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AMOFSG/7-SN No. 11/ AMOFSG/7-SN No. 11
29/4/08
AERODROME METEOROLOGICAL OBSERVATION AND FORECAST STUDY GROUP (AMOFSG)
SEVENTH MEETING
Montréal, 9 to 12 September 2008
Agenda Item / 5: / Aerodrome observationsREPORTING OF RECENT WEATHER
(presented by Bill Maynard)
SUMMARYThis paper argues that the inclusion of recent weather as supplementary information in the METAR is superfluous when SPECI are provided. Itconcludes that Annex 3 should be revised to remove the recommendations regarding the inclusion of RE except for those sites where SPECI are not provided.
1.Introduction
1.1The Aerodrome Meteorological Observation and Forecast Study Group (AMOFSG) was established by the International Civil Aviation Organization (ICAO) Air Navigation Commission (ANC) to assist the Meteorology Secretary of the Air Navigation Bureau in reviewing the observation and forecasting Standards and Recommended Practices in Annex 3 — Meteorological Service for International Air Navigation. This study group is the successor to the Aerodrome Meteorological Observing Systems (AMOS) Study Group and has carried forward its work program with the addition of an explicitly wider scope to include forecasting topics.
1.2Recommendations in Annex 3 call for the inclusion of recent weather information as supplemental data in the METAR/SPECI. This practice may be superfluous in the presence of a continuous weather watch that issues SPECI promptly.
2.Discussion
2.1The inclusion of recent weather information as a supplemental component of the METAR/SPECI is covered in Annex 3 by a recommendation in Appendix 3 as follows:
4.8.1.1 Recommendation.— In local routine and special reports and in METAR and SPECI, the following recent weather phenomena, i.e. weather phenomena observed at the aerodrome during the period since the last issued routine report or last hour, whichever is the shorter, but not at the time of observation, should be reported, up to a maximum of three groups, in accordance with the templates shown in Tables A3-1 and A3-2, in the supplementary information:
— freezing precipitation
— moderate or heavy precipitation (including showers thereof)
— blowing snow
— duststorm, sandstorm
— thunderstorm
— funnel cloud (tornado or water spout)
— volcanic ash
2.2An effective and continuous weather watch program that issues SPECI promptly, when necessary, renders the inclusion of recent weather information redundant. A similar statement could be made regarding the inclusion of recent weather information in local routine reports where local special reports are issued promptly.
2.3It could be argued that recent weather information is necessary in the event that a SPECI is inadvertently missed and/or to provide an additional warning to pilots of the potential for hazardous weather conditions in the vicinity of the aerodrome. The latter possibility should be validated with operators.
3.Conclusion
3.1In the opinion of the author the resources used to encode recent weather where a SPECI program is in effect would be better directed to improving the SPECI program. In addition to SPECI, Pilots and others concerned with flight planning have access to a range of other meteorological information; such as weather radar, pilot reports, SIGWX forecast, area forecasts, TAF, SIGMET, AIRMET satellite images and lightning detection information to ensure they are aware of the existence of the specified recent weather conditions in the vicinity of the aerodrome.
3.2Consideration should be given to revising the Annex so that the recommendation to include supplemental information related to recent weather applies only to those sites where METAR are issued on a half-hourly basis as shown below:
4.8.1.1 Recommendation.— In local routine and special reports and in METAR issued on a half hourly basis and SPECI, the following recent weather phenomena, i.e. weather phenomena observed at the aerodrome during the period since the last issued routine report or last hour, whichever is the shorter, but not at the time of observation, should be reported, up to a maximum of three groups, in accordance with the templates shown in Tables A3-1 and A3-2, in the supplementary information:
— freezing precipitation
— moderate or heavy precipitation (including showers thereof)
— blowing snow
— duststorm, sandstorm
— thunderstorm
— funnel cloud (tornado or water spout)
— volcanic ash
4.Action by the Group
4.1The group is invited to:
a)review and comment upon the contents of this paper; and
b)agree with the conclusions stated in paragraphs 3.1 and 3.2.
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