All remarks and additive data groups used in an
METAR coded observation must be indicated by the
abbreviation "RMK" and should be in the order listed in
table 3-3. Some general comments on certain remarks
appear below.
SEA LEVEL PRESSURE (SLPppp). This
remark is MANDATORY. Sea level pressure is
encoded as SLPppp where SLP is the remark identifier
and ppp is the sea-level pressure coded by using the
tens, units, and tenths digits in hectopascals. For
example, a sea level pressure of 998.2 hectopascals
would be encoded as "SLP982." If sea level pressure is
not available, it is coded as "SLPNO."
AIRCRAFT MISHAP (ACFT MSHP). If a report
is taken to document weather conditions when notified
of an aircraft mishap, the remark ACFT MSHP will be
included on the observation form but will not be
transmitted.
Table 3-4.—Additive Data Groups
Additive Data (RMK)
Element
METAR SPECI
Hourly Precipitation
X
Amount
3- and 6-hourly Precipitation
X
Amount
24-hour Precipitation
X
Amount
Snow Depth on the Ground,
X
4/sss
Water Equivalent of Snow on
X
the ground, 933RRR
Cloud Types 8/CLCMCH
X
Hourly Temperature and
X
Dew Point
6-Hourly Maximum
X
Temperature
6-Hourly Minimum
X
Temperature
24-Hour Maximum and
X
Minimum Temperature
3-Hour Pressure Tendency
X
5appp
X indicates element included
at all stations
FIRST and LAST (FIRST and LAST). At part-
time stations, the first and last reports transmitted will
be identified by including the word "FIRST" in the
report of the day after a break in observing coverage
and/or the word "LAST" in the last report of the day
before a break in observation coverage.
Additive Data Groups
Additive data consists of supplementary
precipitation, temperature, cloud, and pressure
information reported hourly, every 3 hours or every 6
hours. At 0300Z, 0900Z, 1500Z, and 2100Z, the 3-
hourly additive data is included in observation reports.
At 0000Z, 0600Z, 1200Z, and 1800Z, the 6-hourly
additive data is included in the observation reports.
The 3-hourly additive data consists of the 3-hour
pressure tendency, cloud type information, and
precipitation data reported in the symbolic format
shown in table 3-4. The 6-hourly additive data shown in
this table is identical except it contains 6-hour
precipitation data.
3-10
Other supplementary information consists of snow
depth, maximum or minimum temperature, and 24-hour
precipitation. The snow depth group is reported (in
inches) only if there is snow or frozen precipitation on
the ground. It is normally reported in the OOOOZ and
1200Z observations, and at subsequent 6-hourly
observations (18002, OOOOZ, 06002) if measurable
precipitation has occurred during those periods. The
maximum and minimum temperatures during the past 6
hours are reported at 0000Z, 0600Z, 1200Z, and 1800Z,
while maximum and minimum temperatures during the
past 24 hours are reported at 0600Z. The 24-hour
precipitation (liquid equivalent) is reported only at
1200Z. If a station is closed down for a weekend or
holiday, the 24-hour precipitation should also be used to
report total precipitation since the last reported 24-hour
precipitation In this case, the 24-hour precipitation may
actually be used to report a 72-hour total precipitation.
Runway Conditions
Runway surface condition (RSC) and average
runway condition reading (RCR) are included in a
METAR coded report when runway conditions produce
less than normal braking for landing aircraft. Different
codes may be combined to describe conditions. Each
condition should be followed by a decelerometer
reading (RCR) from 02, poor braking action, to 25,
excellent braking action. Codes used for RSC include
"WR" for wet runway, "SLR" for slush on runway,
