AMOFSG/10-SoD
Appendix C
APPENDIX C DRAFT
DRAFT AMENDMENT TO ANNEX 3 —
METEOROLOGICAL SERVICE FOR INTERNATIONAL AIR NAVIGATION
(EIGHTEENTH EDITION — JULY 2013)
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ATTACHMENT C. SELECTED CRITERIA APPLICABLE TO
AERODROME REPORTS
(The guidance in this table relates to Chapter 4 and Appendix 3.)
Surface wind
Speed
variations3
Directional variations3
≥ 60° and < 180°
Specifications
Mean speed
< 1.5 m/s
(3 kt)
Local routine
and special
report
METAR/
SPECI
Relevant
reporting
scales for all
messages
2/10
min
≥ 180°
≥ 1.5 m/s
(3 kt)
2/10
min
7
7
2 min
Exceeding
the
mean speed
by ≥ 5 m/s
(10 kt)
10
min
8
VRB + 2
extreme
directions8
mean + 2
extreme
directions8
VRB (no
extremes)8
10
min
10
min
10
min
10
min
VRB (no
extremes)
Maximum
speed8
VRB (no
extremes)
mean + 2
extreme
directions
Minimum and
maximum
speed
8
Direction in three figures
rounded off to the
nearest 10 degrees
Speed in
1 m/s
or 1 kt
(degrees 1 – 4 down,
degrees 5 – 9 up)
Speed <
0.5 m/s (1 kt)
indicated as
CALM
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AMOFSG/10-SoD
Appendix C
C-2
Notes.—
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3.
Considered for the past 10 minutes (exception: if the 10-minute period includes a marked discontinuity (i.e. the direction changes ≥ 30°
with a speed ≥ 5 m/s or the speed changes ≥ 5 m/s lasting ≥ 2 minutes), only data after the discontinuity to be used).
...
7.
8.
Time averaging, for mean values and, if applicable, referring period for extreme values, indicated in the upper left-hand corner.
According to the WMO Manual on Codes (WMO-No. 306), Volume I.1, Part A — Alphanumeric Codes, paragraph 15.5.5, “it is
recommended that the wind measuring systems should be such that peak gusts should represent a three-second average”.
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