AMOSSG/5-SN No. 15

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

REPORTING OF RECENT WEATHER PHENOMENA

(Presented by Dennis Hart)

SUMMARY
Edition 15 of ICAO Annex 3 introduced a difference between the described reporting practice for recent weather phenomena and the supportive templates. This paper suggest changes to overcome the issue.

1.	INTRODUCTION

1.1	During the implementation phase of edition 15 of ICAO Annex 3, KNMI was made aware of the differences between the recommendations and templates for reporting recent weather phenomena in local routine and local special report, METAR and SPECI.

1.2	The template for local routine and local special report and the template for METAR and SPECI recommend far more recent weather phenomena then is stated in the leading recommendation, especially for combinations with thunderstorms (RETS??). These differences lead to misunderstanding and interpretation difficulties.

2.	DISCUSSION

2.1	The templates, table A3-1 and table A3-2, clearly stipulate possible recent weather phenomena that should be reported. The listed possibilities for the different types of recent phenomena, precipitation in combination with thunderstorms, are in line with the reporting practice for different types of present thunderstorms that could be reported. And in line with the reporting practice for recent showers. These possible combinations of recent thunderstorms were introduced in the templates with the introduction of the 15th edition of ICAO Annex 3.

2.2	Unfortunately, the leading recommendation on the reporting of recent weather phenomena, Appendix 3, paragraph 4.8.1.1 only lists RETS as a phenomena.

2.3	It is therefore proposed to harmonize the recommendation on recent weather phenomena with the templates table A3-1 and table A3-2; RETSRA, RETSSN, RETSPL, RETSGR, RETSGS shall be introduced in the relevant paragraphs to avoid misunderstanding and misinterpretation.

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 2.3; and

c)	undertake any further action, if necessary.

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