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Above that, it is indicated as P6SM.
Thus, obstructions to vision are only
mentioned under 6 miles. A dashed
line as a border indicates intermittent
or showery precip. A solid line
means continuous.
Winds
Sustained windspeeds over 20 kts are
shown with wind barbs. A G means
gusts, with the peak value in knots:
Icing & Turbulence
Icing is shown for moderate and
severe levels, with bases and tops, in
the same way cloud is shown, but
with a different symbol (left, below):
The symbol for turbulence is the one
on the right, above.
Weather 107
Weather Information
FDAs
Forecasts for Upper Level Winds and
Temperatures, prepared twice daily for
various altitudes, as tabulated figures:
3000 6000 9000
YVR 9900 2415-07 2430-10
YYF 2523 2432-04 2338-08
You have to interpolate for the
height you will be at which, in the
exam, will be nowhere near any of
the lines in the table - for example, at
7,500 feet, the figures would be
something like 2422-8.
A minus sign means temperatures
below 0°C. Wind velocity is in
degrees true and knots, 9900 means
light and variable and high winds are
above 18,000 feet.
TAFs
Aerodrome Weather Forecasts describe
the most probable forecast
conditions within 5 nm of the runway
centres for 12 or 24 hours after the
valid time, which may be 05, 11, 17
and 23Z. A TAF may be sub-divided
into self-contained parts by the
abbreviation ‘FM’ (from) followed
by the time UTC to the nearest hour,
expressed as 2 figures (e.g. FM09).
Abbreviations used are above. Note,
however, that the term CAVOK
(Ceiling and Visibility OK) is not used
in TAFs Canada, and RMK is not
used elsewhere.
Station Identifier
4-letter ICAO indicator for
aerodrome.
Message Type
TAF or TAF AMD, for amended.
Date and Time of Issue
A 6-digit code, with the date as the
first two, then the time in UTC.
Validity Period
The start and finish times in whole
hours UTC, e.g. 0716 (0700 to 1600
hrs UTC). This is normally 12, but
may be 24, or otherwise if amended.
Winds
To the nearest 10°, in knots.
000000KT is calm, VRB means
variable, less than 3 kts. Gusts are
given in 2 digits. WS means
windshear, when significant, with
speed and direction at a height.
Visibility
In statute miles below 6. P6SM
means greater the 6 statute miles.
Weather
A minus (-) means light, no sign is
moderate, and + means heavy. It is
described in 7 ways, such as SH for
showers, DR for drifting, FZ for
freezing, MI for shallow, BL for
blowing and BC for batches.
FC=Funnel Cloud (Tornado),
TS=Thunderstorm, DZ=Drizzle,
FG=Fog (< 1 km), BR=Mist (> 1
km), GS=Small Hail, FU=Smoke,
SS=Sandstorm, VA=Volcanic Ash,
PO=Dust/Sand, RA=Rain,
SG=Snow Grains, PL=Ice Pellets,
IC=Ice Crystals, SA=Sand,
SN=Snow, HZ=Haze, GR=Hail,
DU=Dust, SQ=Squall,
DS=Duststorm.
Cloud
Up to 4 cloud groups, in ascending
order of bases, and cumulative, based
on the amount of the sky covered, in
eighths, or oktas. The cloud ceiling is the
108 Canadian Private Pilot Studies
height of the first layer that is broken
or overcast. The first group is the
lowest individual layer; the second
the next of more than 2 oktas and
the third the next higher of more
than 4 oktas. A group has 3 letters
for the amount (FEW = 1 to 2
oktas, SCT, or scattered = 3 to 4
oktas; BKN, or broken, = 5 to 7
oktas, and OVC, or overcast = 8
oktas) and 3 for the height of the
cloud base in hundreds of feet above
aerodrome level. For clear sky, this
will be SKC. VV means the vertical
visibility in hundreds of feet which, if
you get it at all, means you have an
obscured ceiling. CB means
thunderstorms and is added as
necessary.
Significant Changes
In addition to FM and the time (see
above) significant changes may be
indicated by BECMG (becoming)
which is followed by a four-figure
group showing the beginning and
ending of the period when change is
expected. The change is expected to
be permanent, and to occur at an
unspecified time within it. TEMPO
(temporarily) will similarly be
followed by a 4-figure time group,
indicating temporary fluctuations in
forecast conditions which may last
less than 1 hour or less than half the
period indicated in total. PROB
(probability) signifies a significant
change, 30 or 40%, followed by a
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