AMOSSG/5-SN No. 16

18/3/05

AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)

FIFTH MEETING

Montreal, 11 to 14 April 2005

Agenda Item	5:	Aerodrome observation requirements
5.1:	Reporting requirements and criteria

TS IDENTIFIED AS A PRESENT WEATHER PHENOMENA

(Presented by Dennis Hart)

SUMMARY
Edition 15 of ICAO Annex 3 introduced a difference between the described reporting practice for thunder/lightning and the supportive templates. This paper suggests changes to the templates to overcome the issue.

1.	INTRODUCTION

1.1	With the introduction of edition 15 of ICAO Annex 3 changes where incorporated in the templates for reporting local routine and special reports, METAR and SPECI. In case of the inclusion of characteristics of weather phenomena, the abbreviation TS was deleted out of the templates, compared with edition 14 of the annex. Furthermore, the abbreviation for the associated recent weather phenomena (RETS) was deleted.

1.2	While the templates do not allow the coding of the weather phenomena "thunder heard or lightning detected at the aerodrome but no observed precipitation", it is still included as a recommended practice to report. Appendix 3, paragraph 4.4.2.4 states this requirement in contradiction with the deletion out of the associated templates. This contradictions leads to misunderstanding and interpretation difficulties.

2.	DISCUSSION

2.1	Information on thunder and associated hazards is of importance for aeronautical users. It is still considered to be a requirement for (automated) observational reports; whether it is observed with or without precipitation. Consequently, it can be concluded that the reporting of heard thunder or detected lightning at the aerodrome but without observed precipitation(TS) in local routine and special reports, METAR and SPECI is still valid.

2.2	It is therefore proposed to harmonize the templates for local routine and special report, METAR and SPECI with the requirement stated in Appendix 3, paragraph 4.4.2.4; TS shall be reintroduced in the relevant templates to avoid misunderstanding and misinterpretation.

2.3	Consequently, the templates for reporting the for TS associated recent weather phenomena should be changed accordingly. The templates should be harmonized with Appendix 3, paragraph 4.8.1.1; RETS shall be reintroduced in the relevant templates.

3.	ACTION BY THE GROUP

3.1	The AMOSSG is invited to:

a)	note the content of this paper;

b)	agree on the proposal stated in paragraph 2.2;

c)	agree on the proposal stated in paragraph 2.3; and

d)	undertake any further action, if necessary.

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