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U.S. DEPARTMENT OF COMMERCEMay 27, 1988 W/OM13x2
TO: All Holders of Operations Manual
SUBJECT: Transmittal Memorandum for Operations Manual Issuance 88-5
1. Material Transmitted:
WSOM Chapter D-38, International Aviation In-Flight Advisories.
2. Summary:
The entire chapter has been revised. Major changes are as follows:
a. Two new meteorological watch offices (MWO) -- Fairbanks and Juneau, in Alaska -- have been established to enable the National Weather Service to provide MWO services for the expanded volume of airspace for which the United States now has air traffic service (ATS) responsibility in the International Civil Aviation Organization (ICAO). The increased ATS respon6ibility is reflected in the designation by the U.S. of two new ICAO flight information region6 (FIR) (Anchorage Continental and Anchorage Arctic) covering the land mass of Alaska, Alaskan coastal waters, and the area of the Arctic Ocean north of Alaska. (Section 2.1 and Appendix A.)
b. The responsibility for meteorological consultation has been added to the functions of some MWO's. (Sections 1.4 and 2.2)
c. The requirement for the issuance of SIGMET's related to volcanic ash clouds has been added. (Section6 1.5, 4, and 5.)
d. Terms used to specify the degree of obligation with reference to stated practices or procedures have been defined. (Section 3.)
e. A note explaining the meaning of the terms "subsonic cruising levels," "transonic levels," and "supersonic cruising levels" has been added. (Section 5.)
f. Issuance instructions concerning SIGMET amendment and cancellation messages, including examples, have been added. (Sections 7.2 and 7.3)
g. A recommendation for coordination and transfer of responsibility concerning SIGMET's related to hazardous weather impacting or that may impact two or more FIR's and/or MWO areas of responsibility has been added. (Section 9.)
h. An explanation of the exchange formula used as the basis for the development of the distribution table (Appendix D) has been added. (Section 10.)
i. A unique arrangement has been decided upon whereby SIGMET's issued by the three Alaska MWO's (Anchorage, Fairbanks, and Juneau) are distributed in Alaska under domestic headers and elsewhere under international headers. (Appendix B.)
3. Effecton Other Instructions:
This issuance supersedes all previously issued instructions concerning the preparation, issuance, and distribution of international in-flight advisories including WSOM Chapter D-38, issuance 73-4, dated February 22, 1973; issuance 75-16, dated July 24, 1975; and OML 13-79, dated August 21, 1979 (filed with D-38).
Elbert W. Friday, Jr.
Assistant Administrator
for Weather Services
Issue Date Org. Code NATIONAL WEATHER SERVICE Part Chap.
5-27-88 W/OM13x2 Operations Manual D 38
International Aviation In-Flight Advisories
Table of Contents:
1. General
1.1 Major U.S. Meteorological Watch Office (MWO) Functions
1.2 Relationship of MWO and Flight Information Region
1.3 Responsibility for SIGNET Dissemination
1.4 Responsibility for Meteorological Consultation
1.5 SIGMET Valid Periods
1.6 Use of Abbreviated Plain Language
2.1 Meteorological Watch Office Designations
2.2 Meteorological Consultation Office Designations
3. Use of Terms
4. Definition of SIGMET Information
5. Elements of SIGMET Information
5.1 "Active Thunderstorms" Defined
5.2 Use of Terms "SIGMET" and "SIGMET SST"
5.3 Unnecessary Descriptive Material
6. Areas of MWO Responsibility
7.1 SIGMET Messages
7.2 SIGMET Amendment Messages
7.3 SIGMET Cancellation Messages
8. SIGMET Issuance and Identification
8.1 Heading Assignments
8.2 SIGMET Preambles
9. Coordination and Transfer of Responsibility
9.1 Tracking Continuity Involving Two or More MWO's
9.2 Hazardous Weather Event Affecting Two or More FIR's and/or MWO's
9.2.1 One FIR, One ARTCC, Two WWO
9.2.2 Two FIR's, One ARTCC, One MWO
9.2.3 Two FIR's, Two ARTCC's, One MWO
9.2.4 Two FIR's, Two ARTCC's, Two MWO's
9.2.5 Three FIR's, Three ARTCC's, Three MWO's
10. SIGMET Distribution Requirements
10.1 SIGMET Exchange Formula
10.2 SIGMET Perishability
11. Display of SIGMET's by Airport MET Offices
Appendices:
A - Flight Information Regions and MWO Areas of Responsibility
B - Abbreviated Headings Assignments
D - SIGMET Distribution Requirements
E - Examples of International SIGMET's
1. General. Meteorological watch offices (MWO) are designated by the International Civil Aviation Organization (ICAO) and assigned specific areas of responsibility. These actions are taken in concert with the ICAO contracting state (i.e., ICAO member country) concerned.
l.1 Major U.S. Meteorological Watch Office (MWO) Functions. A U.S. MWO should, to the extent practicable, maintain continuous watch over meteorological (MET) conditions affecting flight operations within its area of responsibility. However, in areas or for flight levels (FL) where there is a low density of traffic, the watch may be restricted to times or flight levels relevant to expected flight operations. A U.S. MWO is responsible for:
a. preparing SIGMET information (see section 4 for definition) relating to its area of responsibility,
b. supplying SIGMET information to associated air traffic services (ATS) units,
c. amending SIGMET messages as required,
d. canceling SIGMET messages when the phenomena are no longer occurring or are no longer expected to occur in the area, and
e. supplying, to associated ATS units, information received on pre-eruption volcanic activity, on a volcanic eruption, and/or on volcanic ash cloud for which no SIGMET has already been issued.
1.2 Relationship of MWO and Flight Information Region. The boundaries of an MW0 area of responsibility should be coincident with the boundaries of a flight information region (FIR). This policy is followed, as far as practicable, by the.U.S. See section 6 and appendix A for further details.
1.3 Responsibility for SIGMET Dissemination. MWO's are responsible for disseminating SIGMET information in accordance with agreed ICAO requirements.In the U.S., this responsibility is discharged, in the case of airport meteorological office and MWO requirements, by the National Weather Service's (NWS) Office of Systems Operations (OSO), and in the case of ATS unit requirements, by the Federal Aviation Administration (FAA). Responsibility for the international exchange of SIGMET's prepared by U.S. MWO's and for the transmission, as available, of required SIGMET's to the FAA rests with the NWS's OSO. It is expected that international flight operators desiring to receive international SIGMET's will make needed arrangements with the FAA or the NWS for the inclusion of such SIGMET's on the appropriate airline circuit or other circuits or service (e.g., the FAA's Service "A" or the NWS's Family of Services).
1.4 Responsibility for Meteorological Consultation. An ICAO recommended practice states, meteorological offices should be so situated as to facilitate personal consultation between meteorological personnel and personnel of units providing air traffic services. Where colocation is not practicable, the required consultation should be achieved by other means." (Reference is paragraph 7.1.1.2, ICAO Annex 11, Air Traffic Services.) accordingly, U.S. MWO's are designated (see section 2.2 to fulfill this responsibility. The meteorologist in charge of each designated office should, on occasion as needed:
a. Consult with the manager of the air route traffic control center (ARTCC) being served as to the adequacy of the international SIGMET plan, as given by this chapter, relevant to the needs of the ARTCC for SIGMET information, and recommend measures as considered advisable to NWS Headquarters (attention: Aviation Services Branch) for adjustment of the plan.
b. Review, or arrange for the review of, the receipt of SIGMET information by the ARTCC to determine whether transit time requirements as established by ICAO (5 minutes from SIGNET message file time to receipt by the ARTCC) are being met and, if not, forward information to NWS Headquarters (attention: Aviation Services Branch) on deficiencies that are revealed. (Note: It should be noted that the SIGMET's required by each ARTCC are also required by its meteorological consulting office. See appendix D.)
c. Emphasize to the manager of the ARTCC that a very important source of information on which SIGMET's may be based is special air reports and that such reports as may be received by the ARTCC should be passed without delay to the MWO whose area of responsibility was affected by the information in the report(s).
d. (Applicable to MWO's Anchorage and San Francisco only.) Consult as considered advisable and as practicable with the meteorologist in charge (official in charge in the case of MWO Guam) of the other MWO's serving the Anchorage and the Oakland centers, respectively, as to the procedures in use by each MWO in meeting the SIGMET requirements of the center. The purpose of such consultation is to ensure, insofar as practicable, that the quality of the MWO service tot he relevant center is of an acceptable level and uniformity for all relevant areas.
1.5 SIGMET Valid Periods. ICAO standards and recommended practices state that SIGMET's should be for periods no greater than 6 hours and preferably for periods no greater than 4 hours except in the special case of volcanic ash cloud where the period may be extended up to 12 hours. U.S. SIGMET messages, except those related to tropical cyclones or to volcanic ash cloud, shall be valid for periods not longer than 4 hours. U.S. SIGMET messages related to tropical cyclones may be valid for periods not longer than 6 hours. The rationale behind the longer validity periods allowed for SIGMET's related to tropical cyclones is based on two features: (1) the relatively slow and predictable forward movement of tropical cyclones, permitting somewhat better detection and prediction of associated phenomena, and (2) the relatively long life of tropical cyclones, leading to a need to limit the number of SIGMET's. U.S. SIGMET messages related to volcanic ash cloud may be valid for periods not longer than 12 hours. The rationale for the still longer validity periods for volcanic ash cloud SIGMET's is based on the cycling of satellite observations, on the relatively long life volcanic ash clouds may have, on the relative accuracy of trajectory and dispersion forecasting, and on the needs of the aviation community for longer warning periods related to this phenomenon.
1.6 Use of Abbreviated Plain Language. SIGMET messages originated by U.S. MWO's shall be prepared in abbreviated plain language, using approved ICAO abbreviations considered by the issuing meteorologist to be readily understood and numerical values of self-explanatory nature supplemented, if suitable approved abbreviations are not available, by concise text in English. ICAO abbreviations considered by the meteorologist not to be readily understood should not be used; in this case the intended meaning should be spelled out. ICAO abbreviations are given by ICAO Document 8400, "ICAO Abbreviations and Codes." A copy of this document should be available at each MWO; the document may be obtained from the Aviation Services Branch.
MWO; the document may be obtained from the Aviation Services Branch.
2. Designation of Meteorological Watch Offices and of Offices Responsible for Meteorological Consultation. These designations are given below.
2.1 Meteorological Watch Office Designations. U.S. forecast offices designated by the U.S. as an MWO, and so indicated in relevant ICAO documents, are the following:
Naval Oceanography Command Detachment, Guam, Mariana Islands
Weather Service Forecast Office, Anchorage, Alaska
Weather Service Forecast Office, Fairbanks, Alaska
Weather Service Forecast Office, Honolulu, Hawaii
Weather Service Forecast Office, Juneau, Alaska
Weather Service Forecast Office, Miami, Florida
Weather Service Forecast Office, San Francisco, California
Weather Service Forecast Office, San Juan, Puerto Rico
Weather Service Forecast Office, Washington, D.C.
2.2 Meteorological Consultation Office Designations. Meteorologists in charge of the following offices are responsible for consulting with and advising the managers of the indicated ATS units.
Consultation Office ATS Unit and Related FIR(s)
MWO Anchorage Anchorage ARTCC -- Anchorage Oceanic, Anchorage Continental, and Anchorage Arctic FIR's
MWO Miami Houston ARTCC -- Houston Oceanic FIR and Miami ARTCC -- Miami Oceanic FIR
MWO San Francisco Oakland ARTCC -- Oakland Oceanic FIR
MWO Washington New York ARTCC -- New York Oceanic FIR
3. Use of Terms. The terms defined below are used in this chapter to specify policy concerning the de8ree of obligation with reference to stated procedures or practices:
"Shall" -- means that a practice or procedure is mandatory.
"Should" -- means that a practice or procedure is recommended.
"May" or "need not" -- means that a practice or procedure is optional.
"Will" -- means futurity, not a requirement to be applied to a procedure or practice.
4. Definition of SIGMET Information. SIGMET information is information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified enroute weather phenomena (or volcanic ash cloud) which may affect the safety of aircraft operations. SIGMET information also concerns the development of such phenomena in time and space.
5. Element of SIGMET Information. SIGMET information shall include the occurrence and/or expected occurrence of one or more of the following:
a. at subsonic cruising levels:
- active thunderstorms
- tropical cyclone
- severe line
-squall
- heavy hail
- severe turbulence
- severe icing
-marked mountain waves
- widespread sandstorm/duststorm
-volcanic ash cloud
b. at transonic levels and supersonic cruising levels:
- moderate or severe turbulence
- cumulonimbus clouds
- hail
- volcanic ash cloud.
Note: The term "subsonic cruising levels," "transonic levels," and "supersonic cruising levels" and the associated criteria are taken from ICAO Annex 3, Chapter 7, and are acknowledged to be ambiguous, often representing considerable overlap. For example, subsonic aircraft may operate at FL530 or higher and aircraft capable of flying faster than the speed of sound may begin transonic operations (i.e., transitioning from subsonic to supersonic speeds) at FL250 or even lower. The significance of the distinction between meteorological effects as given by paragraphs 5a and 5b, above, is that aircraft operating at supersonic speeds conditions generally considered not to be hazardous to aircraft operating at speeds below the speed of sound. Supersonic cruising levels are generally considered to be at or above FLS30 and subsonic cruising levels are generally considered to be at or below FLS30.
5.1 "Active Thunderstorms" Defined . The requirement to issue SIGMET information regarding active thunderstorms refers to the occurrence or expected occurrence of an area (3000 square nautical miles or more) of widespread cumulonimbus clouds or cumulonimbus embedded in cloud layers or concealed by haze. It does not refer to isolated or scattered cumulonimbus not embedded in cloud layers or concealed by haze. From a different perspective, cumulonimbus clouds that can be avoided by visual observation from the flight deck are not considered to be "active thunderstorms" in the sense of this definition.
5.2 Use of Terms "SIGMET" and "SIGMET SST." SIGMET messages prepared for phenomena related to subsonic cruising levels shall be designated "SIGMET" in the message preamble. Those prepared for phenomena related to transonic levels or supersonic cruising levels shall be designated "SIGMET SST" in the message preamble.
5.3 Unnecessary Descriptive Material . SIGMET messages should not contain unnecessary descriptive material. For example, messages concerning an area of active thunderstorm , a tropical cyclone, or a severe line squall should not include references to associated turbulence, icing, or hail, unless the associated phenomena are considered to warrant special attention. In tropical areas, during periods when thunderstorm activity is a frequent occurrence,SIGMET messages relating to that phenomenon should only be issued with respect to active thunderstorms as defined in section 5.1, above.
6. Areas of MWO Responsibility. These areas are shown by appendix A.
7. Formats of SIGMET Messages. SIGMET messages, including SIGMET amendments and cancellations, shall contain certain information as given below.
7.1 SIGMET Messages. A SIGMET message issued by a U.S. MWO shall contain the following information as necessary and in the order indicated.
a. Location indicator of the ATS Unit(s) serving the FIR(s) to which the SIGMET message refers, for example, KZOA (the location indicator of the Oakland ARTCC).
b. Message identification and sequence number, for example, SIGMET OSCAR 1.
c. Date-time groups indicating the period of validity, for example, valid from 1215 coordinated universal time (UTC) to 1600 UTC on the 22nd day of the month (which should be written as 221215/221600).
d. Location indicator of the MWO originating the message, followed without a space by a hyphen to separate the preamble from the text, for example, KSFO-.
Note: Section 7.1 (a-d) gives the information required to be included in a SIGMET's preamble. It is suggested that, because of the preamble's length, only the preamble occupy the first line and that the text begin on the second line.
e. Phenomenon causing the issuance of the message, for example, airport of severe turbulence.
f. Descriptive remark(s) referring to the phenomenon, for example, in clear air.
8. Indication of whether the phenomenon is observed or forecast and related time (if 9ppropriate), for example, observed at 1205 UTC.
h. Location and FL, for example, 45N131W at FL350
i. Movement or expected movement given in knots, for example, moving east at 25 knots, i.e., MOV E 25 KT.
j. Changes in intensity, using, as appropriate, the terms "intensifying," "weakening," or "no change," i.e., INTSF, WKN, or NC, as appropriate.
7.2 SIGMET Amendment Messages. The format of an amendment message should be similar to that of normal SIGMET messages, i.e., the amendment message shou1d contain data for items a through ; similar to those given under 7.1 above. Following item d, however, would be the words "AMENDS SIGMET" followed by the identification and sequence number of the message being amended, for example, "AMENDS SIGMET OSCAR 1." Items e through j would be prepared to reflect the new circumstances. Examples of an original SIGMET message followed by a SIGMET amendment message are given below.
a. Original SIGMET Message::
WSPAl PHNL 100325
KZOA SIGMET ROMEO 1 VALID 100330/100730 PHNL-
SEV LSQ OBS AT 0315 UTC 30N170W TO 20N178W. CB TOPS FL350.
MOV E 30 KT. WKN.
b. SIGMET Amendment Message:
WSPSl PHNL 100440
KZOA SIGMET ROMEO 2 VALID 100445/100845 PHNL-
AMENDS SIGMET ROMEO 1. SEV LSQ OBS AT 0430 UTC 32N170W TO
18N178W. CB TOPS FL480. MOV E 20 KT. INTSF.
7.3 SIGMET Cancellation Messages. The format of a cancellation message should consist of the identification of the message being canceled followed by the words "IS CNL WEF (TIME) UTC" and an explanation of the cancellation. Examples of an original SIGMET message followed by a message canceling it are given below:
a. Original SIGMET message:
WSPAl PHNL 100335
KZOA SIGMET SIERRA 1 VALID 100330/100730 PHNL-
SEV LSQ OBS AT 0315 UTC 30N170W TO 2N178W. CB TOPS FL350
MOV E 30 KT. WKN.
b. SIGMET Cancellation message:
WSPA 1 PHNL 100440
KZOA SIGMET SIERRA 1 IS CNL WEF 0440 UTC. ACFT REP INDICATES
LSQ HAS DISSIPATED.
8. SIGMET Issuance and Identification. SIGMET messages shall be issued as meteorological bulletins and shall be identified as to the ARTCC with ATS responsibility for the FIR to which they refer. The purpose of such identification is to enable the SIGMET to be stored in a H8T data bank and to be retrievable by procedures related to the FIR. The identification is to be included in an appropriate preamble to the text of the SIGMET message as explained in Section 8.2, below.
8.1 Heading Assignments. SIGMET messages issued by U.S. MWO's are assigned headings as shown in appendix B.
8.2 SIGMET Preambles. The identification feature of a SIGMET messages relating it to a specific FIR is a preamble giving the information called for by section 7.1 (a-d) above. Further details, including examples of such preambles, are given in appendix C.
9. Coordination and Transfer of Responsibility. Weather events for which SIGMET messages may need to be issued may occur along or near the boundaries of FIR's and/or MWO areas of responsibility. Such events create problems in the continuity of tracking and in ensuring SIGMET message receipt by users as required. Careful attention and coordination should be given by MWO's to this situation.
9.1 Tracking Continuity Involving Two or More MWO's. Information concerning the issuance of SIGNET messages related to areas along or near the border of responsibility between two or more MWO's (including adjacent Canadian MWO's) should be exchanged between/among the relevant MWO's by telegraphic or telephone messages. This helps to ensure continuity in tracking the hazardous weather. The MWO in whose area of responsibility the hazardous weather has been observed or forecast should take the initiative to pass the relevant information to the MWO(s) into whose area(s) the hazardous weather is moving. The identification procedures applicable to SIGMET information related to hazardous weather moving from an MWO's area of responsibility to other areas should be as described in appendix C.
9.2 Hazardous Weather Event Affecting Two or More FIR's and/or MWO's. single weather event often affects more than one FIR and may fall within area(s) of responsibility of more than one MWO. Guidelines which should help ensure that SIGMET messages related to such events reach appropriate ATS units, aircraft operators, and MET offices follow.
9.2.1 One FIR, One ARTCC. Two MWO's. Issue one SIGNET, if coordinated between the MWO's, by one or the other MWO. If coordination is not practicable, each MWO should issue a SIGNET. Preamble example:
PAZA SIGMET KILO 1 VALID 061100/061400 PAFA-
(SIGMET in area of ATS responsibility of Anchorage and Fairbanks. Issued by MWO Fairbanks. Affects the area on both sides of the boundary between the MWO's.)
9.2.2 Two FIR's, One ARTCC, one MWO. Issue one SIGMET. Preamble example:
PAZA SIGMET ALFA 1 VALID 021200/021600 PANC-
(SIGMET straddling the boundary between the Anchorage Oceanic and the Anchorage Continental FIR's, about 51N175E, in area of ATS responsibility of the Anchorage ARTCC and of the MWO responsibility of MWO Anchorage )
9.2.3 Two FlR's, Two ARTCC's, One MWO. Issue one SIGMET. Preamble:
example:
KZOA PAZA SIGMET CHARLIE 1 VALID 041700/042100 PANC-
(SIGMET straddling the boundary between the Anchorage Oceanic and
the Oakland Oceanic FIR's, about 53N162W, in areas of ATS
responsibility of both the Anchorage and Oakland ARTCC's and of MWO
responsibility of the Anchorage MWO. Note that the preamble
contains the identifiers of both ARTCC's.)
9.2.4 Two FIR's, Two ARTCC's. Two MWO's. Issue one coordinated SIGMET by one or the other of the relevant MWO's. If coordination is not practicable, each MWO should issue a SIGMET. Preamble examples:
PAZA KZOA SIGMET GOLF 1 VALID 091400/091800 PAJN- (SIGMET straddling the border between the Anchorage Continental and the Oakland Oceanic FIR's, about 55N143W, in areas of ATS responsibility of both the Anchorage and the Oakland ARTCC's and of MWO responsibility of both MWO's Anchorage and Juneau. Coordinated issuance.)
PAZA KZOA SIGMET HOTEL 1 VALID 091400/091800 PAJN-(Same situation as preceding SIGMET except that coordination between MWO's Anchorage and Juneau was not effected. Issued by MWO Juneau.)
KZOA PAZA SIGMET BRAVO 1 VALID 091405/091805 PANC- (Same situation as before. Coordination between the MWO's not effected. Issued by MWO Anchorage.)
9.2.5 Three FIR's, Three ARTCC's. Three MWO's. Issue one coordinated SIGMET if practicable; if not, each involved MWO should issue a SIGMET. Preamble example:
KZMA TJZS KZNY SIGMET YANKEE 1 VALID 070700/071100 TJSJ- (SIGMET coordinated among MWO's Miami, San Juan, and Washington. Relates to area near juncture of the Miami Oceanic, the New York Oceanic, and the San Juan FIR's, i.e., about 27N6930W. This area falls within the areas of ATS responsibility of the Miami, the San Juan, and the New York ARTCC's and of MWO responsibility of MWO's Miami, San Juan, and Washington. If coordination should be impracticable, each MWO should issue a SIGMET, and each should contain a preamble with the identifiers for all three ARTCC's. (issued by MWO San Juan.)
10. SIGMET Distribution Requirements. International SIGMET's are required to be distributed in accordance with international agreements developed under the auspices of ICAO. The agreed requirements, however, may reflect only the total requirements of an ICAO contracting state and not those of individual ATS units or MET offices of the contracting state. Accordingly, it is necessary to determine those specific ATS unit or MET office requirements based on an ICAO formula for SIGMET exchange.
10.1 SIGMET Exchange Formula. This formula, which is given in the ICAO air navigation plan (ANP) publications, requires that SIGMET's be available:
a. at the aircraft's departure airport, for the route ahead up to a distance corresponding to 2 hours' flying time (generally regarded as 1100 nautical miles); and
10.2 SIGMET Perishability. SIGMET's are considered to be among the most highly perishable of all aeronautical operational meteorological data. To meet ground exchange requirements, SIGMET's must be given immediate and reliable distribution to the maximum extent practicable to ensure availability at:
a. ATS units serving international aviation within 2 hours' flying time of the area for which an MWO is responsible, provided aircraft operations from the area of responsibility of such ATS units may be expected to penetrate the MWO's area of responsibility; and
b. airport MET offices serving international aviation within 2 hours' flying time of the area for which an MWO is responsible, provided aircraft operations from airports served by such, meteorological offices may be expected to penetrate the MWO's area of responsibility.
11. Display of SIGMET's by Airport MET offices. Airport MET offices that serve international flight operations should display required international SIGMET's prominently.
12. Records Retention. Records of issued SIGMET's, including amendments and notices of cancellation, shall be maintained as called for by WSOM Chapter D-90, Weather Support for Accident Investigations and Litigation.
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World Meteorological Organizations (WMO) abbreviated headings, U.S. domestic headings, and AFOS Product Inventory List (PIL) headers which should be used, as appropriate, for the issuance of SIGMET messages are as follows:
| Meteorological Watch Office |
WMO Abbreviated Heading |
U.S. Domestic Heading |
AFOS PIL Header |
| Anchoragel | WSPNl PANC | ANCA to E WS | NMWS8A to E |
| Fairbanksl | WSACl PAFA | FAIJ to N WS | NMCWS9J to N |
| Guam | WSPA PGUM | (none) | PASIG11 |
| Juneaul | WSPNl PAJN | JNUF to I WS | NMCWS7F to I |
| Honolulu | WSPAl PHNL2 | (none) | HNLSIGHNL2 |
| WSPA2 PHUL3 | (none) | HNLSIG63 | |
| Miami | WSCA KMIA | (none) | MIASIGO to R |
| San Francisco | WSPAl KSFO (none) | SFOSIGW to Z | |
| San Juan | WSCA TJSJ | (none) | SJUSIGW to Z |
|
Washington
|
WSNT KWBC
|
(none)
|
WBCSIGS to V
|
Notes:
1. SIGMET's prepared by MWO'S Anchorage, Fairbanks, and Juneau are issued under domestic headings (see WSOM Chapter D-22) and transposed to the appropriate WMO abbreviated heading by the FAA's National Communications Center (NATCOM) at Kansas City. NATCOM then transmits the SIGNET, under the WMO header, to KWBC for distribution.
2. For SIGMET's (including volcanic ash cloud SIGMET's) not related to tropical cyclones.
3. For SIGMET's related to tropical cyclones. Warning periods of up to 6 hours are allowed for U.S. international SIGMET's related to tropical cyclones.
Each preamble should include a sequence consisting of a phonetic word representing a Letter of the alphabet followed by a number. Individual MWO's are assigned phonetic words for this purpose. Phonetic words may be repeated when necessary (for example, ALFA ALFA 1) to cope with a situation involving more simultaneous SIGMET events in an MWO's area than the number of phonetic words assigned to an MWO. The assignments, intended to minimize confusion, are as follows:
MWO Anchorage - Alfa, Bravo, Charlie, Delta, Echo
MWO Juneau - Foxtrot, Golf, Hotel, India
MWO Fairbanks - Juliett, Kilo, Lima, Mike, November
MWO Guam - Oscar, Papa, Quebec
MWO Honolulu - Romeo, Sierra, Tango, Uniform, Victor
MWO San Francisco - Whiskey, X-ray, Yankee, Zulu
MWO Miami - Oscar, Papa, Quebec, Romeo
MWO Washington - Sierra, Tango, Uniform, Victor
MWO San Juan - Whiskey, X-ray, Yankee, Zulu
The phonetic word should refer to a phenomenon (or phenomena) associated with a specific weather system. As an explanation, the first time a SIGMET is issued by an MWO for active thunderstorms associated with a specific intense low-pressure area, the SIGMET should be assigned the next unassigned phonetic word and should be numbered as the first SIGMET related to the phenomenon. An example might be SIGMET OSCAR 1. The compete preamble for such a SIGMET, issued, for example, by MWO Miami, could be:
KZHU SIGMET SOCAR 1 VALID 050745/051115 KMIA-
This would be a SIGMET concerning hazardous weather in the Houston Oceanic FIR; it would be the first one issued by MWO Miami concerning a phenomenon (or phenomena) related to a specific weather system. Its use, for that particular weather system, would be continued (beyond 2400 UTC if necessary) as long as the issuing MWO would issue SIGMET's for phenomena related to the system. the number following the alphabetic identifier (OSCAR in this case) would identify the SIGMET as the first one issued for hazardous phenomenon/phenomena associated with the weather system in question. the SIGMET would be valid for 3 hours 30 minutes following 0745 UTC. Subsequent SIGMET related to the same weather system would carry the sequence identification OSCAR 2, OSCAR 3, etc., continuing beyond 2400 UTC if necessary, reaching, for example, OSCAR 8 or some larger number. It should retain the alphabetic designator until the phenomenon ends or moves into another MWO's area of responsibility. In the case of an alphabetically identified series continued beyond 2400 UTC, the date-time group of the heading as well as the date-time groups giving the validity period should distinguish the SIGMET message from those of the previous day.
Example of appropriate SIGMET preambles (with underlining to identify the preambles) are given below:
1. Example of SIGMET preamble for SIGMET issued by MWO Anchorage related to the Oakland Oceanic Flight Information Region:
WSPN1 PANC 051757
KZOA SIGMET CHARLIE 1 VALID 051810/052200 PANC-
(Text follows)
2. Example of SIGMET preamble for SIGMET issued by MWO Fairbanks related to the Anchorage Arctic Flight Information Region:
WSAC1 PAFA 071825
PAZA SIGMET KILO 2 VALID 071835/072100 PAFA-
(Text follows)
3. Example of SIGMET preamble for SIGMET issued by MWO Anchorage related to the Anchorage Oceanic Flight Information Region:
WSPN1 PANC 051802
PAZA SIGMET DELTA 1 VALID 051815/052215 PANC-
(Text follows)
4. Example of SIGMET preamble for SIGMET issued by MWO Juneau related to the Anchorage Continental Flight Information Region:
WSPN1 PJNU 051805
PAZA SIGMET FOXTROT 1 VALID 051820/052220 PAJN-
(Text follows)
5. Example of SIGMET preamble for SIGMET issued by MWO Guam related to the Oakland Oceanic Flight Information Region:
WSPA PGUM 051821
KZOA SIGMET OSCAR OSCAR 1 VALID 051830/052230 PGUM-
(Text follows. Note that the identification is OSCAR OSCAR 1. what this means is that SIGMET's for three simultaneously existing hazardous weather events have been issue by MWO Guam, using up all the three individual alphabetic series available -- OSCAR, PAPA, and QUEBEC -- and Guam then assigns, as the next alphabetic identification, the OSCAR OSCAR series. The next available series, should double up still be required, would be PAPA PAPA. Such a circumstance is considered to be unlikely to occur .)
6. Example of SIGMET preamble for SIGMET issued by MWO Honolulu related to the Oakland Oceanic Flight Information Region:
WSPA1 PHNL 051750
KZOA SIGMET ROMEO 3 VALID 051800/052200 PHNL-
(Text follows)
7. Example of SIGMET preamble for SIGMET issued by MWO Honolulu, pertaining to phenomena related to a tropical cyclone, for the Oakland Oceanic Flight Information Region:
WSPA2 PHNL 051755
KZOA SIGMET SIERRA 1 VALID 051810/060010 PHNL-
(Text follows)
8. Example of SIGMET preamble for SIGMET issued by MWO San Francisco related to the Oakland Oceanic Flight Information Region:
WSPA1 KSFO 051737
KZOA SIGMET WHISKEY 1 VALID 051745/052100 KSFO-
(Text follows)
9. Example of SIGMET preamble for SIGMET issued by MWO Miami related to the Houston Oceanic Flight Information Region:
WSCA KMIA 090905
KZHU SIGMET QUEBEC 2 VALID 090910/091310 KMIA-
(Text follows)
10. Example of SIGMET preamble for SIGMET issued by MWO Miami related to the Miami Oceanic Flight Information Region:
WSCA KMIA 101142
KZMA SIGME ROME 1 VALID 101150/101500 KMIA-
(Text follows)
11. Example of SIGMET preamble for SIGMET issued by MWO Washington related to the New York Oceanic Flight Information Region:
WSNT KWBC 120505
KZNY SIGMET VICTOR 3 VALID 120515/120900 KWBC-
(Text follows)
12. Example of SIGMET preamble for SIGMET issued by MWO San Juan related to the San Juan Flight Information Region:
WSCA TJSJ 131425
TJZS SIGMET ZULU 1 VALID 131435/131835 TJSJ-
(Text follows)
This appendix depicts the distribution requirements, so far as can be determined, of international SIGMET's required for international or long over water flights operating from the U.S., its territories or its possessions. the list given in the tables that follow on the next two pages (fold-outs are intended to help ensure correct and timely distribution of SIGMET's prepared by U.S. meteorological watch offices as well as relevant SIGMET's prepared by meteorological watch offices of other ICAO contracting states and transmitted to the U.S. to fulfill stated requirements.
Examples of SIGMET's such as might be issued by a U.S. MWO are given below.
Active Thunderstorms
WSPA PGU
KZOA SIGMET PAPA 1 VALID 090345/090700 PGUM-
WDSPR TS WI 50 NM EITHER SIDE OF LINE 16N144E 05N142E. TS TOPS FL430. MOV
W 10 KT. NC.
Tropical Cyclones
WSPA2 PHNL 100255
KZOA SIGMET SIERRA 1 VALID 100300/100900 PHNL-
TROPICAL STORM OKA OBS 10.2N 155.4W AT 0000 UTC. TS TOPS FL500 WITHIN 150
NM OF CENTER. MOV W 10 KT. INTSF. SEE LAmanual ADVISORY.
Severe Line Squall
WSPAl KSFO 100025
KZOA SIGMET X-RAY 1 VALID 100030/100430 KSFO
SEV LSQ OBS AT 0015 UTC 35N131W 25N139W. TS TOPS FL400. MOV E 20 KT. WKN.
Heavy Hail
WSCA KMIA 230957
KZHU KZMA SIGMET OSCAR 1 VALID 101745/102145 KMIA-
ACFT REP GR AT 1739 UTC FL390 26N86W. WDSPR TS IN AREA BOUNDED BY 28N88W
28N84W 26N87W 26N85W. CB TOPS FL420. MOV NE 15 KT. NC.
Severe Turbulence
WSNT1 KWBC 080255
KZNY SIGMET UNIFORM 2 VALID 080300/080700 KWBC-
MOD OR GREATER CAT BTN FL300 AND FL390 WITHIN 100 NM EITHER SIDE OF A
LINE 43N56W 35N65W. MOV E 25 KT. NC. BASED ON ACFT OBS AND PSN OF INTENSE
JTST
Severe Icing
WSCA TJSJ 101555 TJZS SIGMET YANKEE 1 VALID 101600/102000 TJSJSEV MIXED ICE BTN FL100 AND FL180 WI 100 NH EITHER SIDE OF FRONT 17N66W 22N61W 26N59W. BASED ON ACFT OBS. MOVE E 25 KT. NC.
Marked Mountain Waves
WSAC1 PAFA 181720
PAZA SIGMET JULIETT 1 VALID 181725/182125 PAFA-
MOD OR GREATER TURB AND ASSOCIATED MTW EFFECT FCST BLW FL350 60 NH EITHER
SIDE OF A LINE FM PAOR TO PAFA TO PAMC. NC.
Volcanic Ash Cloud
SPNl PANC 061745
PAZA SIGMET CHARLIE 1 VALID 061750/070550 PANC-
VOLCANIC ASH CLD FM ST AUGUSTINE VOLCANO 60N153W
60N148W 57N148W 57N153W 60N153W. TOP EST FL410. BASED ON SATELLITE OBS AT 1720 UTC AND ACFT REP
AT 1715 UTC. PILOT REP VIS IN CLD VERY LOW. MOV E 30 KT.
WSOM Issuance
88-5 5-27-88