CHAPTER 4
ASPEN ADS
-B IN
ADS-B Pilot’s Guide
Page 4-16
091-00057-001 REV A
4.4.3 AIRMET / SIGMET
The EFD 1000/500 MFD displays AIRMET/SIGMET graphical depiction of AIRMETs
(AIRman’s METeorological Information) and SIGMETs (SIGnificant METeorological
Information). AIRMETs and SIGMETs are weather advisories broadcast by National
Weather Service for the lower 48 states and adjacent coastal waters. Both AIRMETs
and SIGMETs warn pilots of potentially hazardous weather. AIRMETS warn of less
severe weather than SIGMETs. The AIRMET/SIGMET screen displays these advisories as
graphical images overlaid on the basic weather map.
There are three AIRMET types: S (sierra) for mountain obscuration and IFR conditions,
T (tango) for turbulence, and Z (zulu) for icing. They are all issued for six hour periods
beginning at 0245 UTC, and are amended when necessary for changing weather
conditions or issuance/cancellation of a SIGMET. See Table 4-5 for a description and
definition of AIRMET/SIGMET symbology.
There are two types of SIGMETs, non-convective and convective. Non-convective
SIGMETs warn about severe Icing, extreme turbulence, dust storms and/or sandstorms
lowering visibilities to less than three (3) miles, and volcanic ash. Convective SIGMETS
are issued hourly for thunderstorm-related aviation hazards. SIGMETS are issued for 6
hour periods for conditions associated with hurricanes and 4 hours for all other events.
If conditions persist beyond the forecast period, the SIGMET is updated and reissued.
Table 4-5
AIRMET / SIGMET Symbology