/8SM -RA FEW001 OVC020 12/12 A3006 RMK VSBY VRBL 0.2V9.+= SPECI CWLY 150225Z AUTO 22002KT 1SM -RA BKN001 BKN020 OVC027 12/12 A3006 RMK VSBY VRBL 0.2V9.+= SPECI CWLY 150226Z AUTO 21003KT 5/8SM -RA BKN000 BKN020 OVC027 12/12 A3006 RMK VSBY VRBL 0.2V9.+= SPECI CWLY 150228Z AUTO 20003KT 3/8SM -RA OVC000 OVC020 OVC027 12/12 A3006 RMK VSBY VRBL 0.2V9.0= SPECI CWLY 150237Z AUTO 18009KT 3/4SM -RA FEW000 SCT020 OVC027 12/12 A3005 RMK VSBY VRBL 0.2V4.0= SPECI CWLY 150238Z AUTO 18010KT 1SM -RA SCT000 BKN020 OVC027 12/12 A3004 RMK VSBY VRBL 0.5V6.0= SPECI CWLY 150239Z AUTO 18009KT 2SM -RA BKN000 BKN020 OVC027 12/12 A3004 RMK VSBY VRBL 0.9V7.0= SPECI CWLY 150247Z AUTO 18010KT 2 1/2SM -RA FEW020 OVC027 12/11 A3004 RMK VSBY VRBL 2.5V9.+= SPECI CWLY 150251Z AUTO 18012KT 9SM -RA FEW020 BKN027 12/11 A3004= SPECI CWLY 150257Z AUTO 19006KT 9SM -RA BKN000 BKN020 OVC027 12/12 A3004= METAR CWLY 150300Z AUTO 19004KT 9SM -RA OVC000 OVC027 12/11 A3004 RMK PCPN 0.5MM PAST HR SLP177=

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