Chapter 3, Overview of Aviation Weather Information 3-31
3.4.2.17 Products with Cloud Base Information
Table 3-20. Weather Element: Cloud Base
Type: text (T), graphic (G), image (I), voice (V)
Cloud Base
Information
Contained In:
Type Summary
Observations
METAR, SPECI
(ASOS, AWOS,
ATIS)
T, G,
V Cloud bases included when reported.
PIREP T, G,
V Includes cloud bases when reported.
Weather Camera I Cloud bases are difficult to estimate or impossible to determine from a camera.
Analysis
Surface Analysis
Charts G Some surface analysis charts may plot the height of a BKN or OVC ceiling.
Advisories
AIRMET G Issued for areas of IFR ceilings and/or visibilities (i.e., BKN or OVC less than
1,000 ft and/or less than 3 SM).
CWA T, G May be issued for ceilings less than 500 ft.
Forecasts
TAF T, G Cloud bases included.
Aviation Cloud
Forecast G Part of the derived forecasts from GFA and includes cloud bases.
Alaska Area
Forecast T Cloud bases included.
Hawaii Area
Forecast T Cloud bases included.
Gulf of America and
Caribbean Area
Forecast
T Cloud bases included.
Low-Level SIGWX G
Depicts forecast 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.
AFD T May include a discussion on current or forecast cloud bases and/or IFR,
MVFR, etc. conditions.
MIS T May include a discussion on current or forecast IFR conditions.
Tools
GFA Tool G Interactive website that includes overlay of forecast cloud bases as well as
METAR station plots.
Flight Service
Interactive Map G Interactive website that includes METAR station plots.
Chapter 3, Overview of Aviation Weather Information 3-32
3.4.2.18 Products with Cloud Tops Information
Table 3-21. Weather Element: Cloud Tops
Type: text (T), graphic (G), image (I), voice (V)
Cloud Tops
Information
Contained In:
Type Summary
Observations
PIREP T, G,
V Cloud tops included when reported.
Analysis
Advisories
Convective
SIGMET T, G CB cloud tops are included in Convective SIGMETs.
SIGMET T, G CB cloud tops are included in SIGMETs for thunderstorms (outside the
CONUS).
Forecasts
Aviation Cloud
Forecast G Part of the derived forecasts from the GFA and includes cloud tops. This product
provides a forecast of cloud coverage and height (in hundreds of feet MSL).
Alaska Area
Forecast T A description of significant clouds and weather for the first 12 hours; includes
cloud tops.
Hawaii Area
Forecast T A description of significant clouds and weather for the first 12 hours; includes
cloud tops.
Gulf of America and
Caribbean Area
Forecast
T A description of significant clouds and weather for the first 12 hours; includes
cloud tops.
Medium-Level
SIGWX G Forecast height of CB tops included.
High-Level SIGWX G Global forecasts that include forecast CB tops.
Cloud Top Forecast I Computer model cloud amount and height of cloud tops.
TCF G The TCF includes forecast CB tops.
Tools
GFA Tool G Interactive website that includes overlay of forecast cloud tops.
Chapter 3, Overview of Aviation Weather Information 3-33
3.4.2.19 Products with Cloud Layers Information
Table 3-22. Weather Element: Cloud Layers
Type: text (T), graphic (G), image (I), voice (V)
Cloud Layers
Information
Contained In:
Type Summary
Observations
METAR, SPECI,
(ASOS, AWOS,
ATIS)
T, G,
V Reports the sky condition including cloud layers.
PIREP/AIREP T, G,
V PIREPs may include cloud layers.
Analysis
Advisories
Forecasts
TAF T, G Cloud layers are included.
Aviation Cloud
Forecast G Part of the derived forecasts from GFA and includes cloud layers.
Alaska Area
Forecast T A description of cloud layers is included.
Hawaii Area
Forecast T A description of cloud layers is included.
Gulf of America and
Caribbean Area
Forecast
T A description of cloud layers is included.
Tools
GFA Tool G Interactive website that includes overlay of forecast cloud layers as well as
METAR station plots.
Flight Service
Interactive Map G Interactive website that includes METAR station plots.
3.4.2.20 Products with Pressure Information
Table 3-23. Weather Element: Pressure
Type: text (T), graphic (G), image (I), voice (V)
Pressure
Information
Contained In:
Type Summary
Observations
METAR, SPECI
(ASOS, AWOS,
RTMA, ATIS)
T, G,
Altimeter setting is included. Sea level pressure included in the RMK section of
the METAR.
Analysis
Surface Analysis
Chart G Sea level pressure is depicted as isobars and within the station plots. High- and
low-pressure centers are also shown.
Chapter 3, Overview of Aviation Weather Information 3-34
Pressure
Information
Contained In:
Type Summary
Advisories
Forecasts
Surface Prog Charts G Sea level pressure is depicted as isobars. High- and low- pressure centers
depicted.
Tools
3.4.2.21 Products with Fronts Information
Table 3-24. Weather Element: Fronts
Type: text (T), graphic (G), image (I), voice (V)
Fronts Information
Contained In: Type Summary
Observations
METAR, SPECI
(ASOS, AWOS,
ATIS)
T, G,
Manually produced METARs and SPECIs may report “FROPA” in the RMK
portion.
Analysis
Surface Chart
Analysis G Depicts the location of fronts as well as the high- and low-pressure systems.
Advisories
Forecasts
TAF T
Fronts are not explicitly mentioned under weather phenomena, but a significant
change in wind direction coupled with changes in other elements can imply a
forecast frontal passage.
Alaska Area
Forecast T There is a brief discussion of the synoptic weather affecting the region during
the first 18-hour valid period, which could include frontal boundaries.
Hawaii Area
Forecast T There is a brief discussion of the synoptic weather affecting the region during
the first 18-hour valid period, which could include frontal boundaries.
Gulf of America and
Caribbean Area
Forecast
T There is a brief discussion of the synoptic weather affecting the region during
the entire 24-hour valid period, which could include frontal boundaries.
Alaska SIGWX G Pressure systems and fronts are included using standard symbols.
Alaska Surface
Chart G Fronts are depicted using standard symbols for this chart. This product is issued
every six hours with forecasts valid for 00Z, 06Z, 12Z, and 18Z.
Surface Prog Charts G Fronts are included using standard symbols.
AFD T May include a discussion on fronts when applicable.
Tools
Chapter 3, Overview of Aviation Weather Information 3-35
3.4.2.22 Products with Temperature Information
Table 3-25. Weather Element: Temperature
Type: text (T), graphic (G), image (I), voice (V)
Temperature Aloft
Information
Contained In:
Type Summary
Note: Temperatures are in degrees Celsius (°C)
Observations
METAR, SPECI
(ASOS, AWOS,
ATIS)
T, G,
V Surface temperature is included.
PIREP/AIREP T, G,
V Temperature aloft is included if reported.
Analysis
Upper Air Analysis T, G At select pressure levels, the wind direction and speed are displayed in tens of
degrees and wind speed is in knots.
Freezing Level
Analysis G
Temperatures aloft can be indicated with limitations. Depicts the freezing level
at the lowest altitude in the atmosphere over a given location at which the air
temperature reaches 0 °C.
RTMA T Surface temperature is included.
Advisories
Forecasts
Winds and
Temperature Aloft T, G
The text format provides the temperature aloft in a coded format for select
height levels and locations. Graphical format provides contours of temperatures
aloft.
Low-Level SIGWX G Temperatures aloft can be indicated with limitations. Multiple freezing levels
can be forecast when temperatures are 0 °C at more than one altitude aloft.
WAFS G Global forecasts include temperatures aloft, at selected height levels, from
model data in a grid point format.
Upper Air Forecasts G Computer model outputs for temperatures aloft at select height levels (available
levels vary depending on the model). Depicted using contours (isotherms).
Tools
3.4.2.23 Products with Space Weather Information
Table 3-26. Weather Element: Space Weather
Type: text (T), graphic (G), image (I), voice (V)
Space Weather
Information
Contained In:
Type Summary
Observations
(See Space Weather Advisory)
Analysis
Chapter 3, Overview of Aviation Weather Information 3-36
Space Weather
Information
Contained In:
Type Summary
Advisories
Space Weather
Advisory T
Issued whenever space weather conditions exceed predefined ICAO thresholds
for both moderate and severe impacts. Provides an observed or expected
location for the impact and 6-, 12-, 18-, and 24-hour forecasts.
Forecasts
(See Space Weather Advisory)
Tools
3.4.2.24 Products with Density Altitude Information
Table 3-27. Weather Element: Density Altitude
Type: text (T), graphic (G), image (I), voice (V)
Density Altitude
Information
Contained In:
Type Summary
Observations
ASOS, AWOS, and
ATIS V
Included in the ASOS and AWOS broadcasts (phone and radio) when density
altitude exceeds the field elevation by more than 1,000 ft. A density altitude
advisory (i.e., “check density altitude”) is broadcast on ATIS when appropriate.
Analysis
Advisories
Forecasts
Tools
Part 2: