AIM
4/3/14
7−1−64
Meteorology
5. Wind.
The wind is reported as a five digit
group (six digits if speed is over 99 knots). The first
three digits are the direction the wind is blowing
from, in tens of degrees referenced to true north, or
“VRB” if the direction is variable. The next two digits
is the wind speed in knots, or if over 99 knots, the next
three digits. If the wind is gusty, it is reported as a “G”
after the speed followed by the highest gust reported.
The abbreviation “KT” is appended to denote the use
of knots for wind speed.
EXAMPLE
−
13008KT
− wind from 130 degrees at 8 knots
08032G45KT
− wind from 080 degrees at 32 knots with
gusts to 45 knots
VRB04KT
− wind variable in direction at 4 knots
00000KT
− wind calm
210103G130KT
− wind from 210 degrees at 103 knots with
gusts to 130 knots
If the wind direction is variable by 60 degrees or more and
the speed is greater than 6 knots, a variable group
consisting of the extremes of the wind direction separated
by a “v” will follow the prevailing wind group.
32012G22KT 280V350
(a) Peak Wind.
Whenever the peak wind
exceeds 25 knots “PK WND” will be included in
Remarks, e.g., PK WND 28045/1955 “Peak wind two
eight zero at four five occurred at one niner five five.”
If the hour can be inferred from the report time, only
the minutes will be appended, e.g., PK WND
34050/38 “Peak wind three four zero at five zero
occurred at three eight past the hour.”
(b) Wind shift.
Whenever a wind shift
occurs, “WSHFT” will be included in remarks
followed by the time the wind shift began, e.g.,
WSHFT 30 FROPA “Wind shift at three zero due to
frontal passage.”
6. Visibility.
Prevailing visibility is reported in
statute miles with “SM” appended to it.
EXAMPLE
−
7SM
− seven statute miles
15SM
− fifteen statute miles
1
/
2
SM
− one−half statute mile
(a) Tower/surface visibility.
If either visi-
bility (tower or surface) is below four statute miles,
the lesser of the two will be reported in the body of the
report; the greater will be reported in remarks.
(b) Automated visibility.
ASOS/AWSS
visibility stations will show visibility 10 or greater
than 10 miles as “10SM.” AWOS visibility stations
will show visibility less than
1
/
4
statute mile as
“M
1
/
4
SM” and visibility 10 or greater than 10 miles
as “10SM.”
NOTE
−
Automated sites that are augmented by human observer to
meet service level requirements can report 0, 1/16 SM, and
1/8 SM visibility increments.
(c) Variable visibility.
Variable visibility is
shown in remarks (when rapid increase or decrease
by
1
/
2
statute mile or more and the average prevailing
visibility is less than three miles) e.g., VIS 1V2
“visibility variable between one and two.”
(d) Sector visibility.
Sector visibility is
shown in remarks when it differs from the prevailing
visibility, and either the prevailing or sector visibility
is less than three miles.
EXAMPLE
−
VIS N2 − visibility north two
7. Runway Visual Range (When Reported).
“R” identifies the group followed by the runway
heading (and parallel runway designator, if needed)
“/” and the visual range in feet (meters in other
countries) followed with “FT” (feet is not spoken).
(a) Variability Values.
When RVR varies
(by more than on reportable value), the lowest and
highest values are shown with “V” between them.
(b) Maximum/Minimum Range.
“P” indi-
cates an observed RVR is above the maximum value
for this system (spoken as “more than”). “M”
indicates an observed RVR is below the minimum
value which can be determined by the system (spoken
as “less than”).
EXAMPLE
−
R32L/1200FT
− runway three two left R−V−R one thousand
two hundred.
R27R/M1000V4000FT
− runway two seven right R−V−R
variable from less than one thousand to four thousand.