Chapter 3, Overview of Aviation Weather Information 3-24
Turbulence
Information
Contained In:
Type Summary
Low-Level SIGWX G Moderate or greater turbulence is depicted.
Medium-Level
SIGWX G Areas of non-convective clouds with moderate or severe turbulence are depicted.
High-Level SIGWX G Global forecasts of moderate or severe turbulence associated with wind shear
zones and mountain waves are depicted.
Alaska SIGWX G Areas of forecast moderate or greater non-convective low-level turbulence are
depicted.
WAFS G Global forecasts of turbulence provided in a grid point format primarily intended
for use in flight-planning systems.
MIS T A discussion of meteorological events (including turbulence information)
causing or expecting to impact the flow of air traffic across an ARTCC.
Tools
GFA Tool G Interactive website that includes turbulence (PIREP/AIREP, GTG, AIRMET,
SIGMET, and CWA).
Flight Service
Interactive Map G Interactive website that includes turbulence (PIREP/AIREP, GTG, AIRMET,
SIGMET, and CWA).
3.4.2.10 Products with Volcanic Ash Information
Table 3-13. Weather Element: Volcanic Ash
Type: text (T), graphic (G), image (I), voice (V)
Volcanic Ash
Information
Contained In:
Type Summary
Observations
METAR, SPECI
(ATIS)
T, G,
Reported in manual and select augmented METAR/SPECIs as “VA.” Included
in ATIS as appropriate.
PIREP/AIREP/VAR T, G,
Reported by pilot and noted as an Urgent PIREP or Special AIREP. First part of
VAR reported immediately to ATC, second part of VAR submitted postflight.
Radar I Potentially visible on radar.
Satellite I May be visible on satellite if not obscured by cloud cover.
Weather Camera I Volcanic ash cloud may be seen on the camera.
Analysis
See SIGMET and VAA
Advisories
SIGMET T, G One of the conditions that triggers the issuance of a SIGMET. Provides an
analysis and six-hour forecast location of the ash cloud.
VAA T, G
Provides an analysis, 6-, 12-, 18-, and 24-hour forecast location of the ash cloud.
Issued every six hours until the volcanic ash is no longer discernible from
satellite and no further reports of volcanic ash are received from the area.
CWA T, G One of the conditions that triggers the issuance of a CWA.
Chapter 3, Overview of Aviation Weather Information 3-25
Volcanic Ash
Information
Contained In:
Type Summary
Forecasts
TAF T Included when conditions are expected and indicated in the forecast as “VA”
under the significant weather group.
Alaska Area
Forecast T
Obstructions to visibility such as volcanic ash are noted in the description of
significant clouds and weather for the region during the first 12 hours of the
forecast period.
Hawaii Area
Forecast T
Obstructions to visibility such as volcanic ash are noted in the description of
significant clouds and weather for the region during the first 12 hours of the
forecast period.
Gulf of America and
Caribbean Area
Forecast
Obstructions to visibility such as volcanic ash are noted in the description of
significant clouds and weather for the region during the first 12 hours of the
forecast period.
Medium-Level
SIGWX G Erupting volcano is identified with a trapezoidal symbol along with the name,
latitude, and longitude. Location of ash cloud is not depicted.
High-Level SIGWX G Erupting volcano is identified with a trapezoidal symbol along with the name,
latitude, and longitude. Location of ash cloud is not depicted.
AFD T May include a discussion on volcanic ash when applicable.
MIS T A discussion of meteorological events (including volcanic ash cloud) causing or
expecting to impact the flow of air traffic across an ARTCC.
Tools
GFA Tool G Interactive website that includes SIGMETs and CWAs for volcanic ash cloud
when they are in effect.
Flight Service
Interactive Map G Interactive website that includes SIGMETs and CWAs for volcanic ash cloud
when they are in effect.
3.4.2.11 Products with Tropical Cyclone Information
Table 3-14. Weather Element: Tropical Cyclone (e.g., Hurricane)
Type: text (T), graphic (G), image (I), voice (V)
Tropical Cyclone
Information
Contained In:
Type Summary
Observations
Radar I Tropical cyclones are visible on radar when in range.
Satellite I Tropical cyclones are visible on satellite.
Analysis
Surface Analysis
Chart G Tropical cyclones are included using standard symbols.
Advisories
Convective
SIGMET T, G Issued for thunderstorms associated with tropical cyclones.
SIGMET T, G SIGMETs are issued for tropical cyclones except over the CONUS and
associated coastal waters.
Chapter 3, Overview of Aviation Weather Information 3-26
Tropical Cyclone
Information
Contained In:
Type Summary
TCA T, G TCAs are issued four times daily and report the current and forecast tropical
cyclone position and intensity.
Forecasts
Medium-Level
SIGWX G Tropical cyclones are included using standard symbols.
High-Level SIGWX G Global forecasts that include tropical cyclones using standard symbols.
Surface Prog Charts G Tropical depressions, tropical storms, and hurricanes are included using
symbols.
AFD T May include a discussion on tropical cyclones when applicable.
MIS T A nontechnical discussion of meteorological events (including tropical cyclones)
causing or expecting to impact the flow of air traffic across an ARTCC.
Tools
GFA Tool G Interactive website that includes tropical cyclones, if applicable.
Flight Service
Interactive Map G Interactive website that includes tropical cyclones, if applicable.
3.4.2.12 Products with Sandstorm/Dust Storm Information
Table 3-15. Weather Element: Sandstorm/Dust Storm
Type: text (T), graphic (G), image (I), voice (V)
Sandstorm/Dust
Storm Information
Contained In:
Type Summary
Observations
METAR and SPECI
(ASOS, AWOS,
ATIS)
T, G,
SS, DS, BLDU, and BLSA are reported in manual observations, at some
augmented observations, but not automated observations. Automated
observations may report these as HZ.
PIREP T, G,
V Included if reported.
Radar I Potentially visible on radar.
Satellite I Sandstorms/dust storms may be visible on satellite if not obscured by cloud
cover.
Advisories
SIGMET T, G Widespread sandstorms/dust storms (WDSPR DS, WDSPR SS) are conditions
that trigger the issuance of a SIGMET.
CWA T, G One of the conditions that triggers the issuance of a CWA.
Forecasts
TAF T, G Included as BLDU, BLSA, DRDU, and DRSA.
Aviation Surface
Forecast G Derived from the GFA and includes forecasts of obscurations such as
sandstorms/dust storms.
Low-Level SIGWX G Could be inferred when IFR or MVFR conditions are depicted in desert areas
and supported by other products (e.g., METAR, TAF, SIGMET).
Chapter 3, Overview of Aviation Weather Information 3-27
Sandstorm/Dust
Storm Information
Contained In:
Type Summary
AFD T May include a discussion on current or forecast sandstorms/dust storms when
applicable.
Tools
Graphical Forecasts
for Aviation (GFA)
Tool
G Interactive website that includes sandstorms/dust storms, if applicable.
Flight Service
Interactive Map G Interactive website that includes sandstorms/dust storms, if applicable.
3.4.2.13 Products with Mountain Obscuration Information
Table 3-16. Weather Element: Mountain Obstruction
Type: text (T), graphic (G), image (I), voice (V)
Mountain
Obscuration
Information
Contained In:
Type Summary
Observations
METAR, SPECI
(ASOS, AWOS,
ATIS)
T, V
May be included in RMK section at some mountain airports. At times it may be
inferred or implied by the reporting of clouds at ASOS/AWOS located in
mountain passes.
PIREP T, G,
V Included when reported.
Weather Camera I Mountain obscuration may be visible on the camera.
Advisories
AIRMET T, G AIRMET Sierra are issued when widespread mountain obstruction is occurring
or expected to occur.
Forecasts
Aviation Clouds
Forecast G Part of the derived forecasts from the GFA and includes overlays of mountain
obscuration when applicable.
Alaska Area
Forecast T A description of significant clouds and weather including mountain obscuration.
AFD T May include a discussion on current or forecast mountain obscuration.
Tools
GFA Tool G Interactive website that includes mountain obscuration, if applicable.
Flight Service
Interactive Map G Interactive website that includes mountain obscuration, if applicable.
3.4.2.14 Products with Surface-Based IFR Information
For most aviation weather products, IFR refers to ceilings less than 1,000 feet (ft) (i.e., above ground level
(AGL)) and/or surface visibilities less than 3 statute miles ( SM). But many aviation weather websites
provide a graphical depiction of METAR s or Aviation Selected Special Weather Reports ( SPECI), and
sometimes TAFs, using color -coded station plots for various Weather Flight Categories. These Weather
Chapter 3, Overview of Aviation Weather Information 3-28
Flight Categories and color codes serve as a means to help pilots visually assess ceilings and visibilities on
a map of METARs. Most aviation weather websites use the following color codes and definitions for their
display of METARs/SPECIs (and sometimes TAFs) on their website:
• Purple: LIFR = Low IFR, ceilings less than 500 ft and/or visibilities less than 1 SM.
• Red: IFR = Ceiling 500 ft to less than 1,000 ft and/or visibility 1 SM to less than 3 SM.
• Blue: MVFR = Ceiling 1,000 to 3,000 ft and/or visibility 3 to 5 SM.
• Green: VFR = Ceiling greater than 3,000 ft and visibility greater than 5 SM.
Note: The VFR Weather Flight Category is not to be confused with the basic VFR weather minimums
given in 14 CFR § 91.155. Weather Flight Categories are only intended for situational awareness.
Table 3-17. Weather Element: Surface IFR
Type: text (T), graphic (G), image (I), voice (V)
Surface IFR
Information
Contained In:
Type Summary
Observations
METAR and SPECI
(ASOS, AWOS,
ATIS)
T, G,
Ceiling less than 1,000 ft and/or visibility less than 3 SM.
Note: Websites may graphically depict METAR/SPECI as IFR when ceilings are
from 500 ft to less than 1,000 ft and/or visibility 1 SM to less than 3 SM.
Analysis
Advisories
AIRMET T, G AIRMET Sierra is issued when surface-based IFR conditions are occurring or
expected to occur.
CWA T, G May be issued if conditions are at or approaching LIFR conditions (ceilings less
than 500 ft and/or visibilities less than 1 SM).
Forecasts
TAF T, G
Ceiling less than 1,000 ft and/or visibility less than 3 SM.
Note: Websites may graphically depict TAFs as IFR when ceilings are from
500 ft to less than 1,000 ft and/or visibility 1 SM to less than 3 SM.
Aviation Surface
Forecast G Derived from NOAA’s GFA and includes forecasts of surface IFR at specified
valid times.
Alaska Area
Forecast T A 12- to 18-hour categorical outlook for IFR is included in the description of
significant clouds and weather.
Hawaii Area
Forecast T A 12- to 18-hour categorical outlook for IFR is included in the description of
significant clouds and weather.
Gulf of America and
Caribbean Area
Forecast
T A 12- to 24-hour categorical outlook for IFR is included in the description of
significant clouds and weather.
Low-Level SIGWX G Areas of forecast IFR conditions are depicted.
Alaska SIGWX G Areas of forecast IFR conditions are depicted.
AFD T Describes weather conditions such as surface IFR as they relate to the TAF and
provide additional aviation weather-related issues.
Chapter 3, Overview of Aviation Weather Information 3-29
Surface IFR
Information
Contained In:
Type Summary
MIS T A nontechnical discussion of meteorological events (including surface IFR)
causing or expecting to impact the flow of air traffic across an ARTCC.
Tools
GFA Tool G Interactive website that includes observed and forecast IFR, including AIRMET
for IFR.
Flight Service
Interactive Map G Interactive website that includes METAR and TAF station plots depicting
surface-based IFR conditions. AIRMETs for IFR are also shown.
3.4.2.15 Products with Surface-Based MVFR Information
MVFR is a Weather Flight Category. While the “R” in the acronym means “rules,” there are no 14 CFR
part 91 MVFR weather minimums. The MVFR weather category is defined as ceilings from 1,000 ft to and
including 3,000 ft (AGL), and/or surface visibilities from 3 SM to and including 5 SM.
Table 3-18. Surface MVFR
Type: text (T), graphic (G), image (I), voice (V)
Surface MVFR
Information
Contained In:
Type Summary
Observations
METAR and SPECI
(ASOS, AWOS,
ATIS)
T, G,
Ceiling 1,000 ft to 3,000 ft (inclusive) and/or visibility 3 SM to 5 SM
(inclusive). Graphical depictions may provide color-coded flight categories,
including MVFR.
Analysis
Advisories
Forecasts
TAF T, G
Ceiling 1,000 ft to 3,000 ft (inclusive) and/or visibility 3 SM to 5 SM
(inclusive). Graphical depictions may provide color-coded MVFR flight
categories for the TAF.
Alaska Area
Forecast T A 12- to 18-hour categorical outlook for MVFR is included in the description of
significant clouds and weather.
Hawaii Area
Forecast T A 12- to 18-hour categorical outlook for MVFR is included in the description of
significant clouds and weather.
Gulf of America and
Caribbean Area
Forecast
T A 12- to 24-hour categorical outlook for MVFR is included in the description of
significant clouds and weather.
Low-Level SIGWX G Areas of forecast MVFR conditions are depicted.
Alaska SIGWX G Areas of forecast MVFR conditions are depicted.
AFD T Describes weather conditions such as surface MVFR as they relate to the TAF
and provide additional aviation weather-related issues.
Tools
GFA Tool G Interactive website that includes observed and forecast MVFR.
Flight Service
Interactive Map G Interactive website that includes METAR and TAF station plots depicting
MVFR conditions.
Chapter 3, Overview of Aviation Weather Information 3-30
3.4.2.16 Products with Cloud Coverage Information
Table 3-19. Weather Element: Cloud Coverage
Type: text (T), graphic (G), image (I), voice (V)
Cloud Coverage
Information
Contained In:
Type Summary
Observations
METAR, SPECI
(ASOS, AWOS,
ATIS)
T, G,
V Cloud coverage is included.
PIREP T, G,
V Includes sky condition such as cloud coverage when reported.
Satellite I A general cloud coverage can be inferred from satellite.
Weather Camera I Clouds over the horizon can be seen if in view of the camera and there is
sufficient daylight. Overhead clouds cannot be seen.
Analysis
Surface Analysis
Charts G Cloud coverage amounts are included within the station plot models and can be
inferred when charts are combined with satellite imagery.
Advisories
AIRMET T, G Issued for areas of IFR ceilings and/or visibilities (i.e., BKN or OVC less than
1,000 ft and/or 3 SM).
Forecasts
TAF T, G Cloud coverage is included.
Aviation Clouds
Forecast G Part of the derived forecasts from the GFA and includes cloud coverage.
Alaska Area
Forecast T Cloud coverage is included.
Hawaii Area
Forecast T Cloud coverage is included.
Gulf of America and
Caribbean Area
Forecast
T Cloud coverage is included.
Low-Level SIGWX G
Depicts forecasts areas of IFR ceilings and/or visibilities (i.e., BKN or OVC less
than 1,000 ft and/or less than 3 SM) as well as MVFR (i.e., BKN or OVC from
1,000 ft to 3,000 ft and/or 3 SM to 5 SM).
Alaska SIGWX G Areas of forecast IFR and MVFR conditions are depicted.
Cloud Top Forecast G Computer model cloud amount and height of cloud tops.
AFD T May include a discussion on current or forecast cloud cover.
Tools
GFA Tool G, I Interactive website that includes cloud coverage overlay, METAR station plots,
and satellite imagery.
Flight Service
Interactive Map G, I Interactive website that includes METAR station plots and satellite imagery.