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VVVV - Horizontal
Visibility (see: CAVOK,
RVR - Runway visual range)
measured in meters.
The following increments are used:
10m - below 100m
100m - below 1000m
500m - between 1000m and 5000m
1000m - between 5000m and 9000m
9999 - 10Km and above.
Some countries use statute mile(SM) as a unit
to measure visibility.
D - Direction
When the horizontal visibility is not the same in
all directions, a minimum
and maximum visibility may be given followed the
direction.
Values for D are:
N - North, NE - Northeast, E
- East, SE - Southeast, S -
South,
SW - Southwest, W - West, NW
- Northwest.
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NNNhhh - Clouds (see:
CAVOK, NSC,
Cloud
Type, Cloud
Atlas)
NNN - Cloud amount, shown by the following
abbreviations:
FEW
- 1 to 2 octas
SCT
- 3 to 4 octas
BKN
- 5 to 7 octas
OVC
- 8 octas
hhh - Cloud height in feet above station
level (or AGL).
VVhhh - Vertical
visibility
When the sky is obscured and instrumentation is
available to measure
vertical visibility, hhh is given in increments of
100ft.
TT/TdTd -
Temperatures
TT - Temperature, Td - Dewpoint
Temperature
Temperatures in South Africa are measured in
Celsius.
QPPPP - QNH
Q - indicator for QNH, PPPP - Pressure
value.
Measured in hecto Pascal (HPa), 1 Hpa = 1
mB(millibar)
REWW - Recent
Significant Weather (see: WW,
NSW)
TTTTT - Trend Forecast
This type of forecast is used to indicate
significant changes in the weather
expected within a two hour period from the time of
issue of the Metar.
RMK -
Remark
Used supply additional information that do fall
within the boundaries of
the general code. One such example is the tops of CB
that are visible
from the point of observation but the cloud may be
200Km away.
Eg. RMK CB DISTANT SW.
= -
Indicates the end of the report/bulletin
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CAVOK
Visibility greater than 10Km, no cloud below
5000 ft or minimum sector altitude, whichever is the
lowest and no CB or over development and no
significant weather.
NOSIG - No Significant Change
Nosig is added to the METARs of locations where no
forecaster is available
to give trend forecast. It is omitted with Auto
METARs and those from
smaller locations.
RD/VVVV - Runway
visual range
At aerodromes where instruments are used to measure
visibility this group
will be included in the METAR when significant.
RD/ - Runway designator/point where the
visibility is measured.
VVVV - Visibility.
RD/VVVVvVVVV -
This format is used when the visibility fluctuates
at a
runway point. The fluctuation is considered
significant when the visibility
during the last 5 seconds changes by 50m or 20% of
the mean visibility
of the previous 10 minutes.
v - tendency for
the visibility to change by 100m or more from the
mean,
terms used are: U -
upward, D - downward, N - no tendency.
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NSW - No significant
Weather (TAF only)
NSC - No Significant
Cloud.
NOBS - No Observation. Appears at the end
of a TAF when no surface observation is available
for the location at the time when the TAF is issued.
VRB - Variable
Used when windspeed is less than 3KT or during a
violent thunderstorm
when wind direction can not be determined.
Cloud Type
Abbreviations for cloud used in METAR,
TAF and Sigwx Charts.
CB - Cumulonimbus
TCU - Towering Cumulus
Abbreviations used only in Sigwx
Charts.
ST - Stratus
SC - Stratocumulus
CU - Cumulus
NS - Nimbo Stratus
AC - Alto Cumulus
AS - Alto Stratus
The following cloud types are not considered to
be significant to aviation
and therefore not in any aviation forecasts:
Ci - Cirrus
Cs - Cirrostratus
Cc - Cirrocumulus
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DDFMTL - Period of
validity
DD - Day, FM - Hour, start of the period, TL - Hour,
end of period
Eg 120312 - Taf is valid for the 12th day of the
month, from 03:00z until 12:00z.
Two sets of TAFs are issued in South Africa:
FC-TAF: TAF valid for 6 to 9 hours, updated in 3
hour intervals.
FT-TAF: Valid for 18 to 24 hours, updated at 6 hour
intervals.
Note: Not all locations have FT-TAFs.
TXTtTt/HHZTNTtTt/HHZ -
Forecast Max and Min temperature
TX - Indicator for Maximum temperature
TtTt - Temperature value in Celsius
TN - Indicator for Minimum temperature
HH - Forecast hour, i.e. the time(hour) when
the temperature is expected
Z - Time Zone indicator, Z=GMT.
{ BECMG HHHH / FMHHmm / TEMPO HHHH
(TLHHmm)}
{PROB % HHHH}
HHHH - Period of validity
HH on the left is the hour indicating the start of
time while HH on the
right will be the end of the period.
Eg. 1317 - a change from 13:00Z to 17:00Z.
BECMG - Becoming
Used to indicate a gradual change in some of the
forecast elements.
TAF - BECMG is always followed by a time group(HHHH)
and does not exceed 4 hours.
TREND(METAR) - This forecast is only 2 hours and
need not be followed by a time.
FMHHmm - From
HH - Hour, mm - minute from when the change
is expected.
TAF - Used when a significant change in all elements
is expected at a specific time.
TREND(METAR) - Used with BECMG and may be used to
indicate a change in
some or all the elements, e.g. BECMG FM2015.
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TEMPO - Temporary
fluctuation in some of the elements lasting for
periods of
30 minutes or more but not longer than one hour with
each instance and does
not cover more than half of the total period
indicated by HHHH.
TLHHmm - Until
(used in METAR only)
HH - Hour, mm - minute until
when the change is expected to stop.
TL may be used with FM.
PROB % - Probability
% - percentage, only 30 or 40 is used. If a
higher probability is expected
TEMPO is used.
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SPECI - Special METAR
A SPECI is the same as a METAR but issued when the
following criteria is met:
1. Mean surface wind direction has changed by 30
degrees or more, the mean
wind speed before and/or after
the change being 20Kt or more.
2. Mean surface wind speed has change by 10Kt or
more, the wind speed
before and/or after the change be
30Kt or more.
3. Wind Gusts have increased by 10Kt or more, the
mean wind speed before
and/or after the change being
15Kt or more.
4. Visibility changes to or pass:
a. 1500 or 3000m (SPECI) - 150,
350, 600, 800,1500, 3000m (TAF)
b. 5000m where significant
numbers of VFR flights are operating.
5. Runway visual range changes to or pass 150, 350,
600, 800m.
6. When any combination of weather in the
significant weather
table begins,
ends or changes intensity.
7. Height of the base of the lowest cloud layer of
BKN or OVC extent,
changes to or passes:
a. 100, 200, 500 or 1000ft.
b. 1500ft where significant
numbers of VFR flights are operating.
8. When the amount of cloud below 1500ft changes
from:
a. SKC, FEW, SCT to BKN or OVC
b. BKN or OVC to SKC, FEW, SCT
9. When the sky is obscured and vertical visibility
changes to or pass
100, 200, 500, 1000ft.
10. Increase in temperature of 2 degrees Celsius or
more.
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