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METWSG/2-SN No. 16
/ METWSG/2-SN No. 16
7/4/09

METEOROLOGICAL WARNINGS STUDY GROUP (METWSG)

SECOND MEETING

Montréal, 19 to 21 May 2009

Agenda Item / 5: / Content and issuance of SIGMET
5.4: / Use of closed lines of coordinates and location indicators to describe the area in SIGMET/AIRMET

PROPOSAL FOR CHANGES TO SIGMET FORMAT

(Presented by Sue O'Rourke)

SUMMARY
This study note discusses the proposal to amend the SIGMET format to allow an additional reference line at the end of the SIGMET message.

1.  INTRODUCTION

1.1  The Australian Bureau of Meteorology issues SIGMETs for the two Australian Flight Information Regions (FIR) which constitutes approximately 11 per cent of the globe.

1.2  Australian SIGMETs do not fully comply with ICAO Annex 3 — Meteorological Service for International Air Navigation standards and recommended practices. Two of the current registered differences are the use of a four-character sequence number and the use of a status line.

2.  SEQUENCE NUMBERS IN AUSTRALIAN SIGMETs

2.1  Given the extensive area of the Australian flight information regions (FIRs), they are divided into subdivisions for use in SIGMETs to ensure that air traffic management can quickly identify the region for which the SIGMET is valid (see Figures 1 and 2). The subdivision identifiers form part of a four-character sequence number instead of the ICAO standard of three characters.

For example:

YMMM SIGMET ME01 VALID 101200/101600 YMMM –

Instead of:

YMMM SIGMET A01 VALID 101200/101600 YMMM –

Figure 1: Sub-division Designators for Tropical Cyclone and Low-Level SIGMET

Figure 2: Sub-division Designators for Volcanic Ash and High-Level SIGMET

3.  SIGMET STATUS

3.1  In Australia, an additional line is added to the end of the SIGMET to alert the aviation industry, particularly air traffic management, to the relative status of the SIGMET. This is given by:

a)  STS:NEW ―- used when the SIGMET being issued is a new SIGMET for a new phenomenon or is a SIGMET being issued to correct a previously issued SIGMET which was in error (and has been cancelled).

b)  STS:REV ―- used when the phenomenon in an existing SIGMET (either NEW or REV) is expected to continue and the SIGMET is required to be reviewed.

c)  STS:CNL ―- used when a SIGMET is being cancelled.

3.2  The following examples highlight the use of the status line in Australian SIGMETs:

YMMM SIGMET ME01 VALID 101800/102200 YMMC-

YMMM MELBOURNE FIR SEV TURB FCST WI S3445 E12615 – S4030 E12145 – S4030 E12915 FL230/330 STNR NC

STS:NEW

YMMM SIGMET ME02 VALID 102200/110200 YMMC-

MELBOURNE FIR SEV TURB FCST WI S3445 E12615 - S4030 E12145 -

S4030 E12915 FL230/330 MOV SE 10KT WKN

STS:REV SIGMET ME01 101800/102200

YMMM SIGMET ME01 VALID 110045/110200 YMMCYMMM

MELBOURNE FIR CNL SIGMET ME01 102200/110200

STS:CNL SIGMET ME01 102200/110200

3.3  New sequence numbers for SIGMETs are required after 0000Z. The use of the status information also ensures that when the review or cancellation of a SIGMET occurs after 000Z, and refers to a SIGMET issued prior to 0000Z, that there is no confusion as to which previous SIGMET it is referring to.

4.  RECOMMENDATION

4.1  The current SIGMET format has serious shortcomings for large FIRs. The use of an additional information line would overcome many of these issues. The study group is invited to consider the benefits of using an additional line in the SIGMET message to include reference, when required, to:

a)  a specific subdivision of an FIR;

b)  the status of a SIGMET, i.e. NEW, REV or CNL; and

c)  SIGMET in adjoining FIR (when the weather phenomenon straddles an FIR).

4.2  An example of a SIGMET incorporating these recommendations in a Remark line might look like:

YMMM SIGMET C02 VALID 101800/102200 YMMC-

YMMM MELBOURNE FIR SEV TURB FCST WI S4030 E14515 – S4030 E15515 – S4330 E15315 – S4215 E14515 FL230/330 STNR NC

RMK ME REV C01 101400/101800 SEE ALSO YBBB C02

YBBB SIGMET C02 VALID 101800/102200 YMMC-

YBBB BRISBANE FIR SEV TURB FCST WI S4030 E14515 – S4030 E15515 – S4330 E15315 – S4215 E14515 FL230/330 STNR NC

RMK BS REV C01 101400/101800 SEE ALSO YMMM C02

5.  ACTION BY THE metwsg

5.1  The METWSG is invited to:

a)  note the information in this paper;

b)  consider the recommendation provided in Section 4.

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