AIM
5/19/22
users. FIG 7
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1 provides conversion tables for the
b.
The FAA maintains an extensive surface
most used weather elements that will be encountered
weather observing program. Airport observations
by pilots.
(METAR and SPECI) in the U.S. are provided by
automated observing systems. Various levels of
human oversight of the METAR and SPECI reports
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2. FAA Weather Services
and augmentation may be provided at select larger
a.
The FAA provides the Flight Service program,
airports by either government or contract personnel
which serves the weather needs of pilots through its
qualified to report specified weather elements that
flight service stations (FSS) (both government and
cannot be detected by the automated observing
contract via 1-800-WX-BRIEF) and via the Internet,
system. The requirements to issue SPECI reports are
through Leidos Flight Service.
detailed in TBL 7
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TBL 7
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SPECI Issuance Table
1
Wind Shift
Wind direction changes by 45
°
or more, in less than 15 minutes, and the wind speed is
10 kt or more throughout the wind shift.
2
Visibility
The surface visibility (as reported in the body of the report):
Decreases to less than 3 sm, 2 sm, 1 sm,
½
sm,
¼
sm or the lowest standard instrument
approach procedure (IAP) minimum.
1
Increases to equal to or exceed 3 sm, 2 sm, 1 sm,
½
sm,
¼
sm or the lowest standard
IAP minimum.
1
1
As published in the U.S. Terminal Procedures. If none published, use
½
sm.
3
RVR
The highest value from the designated RVR runway decreases to less than 2,400 ft during
the preceding 10 minutes; or, if the RVR is below 2,400 ft, increases to equal to or exceed
2,400 ft during the preceding 10 minutes. U.S. military stations may not report a SPECI
based on RVR.
4
Tornado, Funnel
Cloud, or
Waterspout
Is observed.
Disappears from sight or ends.
5
Thunderstorm
Begins (a SPECI is not required to report the beginning of a new thunderstorm if one
is currently reported).
Ends.
6
Precipitation
Hail begins or ends.
Freezing precipitation begins, ends, or changes intensity.
Ice pellets begin, end, or change intensity.
Snow begins, ends, or changes intensity.
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Squalls
When a squall occurs. (Wind speed suddenly increases by at least 16 knots and is
sustained at 22 knots or more for at least one minute.)
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Meteorology