Chapter 26, Advisories 26-1
26 Advisories
26.1 Introduction
The third of five types of aviation weather information contained in this handbook are advisories. For this
handbook, advisories include the following:
1. Significant Meteorological Information (SIGMET):
• Inside the CONUS:
o Non-Convective.
o Convective.
• Outside the CONUS.
2. Airmen’s Meteorological Information (AIRMET):
• Inside the CONUS.
• Outside the CONUS.
3. Center Weather Advisory (CWA).
4. Volcanic Ash Advisory (VAA).
5. Tropical Cyclone Advisory (TCA).
6. Space Weather Advisory.
7. Wind Shear Alerts.
8. Airport Weather Warning (AWW).
Chapter 26, Advisories 26-2
26.2 Significant Meteorological Information (SIGMET)
A SIGMET is a concise description of the occurrence or expected occurrence of specified en route weather
phenomena that may affect the safety of aircraft operations. SIGMETs are issued in text format and intended
for dissemination to all pilots in flight t o enhance safety. SIGMETs are issued as soon as practical to give
notice to operators and aircrews of potentially hazardous en route conditions.
Although the areas where the SIGMETs apply may be shown graphically, a graphical depiction of the
SIGMET area is not the entire SIGMET. Additional information regarding the SIGMET may be contained
in the text version.
26.2.1 SIGMET Issuance
SIGMETs are issued from MWO s. The United States has three MWOs: the AWC, the AAWU, and the
WFO Honolulu.
The AWC is responsible for:
• Twenty domestic ARTCC FIR s covering the CONUS and adjacent coastal waters. CONUS
SIGMETs, except for Convective SIGMETs, are grouped into six areas (see Figure 26-1).
• The New York, Houston, Miami, and San Juan Oceanic FIRs (see Figure 26-2).
• The Oakland Oceanic FIR north of 30°N latitude and the portion east of 140° W longitude, which
is between the Equator and 30°N latitude (see Figure 26-3).
The AAWU is responsible for the Anchorage Continental FIR and the Anchorage Oceanic FIR (see Figure
26-3).
WFO Honolulu is responsible for the Oakland Oceanic FIR south of 30°N latitude and between 140°W and
130°E longitude (see Figure 26-3).
Chapter 26, Advisories 26-3
Figure 26-1. AWC SIGMET Areas of Responsibility—CONUS
Figure 26-2. AWC SIGMET Areas of Responsibility—Atlantic Basin
Chapter 26, Advisories 26-4
Note that KKCI refers to the AWC that is in Kansas City, MO.
Figure 26-3. SIGMET Areas of Responsibility—Pacific Basin
26.2.2 SIGMET Identification
U.S. SIGMETs (other than Convective SIGMETs) are assigned a series identifier:
• AWC for the CONUS:
o NOVEMBER, OSCAR, PAPA, QUEBEC, ROMEO, UNIFORM, VICTOR, WHISKEY,
XRAY, and YANKEE. Note that SIERRA and TANGO are excluded.
• AWC for the Oakland Oceanic FIR:
o ALFA, BRAVO, CHARLIE, DELTA, ECHO, FOXTROT, GOLF, and HOTEL.
• Honolulu MWO for the Oakland Oceanic FIR:
o NOVEMBER, OSCAR, PAPA, QUEBEC, ROMEO, SIERRA, TANGO, UNIFORM,
VICTOR, WHISKEY, XRAY, YANKEE, and ZULU.
• AAWU for the Anchorage FIR:
o INDIA, JULIET, KILO, LIMA, and MIKE.
Chapter 26, Advisories 26-5
A number is assigned sequentially with each issuance until the phenomenon ends. At 0000 UTC each day,
all continuing SIGMETs are renumbered to one, regardless of a conti nuation of the phenomena
(e.g., YANKEE 1, YANKEE 2, YANKEE 3).
26.2.3 SIGMET Standardization
SIGMETs follow these standards:
• All heights or altitudes are referenced to above MSL, unless otherwise noted, and annotated using
the height in hundreds of feet, consisting of three digits (e.g., 040). For heights at or above 18,000 ft,
the level is preceded by “FL” (e.g., FL180).
• References to latitude and longitude are in whole degrees and minutes following the model:
Nddmm or Sddmm, Wdddmm, or Edddmm with a space between latitude and longitude and a
hyphen between successive points (e.g., N3106 W07118—N3011 W7209).
• Messages are prepared in abbreviated plain language using contractions from FAA
Order JO 7340.2, Contractions, for domestic products , and from ICAO Doc 8400, ICAO
Abbreviations and Codes, for international products issued for Oceanic FIRs. A limited number of
non-abbreviated words, geographical names, and numerical values of a self-explanatory nature may
also be used.
26.2.4 Inside the CONUS
26.2.4.1 Non-Convective SIGMET
26.2.4.1.1 Non-Convective SIGMET Issuance Criteria—CONUS
A SIGMET may be issued in the CONUS when any of the following conditions affect, or, in the judgment
of the forecaster, are expected to affect an area judged to have a significant impact on the safety of aircraft
operations:
• Severe or greater turbulence (SEV TURB).
• Severe icing (SEV ICE).
• Widespread dust storm (WDSPR DS).
• Widespread sandstorm (WDSPR SS).
• Volcanic ash (VA).
26.2.4.1.2 Non-Convective SIGMET Issuance Time and Valid Period—CONUS
A SIGMET is an unscheduled product issued any time conditions reaching SIGMET criteria are occurring
or expected to occur within a four-hour period. A SIGMET can have a valid period up to, but not exceeding,
four hours. SIGMETs for continuing phenomena will be reissued at least every four hours as long as
SIGMET conditions continue to occur in the area of responsibility.
26.2.4.1.3 Non-Convective SIGMET Format and Example—CONUS
The content and order of elements in the SIGMET are as follows:
• Series name and number.
• Valid beginning and ending time (UTC).
• List of states affected by the phenomena.
Chapter 26, Advisories 26-6
• Location of phenomena delineated by high -altitude VOR coordinates covering the affected area
during the SIGMET valid time.
• Phenomena description (e.g., SEV ICE).
• Vertical extent (base and top), if appropriate.
• Movement, if appropriate.
• Intensity change (INTSF—intensifying, WKN—weakening, NC—no change).
• Indication that the weather condition will continue during the four hours beyond the valid time of
the SIGMET.
SFOR UWS 100130
SIGMET ROMEO 1 VALID UNTIL 100530
OR WA
FROM SEA TO PDT TO EUG TO SEA
SEV TURB BTN FL280 AND FL350. CONDS CONTG BYD 0530Z.
Figure 26-4. Non-Convective SIGMET for the CONUS—Example
Table 26-1. Decoding a Non-Convective SIGMET for the CONUS
Line Content Description
1 SFO SIGMET area identifier
R SIGMET series
UWS Product identifier
100130 Issuance date/time UTC
2 SIGMET Product type
ROMEO SIGMET series name
1 Series issuance number
VALID UNTIL 100530 Ending valid date/time UTC
3 OR WA Phenomenon location (states)
4 FROM SEA TO PDT TO EUG TO SEA Phenomenon location
(high-altitude VOR coordinates)
5 SEV TURB BTN FL280 AND FL350.
CONDS CONTG BYD 1000Z Phenomenon description
Chapter 26, Advisories 26-7
The SIGMET in Figure 26-4 is decoded as the following:
• (Line 1) SIGMET ROMEO series issued for the San Francisco area at 0130 UTC on the 10th day
of the month.
• (Line 2) This is the first issuance of the SIGMET ROMEO series and is valid until the 10th day of
the month at 0530 UTC.
• (Line 3) The affected states within the San Francisco area are Oregon and Washington.
• (Line 4) From Seattle, WA; to Pendleton, OR; to Eugene, OR; to Seattle, WA.
• (Line 5) Severe turbulence between FL280 and FL350. Conditions continuing beyond 0530Z.
26.2.4.1.4 Non-Convective SIGMET Cancellations—CONUS
A CONUS Non-Convective SIGMET is cancelled when the phenomenon is no longer occurring, no longer
expected to occur, or has moved out of the area of responsibility.
26.2.4.1.5 Non-Convective SIGMET Amendments—CONUS
Amendments to CONUS Non-Convective SIGMETs are not issued. Instead, a new SIGMET is issued using
the next series number.
26.2.4.1.6 SIGMET (Non-Convective) Corrections—CONUS
Corrections to CONUS Non -Convective SIGMETs are issued as necessary. The corrected SIGMET is
identified by a “COR” located at the end of the first line after the issuance UTC date/time.
26.2.4.2 Convective SIGMET
Convective SIGMETs are issued for the CONUS instead of SIGMETs for thunderstorms. Any Convective
SIGMET implies severe or greater turbulence, severe icing, and LLWS.
Although the areas where the Convective SIGMETs apply may be shown graphically, such a graphical
depiction, the Convective SIGMET polygon is a “snapshot” that outlines the area (or line) of thunderstorms
at the issuance time of 55 minutes past each hour. During the valid time of the SIGMET, the area/line will
move according to the movement vector given in the SIGMET. For fast -moving areas or lines, they will
very likely end up outside the SIGMET polygon by the end of the hour. Slow -moving or stationary area s
or lines will likely remain in or very close to the original polygon. For additional clarification, the movement
“MOV FROM...” within the Convective SIGMET describes the current movement of the SIGMET area or
line. In cases when cell movements are different within the area, the SIGMET will include an additional
line that states “CELL MOV FROM.” Detailed information regarding the Convective SIGMET depiction
should be compared to the textual version for storm movement, velocity, cloud tops, and several othe r
important elements. Users should exercise caution as areas of convection and their associated polygons can
change and should only be used for strategic planning.