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Aeronautical Information Manual (AIM), page 506

Index   505 -- Page 506 -- 507

7110.65R
AIM CHG 2



8. Weather Phenomena. The weather as
reported in the METAR code represents a significant
change in the way weather is currently reported. In
METAR, weather is reported in the format:

Intensity/Proximity/Descriptor/Precipitation/

Obstruction to visibility/Other

NOTE-
The "/" above and in the following descriptions (except as
the separator between the temperature and dew point) are

for separation purposes in this publication and do not
appear in the actual METARs.


(a) Intensity applies only to the first type of
precipitation reported. A "-" denotes light, no symbol
denotes moderate, and a "+" denotes heavy.

(b) Proximity applies to and reported only
for weather occurring in the vicinity of the airport
(between 5 and 10 miles of the point(s) of
observation). It is denoted by the letters "VC."
(Intensity and "VC" will not appear together in the
weather group).

(c) Descriptor. These eight descriptors ap-
ply to the precipitation or obstructions to visibility:
TS . . . . . . . . . . . thunderstorm
DR . . . . . . . . . . . low drifting
SH . . . . . . . . . . . showers
MI . . . . . . . . . . . shallow
FZ . . . . . . . . . . . freezing
BC . . . . . . . . . . . patches
BL . . . . . . . . . . . blowing
PR . . . . . . . . . . . partial

NOTE-
Although "TS" and "SH" are used with precipitation and

may be preceded with an intensity symbol, the intensity still
applies to the precipitation, not the descriptor.

(d) Precipitation. There are nine types of
precipitation in the METAR code:
RA . . . . . . . . . . rain
DZ . . . . . . . . . . drizzle
SN . . . . . . . . . . snow
GR . . . . . . . . . . hail (1/4" or greater)
GS . . . . . . . . . . small hail/snow pellets
PL . . . . . . . . . . ice pellets
SG . . . . . . . . . . snow grains
IC . . . . . . . . . . . ice crystals (diamond dust)
UP . . . . . . . . . . unknown precipitation
(automated stations only)

3/15/07
5/26/16
12/10/15

(e) Obstructions to visibility. There are
eight types of obscuration phenomena in the METAR
code (obscurations are any phenomena in the
atmosphere, other than precipitation, that reduce
horizontal visibility):

FG . . . . . . . . . . fog (vsby less than 5/8 mile)

HZ . . . . . . . . . . haze
FU . . . . . . . . . . smoke
PY . . . . . . . . . . spray

BR . . . . . . . . . . mist (vsby 5/8 - 6 miles)

SA . . . . . . . . . . sand
DU . . . . . . . . . . dust
VA . . . . . . . . . . volcanic ash

NOTE-
Fog (FG) is observed or forecast only when the visibility is
less than five-eighths of mile, otherwise mist (BR) is
observed or forecast.

(f) Other. There are five categories of other
weather phenomena which are reported when they
occur:
SQ . . . . . . . . . . . squall
SS . . . . . . . . . . . sandstorm
DS . . . . . . . . . . . duststorm
PO . . . . . . . . . . dust/sand whirls
FC . . . . . . . . . . . funnel cloud
+FC . . . . . . . . . tornado/waterspout

Examples:

TSRA . . . . . . . . . thunderstorm with moderate
rain
+SN . . . . . . . . . . heavy snow
-RA FG . . . . . . . light rain and fog

BRHZ . . . . . . . . mist and haze

(visibility 5/8 mile or greater)
FZDZ . . . . . . . . . freezing drizzle
VCSH . . . . . . . . rain shower in the vicinity
+SHRASNPL . . heavy rain showers, snow,
ice pellets (intensity
indicator refers to the
predominant rain)

9. Sky Condition. The sky condition as
reported in METAR represents a significant change
from the way sky condition is currently reported. In
METAR, sky condition is reported in the format:

Amount/Height/(Type) or Indefinite Ceiling/Height


7-1-62 Meteorology

Page 506 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   505 -- Page 506 -- 507