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b) Practices do not require SPEC1 for increases of mean surface wind speed.
C) Practices require SPEC1 for squall, where squall is defined as a strong wind characterized by a
sudden onset in which the wind speed increases by at least 16 kt and is sustained at 22 kt or more
for at least one minute.
d) Practices do not require SPEC1 for wind direction changes based on local criteria.
f) SPEC1 not prepared for the equivalents in feet of 150, 350 and 600 m. United States military
stations may not report a SPECI based on RVR. SPECI is made when the highest value from the
designated RVR runway decreases to less than, or if below, increases to equal or exceed, 2 400 ft
during the preceding 10 minutes.
g) Practices do not require SPEC1 for the onset, cessation or change in intensity of: freezing fog;
h) moderate or heavy precipitation (including showers thereof); low drifting dust, sand or snow;
blowing dust, sand or snow (including snowstorm); duststorm or sandstorm. SPECI is made when
referenced weather phenomena cause changes in the visibility, ceiling or sky condition which meet
criteria for SPECI.
i) Practices do not require SPEC1 when the height of the lowest BKN or OVC cloud layer or vertical
j) visibility changes to or passes 100 ft (30 m) unless an approach minimum exists. SPEC1 is made
when the ceiling (rounded off to reportable values) forms or dissipates below, decreases to less
than, or if below, increases to equal or exceed, 3 000, 1 500, 1 000 and 500 ft, the lowest standard
instrument approach procedure minimum published in the National Ocean Survey (NOS) U.S.
Terminal Procedures. If none published, then 200 ft.
The United States does not provide wind observations for specific runways but wind
representative for the airport. The surface wind for each sensor in the meteorological station is not
displayed. NWS Weather Forecast Offices have access to the METAIUSPECI reports.
4.1.3.1 b) Practice is to provide a 2-minute average wind observation for the METARISPECI.
* Recommended Practice
Table A3-2
APPENDIX 4
3.1.4
The wind direction may be considered variable if, during the Zminute evaluation period, the wind
speed is 6 kt or less. Also, the wind direction shall be considered variable if, during the 2-minute
evaluation period, it varies by 60' or more when the wind speed is greater than 6 kt.
Practices define wind gust as rapid fluctuations in wind speed with a variation of 10 kt or more
between peaks and lulls. Wind speed data for the most recent 10 minutes are examined and a gust,
the maximum instantaneous wind speed during that 10-minute period, is reported if the definition
above is met during that period.
Practice is to report RVR in increments of 100 ft up to 1 000 ft, increments of 200 ft from 1 000 ft
to 3 000 ft, and increments of 500 ft above 3 000 ft to 6 000 ft.
Practice is to report RVR for a single designated runway in the METARISPECI. RVR tendency is
not reported.
The practice is not to report the following weather phenomena in METAR or SPECI: DZ, PL, IC,
SG, GR, GS, SA, DU, FU, VA, PY, PO, SQ, FC, DS and SS, at unstaffed stations.
The practice is not to report the following characteristics of present weather phenomena in
METAR or SPECI: SH, DR, MI, BC and PR, at unstaffed stations.
The practice with respect to the proximity indicator VC is between 5 to 10 statute miles from the
point of observation with the exception of precipitation for which VC indicates > 0 to 10 statute
miles from the point of observation.
The United States reports only up to 3 layers at automated sites and up to 6 layers at manual sites.
Cloud layer amounts are a summation of layers at or below a given level, utilizing cumulative
cloud amount. In addition, at automated sites which are unstaffed, cloud layers above 12 000 ft are
not reported. At staffed automated sites, clouds above 12 000 ft may be augmented. CAVOK,
SKC and NSC are not used.
The United States has a remarks section that provides similar information.
Wind shear is not included in the remarks section of METARISPECI.
The term "no directional variations" (NDV) is not used.
The symbol "///" when used in the cloud section of the METAR refers to a mountain station where
the layer is below the station level. "NCD" when no clouds can be observed is not used.
The field d) is also used to denote a correction to the METARISPECI by "COR
MWOs do not disseminate special air-reports.
* Recommended Practice
APPENDIX 5
1.1
APPENDIX 6
1.1.3
At selected military aerodromes, practices are to forecast for the 5 and 6 groups, turbulence and
icing and the lowest expected altimeter setting.
Forecast visibility increments used consist of 114 mile from 0 (zero) to 1 mile, 112 mile from 1 to
　
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