AMOSSG/5-SN No. 11

15/3/05

AERODROME METEOROLOGICAL OBSERVING SYSTEMS STUDY GROUP (AMOSSG)

FIFTH MEETING

Montreal, 11 to 14 April 2005

Agenda Item	6:	Aerodrome forecast requirements

USE OF 'PROB' IN TAF FORECAST

(Presented by W. Woveris)

SUMMARY
This paper outlines the user's views that "PROB" in TAF offer flexibility to the forecaster and operators and meet a user requirement.

1.	INTRODUCTION

1.1	The use of "PROB" in TAF has been questioned. There has not been much user complaint on the practice of including "PROB" in TAF to express the variability of weather and the probability of occurrence of a given phenomenon, such as thunderstorms. IATA favours the retention of the flexibility offered by the use of "PROB" during flight planning.

2.	DISCUSSION

2.1	IATA has a concern that some Meteorological Authorities were considering limiting the use of "PROB" in TAF. IATA is satisfied with the current provisions of Annex 3, Appendix 5, paragraphs 1.4 and 1.5. These recommendations still allow individual States to define their own procedures for probability groups, should they wish to do so.

3.	ACTION BY THE GROUP

3.1	The AMOSSG is invited to note the views of IATA expressed in this paper.

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