All amended forecasts will use the time the forecast
is amended as the beginning time, and the standard time
of the forecast period as the ending time. For example,
if the 281515 TAF is amended at 281700, it would be
encoded 281715. The abbreviation "AMD" is used to
indicate an amended TAF. The abbreviation "RTD"
indicates a routine delay, and "COR" indicates a
corrected TAF. Specific meteorological elements of the
TAF code are as follows:
1. Element dddffGfmfmKT is the surface wind
direction to the nearest 10 degrees, and the wind speed
in knots. Gusts are also included when applicable. The
contraction "VRB" may be used for direction when the
average wind speed is 6 knots or less. Calm winds are
encoded as "00000KT."
2. Element VVVV is the prevailing visibility in
meters, rounded down to the nearest reportable value.
Reportable values are identical with those in NAV-
METOCCOMINST 3141.2, Surface METAR Observa-
tions User’s Manual. Weather and/or obstructions to
vision must be included whenever the prevailing
visibility is forecast to be 9000 meters (6 SM) or less.
3. Element w'w' includes the forecast weather
and obstructions to vision using the standard
abbreviations as outlined in NAVMETOCCOMINST
3141.2 and NAVMETOCCOMINST 3144.1, United
States Navy Manual for Ship’s Surface Weather
Observations.
4. Element NsNsNshshshs is the sky cover group
using standard abbreviations (i.e., SCT, FEW, etc.).
Heights are reported in hundreds of feet AGL in
accordance with NAVMETOCCOMINST 3141.2 and
NAVMETOCCOMINST 3144.1. This group is
reported as often as necessary to indicateall forecast sky
cover layers up to the forecast overcast (8/8) layer. The
summation principle used in the METAR code also
applies to the TAF code. Groups are reported in
ascending order. Clear skies are reported as "SKC."
Types of clouds are not encoded with the exception of
cumulonimbus clouds. which are always reported as a
separate group using the abbreviation CB. For
example, 3/8 cumulonimbus clouds at 2,500 feet would
be encoded as SCT025CB.
Partial obscurations are considered as the first layer
in the sky cover group (i.e., fog forecast to cover 2/8 of
the station would be encoded as SCT000). Total
obscurations are reported using the VVhshshs group as
p e r N A V M E T O C C O M I N S T 3 1 4 1 . 2 a n d
NAVMETOCCOMINST 3144.1.
5. The element WShwshwshws/dddffKT or
WSCONDS is the non-convective, low-level wind
shear (LLWS) group. This group is used only to
forecast wind shear not associated with convective
activity from the surface to 2,000 feet. The abbreviation
WS is the LLWS indicator, and hwshwshws is the
forecast height of the wind shear in hundreds of feet
AGL. The contraction WSCONDS indicates that wind
shear conditions are present but complete information
cannot be reliably forecast.
6. The element 6IchihihitL is the icing group (not
associated with thunderstorms). The number 6 is the
icing indicator and Ic represents the type of icing, as
encoded from table 3-2. The hihihi is the icing layer
base in hundreds of feet AGL. The tL represents the
thickness of the icing layer in thousands of feet, as
encoded from table 3-3. Example: 650203 indicates
moderate icing in cloud from 2,000 to 5,000 feet.
7. Element 5BhbhbhbtL is the turbulence group
(not associated with thunderstorms). The number 5 is
the turbulence indicator and the letter "B" is the
turbulence type and intensity encoded from table 3-4.
Extreme turbulence is encoded with an "X." The
hbhbhb is the forecast height of the turbulence in
hundreds of feet AGL. The tL is the thickness of the
turbulence layer in thousands of feet AGL, as encoded
from table 3-3. Example: 561205 indicates occasional
severe turbulence in clear air from 12,000 to 17,000
feet.
Table 3-2.—Icing Type (Ic)
Ic =
Type of forecast ice accretion on external
parts of aircraft
Code
Figure
0
No Icing
1
Light Icing
2
Light Icing in Cloud
3
Light Icing in Precipitation
4
Moderate Icing
5
Moderate Icing in Cloud
6
Moderate Icing in Precipitation
7
Severe Icing
8
Severe Icing in Cloud
9 Severe Icing in Precipitation
3-2
