AIRMET and ARFOR Changes...AIRMET and ARFOR Changes 1 This AIRMET and ARFOR User Guide defines the...

AIRMET and ARFOR Changes

A guide to the changes effective from 10th November 2016


Published by the Bureau of Meteorology

Version number/type Date of issue 1.0

17 Oct 2016

Approval for release: G.Jackson Head Aviation & Defence Meteorological Services 17 Oct 2016 © Commonwealth of Australia 2016 This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced without prior written permission from the Bureau of Meteorology. Requests and inquiries concerning reproduction and rights should be addressed to the Production Manager, Communication Section, Bureau of Meteorology, GPO Box 1289, Melbourne 3001. Information regarding requests for reproduction of material from the Bureau website can be found at www.bom.gov.au/other/copyright.shtml

http://www.bom.gov.au/other/copyright.shtml


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Table of Contents

1 Purpose ......................................................................................................................... 1

2 Introduction .................................................................................................................... 2

3 Key Changes ................................................................................................................. 3

3.1 Vertical Extent .................................................................................................................... 3 3.2 Comparison of current and new AIRMET requirements .................................................... 4 3.3 Format and validity period ................................................................................................. 4 3.3.1 Coding format .................................................................................................................... 4 3.3.2 Introduction of sequence number ...................................................................................... 4 3.3.3 Validity period and lead time ............................................................................................. 4 3.3.4 Remarks Line ..................................................................................................................... 4 3.3.5 Comparison of current and new AIRMET format .............................................................. 5

4 New AIRMET Criteria .................................................................................................... 7

5 New AIRMET Structure ................................................................................................. 8

5.1 Preamble ........................................................................................................................... 8 5.1.1 Location Indicator .............................................................................................................. 8 5.1.2 Message Identifier ............................................................................................................. 8 5.1.3 Sequence Number ............................................................................................................. 8 5.1.4 Validity period .................................................................................................................... 9 5.1.5 Issuing Office (or ICAO Location Indicator) ....................................................................... 9 5.2 Meteorological Information ..............................................................................................10 5.2.1 FIR (element 1) ................................................................................................................10 5.2.2 Phenomenon (element 2) ................................................................................................10 5.2.3 Phenomenon Observed or Forecast (element 3) ............................................................11 5.2.4 Location (element 4) ........................................................................................................11 5.2.5 Level (element 5) .............................................................................................................12 5.2.6 Movement (element 6) .....................................................................................................12 5.2.7 Intensity Change (element 7) ..........................................................................................12 5.3 Remark Information .........................................................................................................13

6 New AIRMET Cancellation .......................................................................................... 14

6.1 Cancellation Criteria ........................................................................................................14 6.2 Format..............................................................................................................................14 6.3 Additional Information ......................................................................................................14

7 New AIRMET Product Relationship ............................................................................. 15

7.1 Relationship to ARFOR ...................................................................................................15 7.2 Relationship to SIGMET ..................................................................................................15

8 New AIRMET Examples .............................................................................................. 16

8.1 Comparison of the current and new AIRMET format ......................................................16

9 Area Forecast (ARFOR) Changes ............................................................................... 19

9.1 New Australian Text ARFORs .........................................................................................19 9.1.1 Reporting cloud in New ARFOR ......................................................................................20 9.2 Medium-level Significant Weather Chart .........................................................................20 9.3 Grid Point Wind and Temperature Chart .........................................................................21 9.4 Obtaining Freezing Level Information ..............................................................................22

10 Appendix – Terms & Abbreviations .............................................................................. 24


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List of Tables

Table 1: Major differences between the Current AIRMET and the New AIRMET ........................ 4

Table 2: Examples of the current format compared to the new AIRMET format .......................... 6

Table 3: Criteria for issuance of AIRMET ...................................................................................... 7

Table 4: Issuing office (ICAO Location Indicator) .......................................................................... 9

Table 5: Meteorological Information contained with the AIRMET ................................................. 10

Table 6: Phenomena and abbreviations ........................................................................................ 11

Table 7: Level descriptions ............................................................................................................ 12

Table 8: Comparison of the current and new AIRMET format ...................................................... 17

Table 9: Examples of new AIRMET .............................................................................................. 18

Table 10: Cloud reporting in ARFORs ........................................................................................... 20

Table 11: GPWT Chart details ...................................................................................................... 21

List of Figures

Figure 1: Changes to vertical extent from current (left) to new (right) ........................................... 3

Figure 2: Current AIRMET format ................................................................................................. 5

Figure 3: New AIRMET format ...................................................................................................... 5

Figure 4: AIRMET Format ............................................................................................................. 8

Figure 5: Preamble ........................................................................................................................ 8

Figure 6: Example of an Area Forecast for AREA 40 (from 10 Nov 2016) ................................... 19

Figure 7: Example Mid-level SIGWX Chart ................................................................................... 21

Figure 8: Example GPWT Chart .................................................................................................... 22

Figure 9: Freezing Level on SIGWX chart..................................................................................... 23


1

This AIRMET and ARFOR User Guide defines the purpose of the AIRMET product and highlights the importance of AIRMETs to pilots and Air Traffic Control (ATC). This user guide provides detailed information on the upcoming changes to the ARFOR product, and the changes to AIRMET from the current AIRMET (mostly free text) product to the new International Civil Aviation Organization (ICAO) compliant AIRMET product. In addition to the changes to the product format and requirements, this document outlines the relationship between AIRMETs and ARFORs and SIGMETs.

1 Purpose


2

The Bureau of Meteorology (the Bureau) issues AIRMET advices to provide pilots with information on the occurrence and/or expected occurrence of certain hazardous meteorological phenomena below 10,000 feet that are not included within the valid low-level Area Forecast (ARFOR). AIRMET advices provide the relevant details of the hazard in a concise format and are complimentary to the routine issue and amendment of the ARFOR. AIRMET information is passed on to pilots by Air Traffic Control (ATC) by way of a Hazard Alert. The current format of the Australian AIRMET advice does not fully comply with ICAO Annex 3 requirements. Therefore, the Bureau will be introducing changes to its AIRMET format on the 10th November 2016 to align the AIRMET product with ICAO Annex 3 specifications. The new AIRMET will follow a very similar format to the existing SIGMET format. In addition, the Bureau plans to replace Australian text ARFORs with an ICAO compliant Graphical Area Forecast (GAF) product in November 2017. GAFs will not be amended, and therefore AIRMETs will be used for notifying users of specific changes to conditions not already contained in the relevant GAF.

2 Introduction


3

The following section summarises the key changes to AIRMETs and ARFORs, with the introduction of ICAO compliant AIRMETs.

3.1 Vertical Extent

AIRMET advices are related to the ARFOR. The introduction of ICAO compliant AIRMETs, which extend from the surface to 10,000 feet above mean sea level (AMSL)

1, will require the

vertical extent of ARFORs to also be reduced to 10,000 feet (see Figure 1 below). From the 10

th November 2016, the vertical extent of ARFORs and AIRMETs will be reduced to

10,000 feet (currently FL200). Weather information for airspace above 10,000 feet can be obtained from Medium and High Level Significant Weather (SIGWX) charts, Grid Point Wind and Temperature (GPWT) charts and the NAIPS Wind/Temperature Profile.

Figure 1: Changes to vertical extent from current (left) to new (right)

1 All heights are given in feet above mean sea level unless specifically stated otherwise

3 Key Changes


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3.2 Comparison of current and new AIRMET requirements

Table 1 below highlights the major differences between the current AIRMET and the new

AIRMET product.

3.3 Format and validity period

3.3.1 Coding format

Currently AIRMET advices are issued mostly using plain language. To align to ICAO coding format and to meet industry needs, the new AIRMET will use approved ICAO abbreviations. The AIRMET will be coded using similar coding to the SIGMET product.

3.3.2 Introduction of sequence number

The current AIRMET does not have a sequence number, instead it refers to the area forecast area number, e.g. Area 40. With the new AIRMET a sequence number will be introduced. The sequence number will be a two digit number which will provide a sequential count of the number of AIRMETs issued per FIR since 0001 UTC on the day concerned (Note: there is no alpha-character per phenomenon like SIGMETs);

3.3.3 Validity period and lead time

Currently an AIRMET has a period of validity that extends from the expected time of occurrence of the phenomenon to the expected time of its cessation, or to the end of the validity of the amended Area Forecast (to be issued after the AIRMET), whichever occurs first. New AIRMETs will have a maximum validity of 4 hours. AIRMETs will not be issued if the phenomenon is expected to commence more than four hours in the future, in this case the ARFOR will be amended without the issuance of an AIRMET.

3.3.4 Remarks Line

A remark (‘RMK’) line is included to list the identifiers of the ARFORs that are impacted by the AIRMET. In addition, 'SEE ALSO YXXX will be included when cross-referencing of AIRMET messages to any matching AIRMET in the neighbouring FIR is required.

Current AIRMET New AIRMET

Vertical coverage: Surface to FL200 Vertical coverage: Surface to 10,000 feet

Not cancelled but superseded by amendment of the ARFOR

Must be cancelled (following the amended ARFOR)

Validity can exceed 4 hours Maximum validity of 4 hours

When the wind at the lowest level forecast (e.g. 2000 FT) is expected to increase by at least 20 KT to at least 40 KT

Not required

Cumulonimbus or towering cumulus cloud not specifically mentioned

Isolated, occasional or frequent cumulonimbus or towering cumulus cloud

Table 1: Major differences between the Current AIRMET and the New AIRMET


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3.3.5 Comparison of current and new AIRMET format

Figure 2: Current AIRMET format

The new AIRMET format will follow the format defined in ICAO Annex 3, which is very similar to the SIGMET format. The differences between the current AIRMET format and new format are the inclusion of FIR details and the remark line. The criteria of issuance will meet ICAO requirements and is detailed in Section 4.

Figure 3: New AIRMET format

3.3.5.1 Additional Information

In addition to ICAO specification, AIRMETs will have the following procedural/format requirements:

1. AIRMETs will not be issued to notify of improvements to weather on an ARFOR, an amended ARFOR will be issued to notify of improvements (same as current practice);

2. AIRMETs can be issued per ARFOR (like current ARFOR practice) or per phenomenon, which could be across ARFORs and/or FIRs, (an AIRMET will be issued for each affected FIR) similar to SIGMETs;

3. There is no provision for amendments to AIRMET and therefore if an amendment is required or an error is to be corrected, the current AIRMET will be cancelled, and a new AIRMET issued with a new number; and

4. AIRMET are not required to be issued during those periods when an ARFOR is not valid for the relevant area.


6

3.3.5.2 Examples of the current and new AIRMET


AIRMET for fog

AIRMET 231400Z AREA 21 VALID 231400/232300 FOG FORECAST WITH VISIBILITY BELOW 1000M FROM 1400Z E RANGES. AMEND AREA FORECAST FOLLOWS

YMMM AIRMET 01 VALID 231400/231800 YSRF – YMMM MELBOURNE FIR SFC VIS 0300M (FG) FCST WI YORG – KIAN – YBOM – YSCN SFC/0600FT STNR NC RMK: AREA 21

AIRMET for Thunderstorm

AIRMET 190530Z AREA 52 VALID 190530/190930 THUNDERSTORMS OBSERVED AT 0525Z WITHIN AREA YCFH TO YMRE TO YCBP TO YALA SFC/FL400 MOV S 05KT NC. AMEND AREA FORECAST FOLLOWS.

YMMM AIRMET 02 VALID 190530/190930 YPRM – YMMM MELBOURNE FIR ISOL TS OBS AT 0525Z WI YCFH - MRE - YCBP - YALA TOP ABV 10000FT MOV S 05KT NC RMK: AREA 52

Table 2: Examples of the current format compared to the new AIRMET format


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AIRMET will be issued for the following phenomena if not already contained in the current

ARFOR:

Weather element / phenomenon

Criteria

Visibility Widespread areas of visibility of less than 8 KM

Cloud

Widespread areas of cloud coverage of BKN or OVC below 1500 FT above ground level; and

Isolated, occasional or frequent cumulonimbus or towering cumulus cloud. (See notes below)

Weather

Thunderstorms – isolated and occasional (with or without hail);

Moderate icing (not issued separately when icing occurs in convective clouds);

Moderate turbulence (not issued separately when turbulence occurs in convective clouds);and

Moderate mountain waves

Table 3: Criteria for issuance of AIRMET

Notes:

1. AIRMETs will not be issued for wind.

2. Definitions:

Widespread indicates greater than 75% coverage or more of an area of 3000

NM2 or more.

Isolated if it consists of individual features which affect, or are forecast to affect,

an area with a spatial coverage of up to 50% of an area of 3000 NM2 or more.

Occasional if it consists of well separated features which affect, or are forecast to

affect, an area with a spatial coverage greater than 50% but not more than 75%

of an area of 3000 NM2 or more.

Frequent if it consists of features with little or no separation which affect, or are

forecast to affect, an area with a spatial coverage greater than 75% of an area of

3000 NM2 or more.

3. If lightning, thunder or hail is expected the phenomenon TS will be used.

4. The phenomena CB or TCU will only be used when not accompanied by lightning,

thunder or hail.

5. Turbulence and Icing will not be used in connection with convective clouds as they are

implied.

4 New AIRMET Criteria


8

AIRMET messages are issued in the format defined in the following paragraphs, and are comprised of the following three sections:

a) Preamble, b) Meteorological Information, and c) Remarks Information.

Figure 4: AIRMET Format

Note: See Section 6 for information regarding the format of cancellation AIRMETs.

5.1 Preamble

The preamble comprises

5.1.1 Location Indicator

The preamble commences with the ICAO location indicator of the Australian Flight Information Region i.e. either YMMM (Melbourne FIR) or YBBB (Brisbane FIR), for which AIRMET is issued.

5.1.2 Message Identifier

The message identifier is “AIRMET”

5.1.3 Sequence Number

5 New AIRMET Structure

Figure 5: Preamble


9

A two-digit sequence number provides a sequential count of the number of AIRMETs issued within an FIR since the last 0001 UTC day, commencing at 01. The sequence number will reset to 01 on the UTC day rollover (at 0001 UTC). For example if an AIRMET issued at 2200 UTC was allocated sequence number 08, and the next AIRMET issued for the FIR was at 0015 UTC it would be allocated sequence number as 01. Note: The above is different to the changes to SIGMET sequence number. From 10

th

November 2016 the Australian SIGMET sequence numbers will no longer reset at 0001UTC, and instead the sequence numbering will continue until the SIGMET for the event is cancelled. Should more than 99 SIGMETs be issued for a particular event, the number portion of the sequence number will go from 99 to 02. Sequence number 01 is will be reserved for new SIGMETs.

5.1.4 Validity period

The validity period is given in the format DDHHMM/DDHHMM, where DD is the day of the month and HHMM is the time in hours and minutes in UTC. AIRMET will have a maximum validity period of 4 hours.

5.1.5 Issuing Office (or ICAO Location Indicator)

The issuing office gives the ICAO indicator for the Bureau office issuing the AIRMET, i.e. one of the locations listed in the following table:

Location Indicator

Adelaide YPRM

Brisbane YBRF

Darwin YPDM

Hobart YMHF

Melbourne YMRF

Sydney YSRF

Perth YPRF

Table 4: Issuing office (ICAO Location Indicator)

The ICAO location indicator is always followed by a hyphen “-” without a space, to separate the preamble from meteorological information.


10

5.2 Meteorological Information

The meteorological information part of an AIRMET consists of the elements (1 to 7) indicated in

Table 5 Table 5: Meteorological Information contained with the AIRMETbelow.

Note: The square brackets "[ ]" indicate the element is optional or conditional and "< >" means variable elements.

1

2 3 4

Name of the FIR Phenomenon Observed or forecast

Location

Location indicator and name of the FIR

Description of phenomenon

Indication whether the information is observed and expected to continue, or forecast

Geographical forecast location of the phenomenon

5

6 7

Level Movement or expected movement

Change in intensity

Vertical Extent Movement or expected movement (direction and speed)

Expected changes in intensity

Example: YMMM MELBOURNE FIR ISOL TS OBS AT 0525Z WI YCFH - YMRE - YCBP - YALA TOP ABV 10000FT MOV S 05KT NC

Table 5: Meteorological Information contained with the AIRMET

5.2.1 FIR (element 1)

FIR is given using the indicator (CCCC) name and FIR, for example, YBBB BRISBANE FIR or YMMM MELBOURNE FIR.

5.2.2 Phenomenon (element 2)

The description of the phenomenon is given in Table 6 below. AIRMET will be issued as per the

criteria in Table 3.

Phenomenon Abbreviation Example

Widespread areas affected by a reduction of visibility of less than 8 KM (including the weather causing the visibility reduction)

SFC VIS nnnnM (nn)

Where (nn) is one of the following weather phenomena or combinations thereof: BR, DS, DU, DZ, FC, FG, FU, GR, GS, HZ, PL, PO, RA, SA, SG, SN, SQ, SS or VA

SFC VIS 0300M (FG) SFC VIS 1500M (BR)

Widespread areas of broken or overcast cloud with height of base less than 1500 FT above ground level (all cloud heights reported AMSL)

BKN CLD [n]nnn/[ABV] [n]nnnnFT

BKN CLD 500/2000FT BKN CLD 2000/ABV10000FT BKN CLD 4000/8000FT

OVC CLD [n]nnn/[ABV] OVC CLD 500/2000FT


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[n]nnnnFT

OVC CLD 4000/ABV10000FT OVC CLD 4000/8000FT

Towering Cumulus cloud ISOL TCU OCNL TCU FRQ TCU

ISOL TCU OCNL TCU FRQ TCU

Cumulonimbus Cloud ISOL CB OCNL CB FRQ CB

ISOL CB OCNL CB FRQ CB

Thunderstorms – isolated and occasional (with or without hail);

ISOL TS[GR] ISOL TS ISOL TSGR

OCNL TS[GR] OCNL TS OCNL TSGR

Moderate Turbulence* MOD TURB MOD TURB

Moderate Icing* MOD ICE MOD ICE

Moderate Mountain Waves MOD MTW MOD MTW

* not issued separately when icing or turbulence occurs in convective clouds

Table 6: Phenomena and abbreviations

5.2.3 Phenomenon Observed or Forecast (element 3)

Type of information, observed or forecast, is given using one of the following: Observed (OBS): When the exact time of the observation is known, OBS is followed by the time group AT

GGggZ. If the exact time of the observation is not known, the time is not included The use of “OBS” occurs if either:

o there has been a recent report of the phenomenon; or o there is strong recent meteorological evidence such as on remote sensing imagery or

RADAR which leads the forecaster to believe that the phenomenon is occurring.

Forecast (FCST): When FCST is used, the time of commencement of the phenomenon is the beginning of

the validity period. The use of “FCST” is used when a phenomenon is expected to occur (forecast event). In

other words, the phenomenon is not observed but there is strong meteorological evidence (i.e. model guidance) to suggest that the phenomenon will be occurring within the prescribed forecast time.

It should be noted that if the phenomenon is forecast with a lead time of more than 4 hours then no AIRMET will be issued but the ARFOR will be amended.

5.2.4 Location (element 4)

The location of the phenomenon is the location of the phenomenon at the beginning of the validity period. The location of the phenomenon can be depicted as a single location, where <CCCC> is an approved PCA location or it can be depicted as an area bounded by a series of PCA locations and/or coordinate points.


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5.2.5 Level (element 5)

The vertical extent of the phenomenon is given in a format similar to that used in SIGMET messages. The vertical extent will be the lowest and highest altitude of the phenomenon during the full validity period. Vertical extent is given in feet (FT). Feet are used for levels at and below 10,000 feet. If a layer is extending through the transition level (10,000 feet) then: Where the base of the phenomenon is below 10,000 feet but the top is above 10,000 feet,

ABV nnnnFT is used, where 'nnnn' is the base of the phenomenon, e.g. ABV 5000FT.

In the case of TS, CB and TCU where top of the phenomenon may be above 10,000 feet then TOP ABV10000FT shall be used.

Description Format Example

Reporting a layer where the base and top are at or below 10,000 feet

[SFC/][n]nnnnFT) or [n]nnnnFT or [n]nnnn/[n]nnnnFT)

SFC/7000FT 5000FT 6000/10000FT 2000/8000FT

Reporting a layer (except for TS, CB and TCU) where the base is below 10,000 feet, but the top is above 10,000 feet

ABV nnnnFT ABV 5000FT

Reporting TS, CB and TCU where the base is below 10000 feet

TOP [n]nnnnFT when the top is at or below 10,000 feet or TOP ABV[n]nnnnFT when the top is above 10,000 feet

TOP 10000FT TOP 8000FT

TOP ABV10000FT

Reporting TCU, CB and TS where both base and top are above 10,000 feet

ABV [n]nnnnFT ABV 10000FT

Table 7: Level descriptions

Square brackets “[ ]” indicate that element 5 is optional. Specifically, element 5 is not required when AIRMET is issued for widespread BKN or

OVC cloud as the levels are already reported immediately after the phenomenon cloud, as per Table 6.

For example: YMMM MELBOURNE FIR BKN CLD 4000/8000FT OBS WI YSPE - TBL - LOSKU - CRAVN - CORKY - MTB - SOFAL - YXMW - MUI - YWCH - YGLI STNR NC

5.2.6 Movement (element 6)

The movement or expected movement is given with reference to one of the 16 compass radials and the speed is given in knots (KT), for example MOV NNE 25KT. Speed must be in 5 KT increments and two digits shall be used for speeds less than 10 KT. The abbreviation STNR (stationary) is used if no significant movement is expected.

5.2.7 Intensity Change (element 7)

The expected evolution of the phenomenon’s intensity is indicated by one of the following abbreviations:

INTSF: intensifying


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WKN: weakening NC: no change

5.3 Remark Information

The remark (RMK) is found only in the Australian AIRMET message and is removed before sending internationally. It begins on a new line. The purpose of the remark line is to allow additional information to be conveyed in an AIRMET message, such as:

list of ARFOR identifiers the AIRMET message applies to; and/or cross-referencing AIRMET messages when a phenomenon straddles the FIR

boundary; For example, the AIRMET messages below cross reference AIRMETs in neighbouring FIRs: AIRMET for Melbourne FIR: YMMM AIRMET 01 VALID 230800/231200 YSRF - YMMM MELBOURNE FIR MOD TURB FCST WI YCTM – YBIA – YGFN – YSNW SFC/8000FT MOV E 05KT NC RMK: AREA 20, 21 SEE ALSO YBBB 01 AIRMET for Brisbane FIR: YBBB AIRMET 01 VALID 230800/231200 YSRF - YBBB BRISBANE FIR MOD TURB FCST WI YCTM – YBIA – YGFN – YSNW SFC/8000FT MOV E 05KT NC RMK: AREA 20, 21 SEE ALSO YMMM 01


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6.1 Cancellation Criteria

Currently AIRMETs are not cancelled but are superseded by the amendment or routine issue of

the relevant ARFOR. To comply with ICAO requirements, all AIRMETs will be cancelled.

An AIRMET will be cancelled when during the validity period of an AIRMET the phenomenon for

which the AIRMET had been issued is included in an amended ARFOR(s). The following will be

performed in sequential order:

Issue an AIRMET; Amend ARFOR(s); and then Cancel AIRMET.

Note: There is no provision for amendments to AIRMET and therefore if an amendment is

required or an error is to be corrected the current AIRMET will be cancelled, and a new AIRMET

issued with the next sequence number.

6.2 Format

The 'Preamble' and 'Remarks Line' (as in Section 5) of a cancelled AIRMET remain the same

as for an AIRMET. However, the meteorological information of a cancelled AIRMET changes

slightly.

The abbreviation CNL is included to refer to cancellation, and the remaining elements match

those of the AIRMET that is to be cancelled, the format is as follows:

<CCCC> AIRMET <nn> VALID < YYGGgg/YYGGgg> <issuing office>-

<CCCC><FIR name> FIR CNL AIRMET<nn> < YYGGgg/YYGGgg>

RMK

For example:

YMMM AIRMET 04 VALID 190830/190930 YPRM –

YMMM MELBOURNE FIR CNL AIRMET 02 190530/190930

RMK: AREA 52

6.3 Additional Information

If an AIRMET is cancelled, it is cancelled for all affected ARFORs. AIRMETs will not be

cancelled until all associated ARFORs are amended.

A cancelling AIRMET is only issued with immediate effect (i.e. it should not be issued with effect

in the future) and is to be given validity for the full remaining period of the AIRMET it cancels.

6 New AIRMET Cancellation


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7.1 Relationship to ARFOR

An AIRMET is issued to advise pilots of the occurrence or expected occurrence of specified

weather phenomena which may affect the safety of aircraft operations, which were not already

included in the valid ARFOR. If the phenomenon is included in the ARFOR, then there is no

requirement to issue an AIRMET.

Once the AIRMET is issued, an amended ARFOR that includes the AIRMET phenomenon will

be issued and then the AIRMET will be cancelled.

7.2 Relationship to SIGMET

A SIGMET is always issued for its specified weather phenomena. On the other hand, an

AIRMET is issued for its specified weather phenomena if not included in the currently valid

ARFOR.

In a situation where a phenomenon described in a SIGMET decreases in intensity to now meet

the AIRMET criteria (e.g. SEV TURB becomes MOD TURB), the SIGMET shall then be

cancelled. An AIRMET shall be issued, only if the phenomenon (MOD TURB) was not forecast

in the current ARFOR.

Conversely, a phenomenon that had resulted in the issuance of an AIRMET may increase in

intensity to the SIGMET criteria. In this situation, a SIGMET will be issued followed by a

cancelled AIRMET

7 New AIRMET Product Relationship


16

8.1 Comparison of the current and new AIRMET format

8 New AIRMET Examples


Example 1: AIRMET for Fog

AIRMET 231400Z AREA 21 VALID 231400/232300 FOG FORECAST WITH VISIBILITY BELOW 1000M FROM 1400Z E RANGES. AMEND AREA FORECAST FOLLOWS.

YMMM AIRMET 01 VALID 231400/231800 YSRF – YMMM MELBOURNE FIR SFC VIS 0300M (FG) FCST WI YORG – KIAN – YBOM – YSCN SFC/0600FT STNR NC RMK: AREA 21

Example 2: AIRMET for Thunderstorms

AIRMET 190530Z AREA 52 VALID 190530/190930 THUNDERSTORMS OBSERVED AT 0525Z WITHIN AREA YCFH TO YMRE TO YCBP TO YALA SFC/FL400 MOV S 05KT NC. AMEND AREA FORECAST FOLLOWS.

YMMM AIRMET 02 VALID 190530/190930 YPRM – YMMM MELBOURNE FIR ISOL TS OBS AT 0525Z WI YCFH - YMRE - YCBP - YALA TOP ABV 10000FT MOV S 05KT NC RMK: AREA 52

Example 3 - AIRMET for turbulence affecting two FIRs –

AIRMET for AREA 20:

AIRMET 230300Z AREA 20 VALID 230800/231200 MOD TURB FORECAST FROM 0330Z WITHIN AREA YORG TO YBIA TO YGFN TO YSBK SFC/FL080 MOV E 05KT NC. AMEND AREA FORECAST FOLLOWS.

AIRMET for AREA 21:

AIRMET 230300Z AREA 21 VALID 230800/231200 MOD TURB FORECAST FROM 0330Z WITHIN AREA YCTM TO YORG TO YSBK TO YSNW SFC/FL080 MOV E 05KT NC. AMEND AREA FORECAST FOLLOWS.

AIRMET for Melbourne FIR:

YMMM AIRMET 06 VALID 230800/231200 YSRF – YMMM MELBOURNE FIR MOD TURB FCST WI YCTM – YBIA – YGFN – YSNW SFC/8000FT MOV E 05KT NC RMK: AREA 20, 21 SEE ALSO YBBB 10

AIRMET for Brisbane FIR:

YBBB AIRMET 10 VALID 230800/231200 YSRF – YBBB BRISBANE FIR MOD TURB FCST WI YCTM – YBIA – YGFN – YSNW SFC/8000FT MOV E 05KT NC RMK: AREA 20, 21 SEE ALSO YMMM 06


17

Examples of new AIRMET for various phenomena

AIRMET for Widespread areas affected by reduction of visibility due to dust

WAAU21 ASRF 230350

YMMM AIRMET 01 VALID 231400/231800 YSRF –

YMMM MELBOURNE FIR SFC VIS 1000M (DU) FCST WI YORG – KIAN – YBOM – YSCN

SFC/3000FT STNR NC

RMK: AREA 21

AIRMET for widespread areas of broken cloud

WAAU21 AMRF 230355

YMMM AIRMET 02 VALID 230409/230809 YMRF-

YMMM MELBOURNE FIR BKN CLD 4000/8000FT FCST WI YSPE - TBL - CRAVN - MTB -

SOFAL - YWCH - STNR NC

RMK: AREA 40, 20

AIRMET for occasional cumulonimbus cloud

WAAU21 AMRF 230400

YMMM AIRMET 02 VALID 230409/230809 YMRF-

YMMM MELBOURNE FIR OCNL CB FCST WI YWWL – YMRY-S3730 E15100 – YMCO -

YMAY TOP ABV10000FT STNR NC

RMK: AREA 21, 22, 30/32

AIRMET for isolated thunderstorms

YMMM AIRMET 02 VALID 190530/190830 YPRM –

YMMM MELBOURNE FIR ISOL TS OBS AT 0525Z WI YCFH - YMRE - YCBP - YALA TOP

ABV10000FT MOV S 05KT NC

RMK: AREA 52

AIRMET for moderate mountain waves

WAAU21 AMHF 230355

YMMM AIRMET 03 VALID 230510/230910 YMHF-

YMMM MELBOURNE FIR MOD MTW OBS AT 0505Z WI YWYY – S4000 E15000 –S4300

E14900 - YMSY ABV 5000FT STNR NC

RMK: AREA 70

AIRMET for moderate turbulence

WAAU21 ASRF 100430

YMMM AIRMET 09 VALID 100500/100900 YSRF-

YMMM MELBOURNE FIR MOD TURB FCST WI YORG - S3500 E15230 - S3730 E15100 -

YMCO - YCOM SFC/8000FT STNR NC

Example 4 - Cancel AIRMET for Example 2 above

AIRMETs currently not cancelled but superseded by an amended ARFOR.

YMMM AIRMET 07 VALID 190830/190930 YPRM – YMMM MELBOURNE FIR CNL AIRMET 02 190530/190930 RMK: AREA 52

Table 8: Comparison of the current and new AIRMET format


18

RMK: AREA 21

AIRMET for Moderate Icing

WAAU21 ABRF 100430

YBBBB AIRMET 11 VALID 100500/100900 YBRF-

YBBB BRISBANE FIR MOD ICE FCST WI YBRK – S2330 E15230 - YSPE – S2845 E15500 –

S3400 E15230 – YORG - ABV 8000FT STNR NC

RMK: AREA 20, 40

Table 9: Examples of new AIRMET


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9.1 New Australian Text ARFORs

The vertical extent of ARFORs will be reduced to 10,000 feet (from FL200). Weather information for airspace above 10,000 feet can be obtained from Significant Weather (SIGWX) and Grid Point Wind and Temperature (GPWT) charts and the NAIPS Wind/Temperature Profile.

9 Area Forecast (ARFOR) Changes

AREA FORECAST 082300 TO 091100 AREA 40 OVERVIEW: SHOWERS AND THUNDERSTORMS DEVELOPING S OF YBBN/S2715 E14930 FROM 02Z. SUBDIVISIONS: A: N OF YBBN/S2715 E14930 B: S OF YBBN/S2715 E14930 WIND: 2000 5000 7000 10000 A: 280/15 290/15 280/10 300/15 MS01 B: 330/25 320/30 310/30 300/35 MS04 CLOUD: A: SCT CU 3000/8000 WITHIN 60NM OF COAST. B: ISOL CB 4000/45000 FROM 02Z. OCNL TCU 4000/24000. BKN ST 0500/5000 IN TS, SCT IN SHRA. WEATHER: A: NIL SIGNIFICANT B: +TSRA, -SHRA VISIBILITY: A: UNRESTRICTED B: 1000M IN +TSRA, 6KM IN -SHRA FREEZING LEVEL: A: 9500 FT B: 8500 FT ICING: SEV IN CB AND TCU ABV FZLVL TURBULENCE: SEV IN CB AND TCU MOD IN CU REMARKS: FOR CLARIFICATION OF METEOROLOGICAL ISSUES CALL 07 3229 1854.

Figure 6: Example of an Area Forecast for AREA 40 (from 10 Nov 2016)


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9.1.1 Reporting cloud in New ARFOR

Cloud will be reported as per Table 10 below:

If base and top below 10000FT

If base below 10000FT and top above 10000FT

If base and top above 10000FT

Reporting TCU and CB

2000/10000 with ISOL TCU tops to 25000FT

2000/45000 12000/45000 (base and top always reported)

Reporting cloud below 10000FT AMSL

3000/7000 5000/ABV 10000FT n/a

Reporting cloud producing precipitation

2000/9000 8000/ABV 10000FT ABV 10000FT

Table 10: Cloud reporting in ARFORs

9.2 Medium-level Significant Weather Chart

Weather information for the airspace between10,000 feet AMSL and FL200 will not be contained in ARFORs, instead this information should be obtained from the Medium-level SIGWX chart or SIGWX Medium (SWM). SWM provides weather information for airspace from FL100 to FL250 and these charts are valid for 00, 06, 12 and 18 UTC. SWM are normally first available fifteen hours before validity, and will be updated four hours before validity. SWM charts are valid for the time point indicated (00, 06, 12 or 18 UTC) but are used for operations within three hours each side of this time. The following phenomena are shown on the charts:

tropical cyclones

moderate or severe turbulence, including clear air turbulence (CAT)

moderate or severe icing

surface fronts

cumulonimbus (CB) cloud associated with thunderstorms and with any of the above

non-convective cloud associated with in-cloud moderate or severe turbulence or icing

jet streams

volcanic eruptions

tropopause heights

radioactive material

Note: On SIGWX charts the inclusion of CB should be understood to include all weather phenomena associated with cumulonimbus, i.e. thunderstorms, moderate or severe icing, moderate or severe turbulence, and hail.

For more information on SIGWX charts, refer to Significant Weather (SIGWX) Charts brochure

available from the Bureau’s aviation Knowledge Centre at:

http://www.bom.gov.au/aviation/data/education/sigwx.pdf

http://www.bom.gov.au/aviation/data/education/sigwx.pdf


21

Figure 7: Example Mid-level SIGWX Chart

9.3 Grid Point Wind and Temperature Chart

Currently, ARFORs have a section for wind and temperature information covering up to FL185. Wind and temperature information at FL140 and FL185 will not be contained in the ARFOR from 10 Nov 2016. Instead this information should be obtained from Grid Point Wind and Temperature (GPWT) charts. The GPWT chart provides a text-based display of forecast wind and temperature data for multiple levels. The Bureau currently produces Mid-level (FL050 to FL240) and High-level GPWT (FL180 to FL450) charts for various regions. In addition, the Bureau has commenced producing a national Low-level GPWT chart providing the wind and temperature information from 1000 feet to FL140. Table 11 outlines the areas of coverage and vertical extent of the various GPWT charts.

Level Region Time

Low-level (1000 feet - FL140)

Australia 00Z, 03Z, 06Z, 09Z, 12Z, 15Z, 18Z, 21Z

Mid-level (FL050-240)

Australia 00Z, 06Z, 12Z, 18Z

NE

SE

TAS

WEST

High-level (FL180-450)

Australia 00Z, 06Z, 12Z, 18Z

Tasman regions

Table 11: GPWT Chart details


22

For more information on GPWT charts, refer to Grid Point Wind Forecasts brochure available at

http://www.bom.gov.au/aviation/data/education/gridpoint.pdf

Figure 8: Example GPWT Chart

9.4 Obtaining Freezing Level Information

If the freezing level on the ARFOR is indicated as above 10,000 feet (ABV 10000FT), the zero degree isotherm or freezing level can be obtained from the GPWT chart or from the Medium-level SIGWX chart as indicated in Figure 9 below.

http://www.bom.gov.au/aviation/data/education/gridpoint.pdf


23

Figure 9: Freezing Level on SIGWX chart


24

The following list includes the terms and abbreviations approved for use in Area Forecasts and

AIRMETs. Abbreviations as per the current PCA chart and/or coordinates are also approved for use in

AIRMET and ARFORs.

Note: The abbreviations provided in the list below are for general use in ARFORs. In AIRMETs, only

the required ICAO abbreviations will be included.

Approved term Abbreviation Description/Use Example

Above ABV Above a level FZLVL ABV 10000FT

Altocumulus AC Cloud type

Altostratus AS Cloud type

Amend AMD Header and section

heading

Anticlockwise Used for description of

winds

WINDS ALL LEVELS

TENDING 30 DEGREES

ANTICLOCKWISE AFTER 12Z

At AT At a time or location TROUGH

YREN/YMMB/CHOMP AT 17Z

Becoming BECMG For temporal changes SCATTERED SHOWERS

BECOMING ISOLATED

AFTER 10Z

Below BLW Below a level MOD TURB BLW 5000FT

Between For geographic description

only, not vertical

ISOLATED SHOWERS

BETWEEN

KOOM/FOWB/YPAG AND

IVPEM/ISLAV/PNE

Blowing BL Weather descriptor

Blowing dust BLDU Weather phenomenon

Blowing sand BLSA Weather phenomenon

Blowing snow BLSN Weather phenomenon

Broken BKN Cloud amount

10 Appendix – Terms & Abbreviations


25

Calm Wind description

Centre For use with low, tropical

low or tropical cyclone

WI 100NM of TC CENTRE

Clearing For temporal changes ISOLATED SHOWERS,

CLEARING FROM 12Z

Clockwise Used for description of

winds

WINDS CLOCKWISE WI

125NM OF TROPICAL LOW

Cloud Section heading of Area

forecast or general cloud

description

ICING: MOD IN CLOUD ABV

FZLVL

Cloud base BASE Description of base of cloud BASE TENDING 3000 MORE

THAN 60NM INLAND

Cloud on ground Limited to critical locations BKN ST 2300 [CLOUD ON

GROUND]

Cloud top TOP/S Description of cloud top TOPS ABV 10000FT NE OF

YGEL/YMDN

Coast At the coast. If using to

describe an area a distance

must be given.

BKN ST 0500/2000

COAST/30NM INLAND

Contracting Geographical changes THUNDERSTORMS

CONTRACTING TO N OF

YYND/YTNK/YKLN

BY 03Z

Cooler/Colder Used for description of

temperatures

TEMPERATURE 8 DEGREES

COOLER S OF PEAR/PNE

Cumulonimbus CB Cloud type

Cumulus CU Cloud type

Decreasing Changes in height CLOUD BASE DECREASING

TO 800FT AFTER 14Z

Degree/s DEG/DEGS Used for description of

temperatures

Developing For temporal changes SCATTERED FOGS

DEVELOPING AFTER 11Z

Drifting dust DRDU Weather phenomenon

Drifting snow DRSN Weather phenomenon


26

Drizzle DZ Weather phenomenon

Dust DU Weather phenomenon

Dust/sand whirls

(dust devils)

PO Weather phenomenon

Dust Storm DS Weather phenomenon

East E Direction E OF YBRK/YTFD

Embedded EMBD Weather and cloud

description

Extending EXTD Geographical change EXTENDING TO SE OF

YMER/YLTV/YMAV/YCTY

AFTER 10Z

Falling Limited to overview SCATTERED SHOWERS,

FALLING AS SNOW ABOVE

5000FT

AFTER 08Z

Feet FT Height description

Few FEW Cloud type

Flight level FL Height description

Fog FG Weather phenomenon

Freezing drizzle FZDZ Weather phenomenon

Freezing fog FZFG Weather phenomenon

Freezing level FZLVL Freezing level description ICING: MOD IN CU ABV

FZLVL

Freezing rain FZRA Weather phenomenon

Frequent FRQ Weather and cloud amount

description

From FM Temporal changes

Front Synoptic feature FRONT YREN/YMMB/CHOMP

AT 17Z

Funnel cloud FC Weather phenomenon

Hail GR Weather phenomenon


27

Haze HZ Weather phenomenon

Heavy + Weather intensity

Hills Use to be minimised and

only used when specific

location can be used

Icing Section heading of Area

forecast and weather

phenomenon

In Used for describing cloud ST 0500/2000 IN SHRA.

Increasing For use with winds

Inland Distance required BASE 6000 MORE THAN

60NM INLAND

Intensify/intensifying INTSF Change in intensity WINDS ALL LEVELS INTSF

BY 20KTS FM 06Z

Isolated ISOL Weather and cloud amount

description

Kilometre KM Distance

Knots KT Speed

Lee/Leeward Use to be minimised and

only used when it is difficult

to describe a direction.

MOD TURB BLW 5000FT LEE

RANGES

Level/s Vertical extent WINDS ALL LEVELS VRB/10

FM 09Z

Light - Weather intensity

Lighter Wind description WINDS 15KT LIGHTER

AFTER 14Z

Line LINE Geographical description

Low drifting DR Weather descriptor

Low/Tropical Low Synoptic feature

Maritime Geographical description SHRA MARITIME

Mist BR Weather phenomenon

Moderate MOD Intensity description


28

More than Geographical description BASE 6000 MORE THAN

60NM INLAND

Mountain waves MTW Weather phenomenon

Mountain/s MT Use to be minimised and



LOW CLOUD MOUNTAINS

TO COAST

Move or moving or

movement

MOV TROUGH MOV E TO BE

NEAR YEML/YBCG

Nautical miles NM Distance

Nil Significant To be used in weather,

cloud, icing and turb

sections. NOSIG not to be

used

Nimbostratus NS Cloud type

Nimbostratus NS Cloud type

North N Direction N OF 20S

Northeast NE Direction NE OF TROUGH

Northwest NW Direction NW OF YLGB/YPKU

Occasional or

occasionally

OCNL Weather and cloud amount

description

Offshore Distance required SHRA MORE THAN 30NM

OFFSHORE

Otherwise OTHERWISE NIL

SIGNIFICANT WEATHER

Overcast OVC Cloud amount

Rain RA Weather phenomenon

Ranges Use to be minimised and



ISOLATED SHOWERS

SEA/COAST/EASTERN

SLOPES GREAT DIVIDING

RANGE

Remainder Geographical description,

may be used in

subdivisions

SUBDIVISIONS: A: E OF 25S;

B: REMAINDER

Ridge Synoptic feature


29

Sandstorm SS Weather phenomenon

Scattered SCT Weather and cloud amount

description

Sea SEA Geographical description

Sea state Used in remark section if

required

Severe SEV Intensity description

Shallow fog MIFG Weather phenomenon

Shower SH Weather phenomenon

Slopes Orientation to be included. ISOLATED LOW CLOUD

COAST TO EASTERN

SLOPES OF GREAT

DIVIDING RANGES.

Small hail GS Weather phenomenon

Smoke FU Weather phenomenon

Snow SN Weather phenomenon

Snow SN Weather phenomenon

Snow shower SHSN Weather phenomenon

South S Direction S OF TROUGH

Southeast SE Direction SE OF ISLAV/YWIR

Southwest SW Direction SW OF FRONT

Squall/squall line SQ/SQL Weather phenomenon

Stationary STNR used to describe synoptic

features

Stratocumulus SC Cloud type

Stratus ST Cloud type

Stronger Wind description WINDS 10KT STRONGER S

OF S OF CANDY/YPOD

Temperature T Used within remarks

sections of winds


30

Tending Used to describe spatial

changes,

BASE TENDING 5000 MORE

THAN 60NM INLAND

Throughout Geographical description

Thunderstorm TS Weather phenomenon

Till TILL Temporal description

Towering cumulus TCU cloud type

Trough Synoptic feature

Turbulence TURB Weather phenomenon

Unrestricted Used for visibility

UTC time Z Time

Valley/s Geographical description

Variable VRB Wind description

Warmer Used for describing

temperatures

Weaken or

weakening

WKN Change in intensity

Weather Section heading NIL SIGNIFICANT WEATHER

West W Direction W OF

Widespread WDSPR Weather and cloud amount

description

Wind/s Used to describe winds

Windward Use to be minimised and

only used when it is difficult

to describe a direction.

SHOWERS SEA AND

WINDWARD OF GREAT

DIVIDING RANGE

Within WI Geographical description BKN ST 0500/2000 WI 30NM

COAST

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