JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
Forecast Times
The 6-digit number following the message heading indicates the forecast period of the entire
TAF, which is usually 24 hours (Figure 6-17). The first two digits represent the date of the
forecast. The second two digits indicate the beginning hour of the forecast, and the final two
digits indicate the ending hour of the forecast. For example, 260909 means that the forecast
begins at 0900Z on the 26 th day of the month and covers the 24-hour period up to but not
including 0900Z the next day. U.S. civil stations include date and time of transmission prior to
the forecast period (i.e., 091720Z 091818).
KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS
Figure 6-17 — TAF Time Group
Whenever the forecast is an AMD, COR, or RTD, the times may not be for a 24-hour period and
will be indicated accordingly. When USN/USMC stations amend, correct, or have a routine
delayed forecast, a remark will be appended to the last line of the forecast with the appropriate
time (e.g., AMD2218).
Winds
Wind direction is forecasted to the nearest 10 degrees true, in the direction from which the wind
will be blowing (Figure 6-18). If wind direction is expected to vary by 60 degrees or more, the
limits of variability will be noted as a remark, e.g., WND 270V350. The contraction VRB can
only be used to replace direction when forecasted wind speed is 6 knots or less, or in more rare
cases when it is impossible to forecast a single wind direction, such as for thunderstorms.
KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS
Figure 6-18 — TAF Winds
Forecasted wind speeds and gust data are given in whole knots; if the wind speed is over 100
knots, then 3 digits are used. Calm winds are represented by “00000” for the wind group. “G”
will be included to indicate gusts when the peak wind exceeds the average wind by 10 knots or
more. Presently all U.S. winds are in knots and the contraction KT will end these wind groups.
Some overseas stations use KPH (kilometers per hour) or MPS (meters per second).
Visibility, Weather, and Obstructions to Vision
For TAFs, forecasted prevailing visibility is reported in meters and rounded down to the nearest
reportable value (Figure 6-19). U.S. civil stations, however, will report visibility in
KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS
Figure 6-19 — TAF Visibility Group
statute miles (Table 6-5). Whenever the prevailing visibility is forecasted to be 9000 meters or
less (6 miles or less) the weather or obstructions to vision causing the reduced visibility will be
included using the same notation as the METAR present weather group, described above in
Table 6-2. A visibility code of “9999” indicates 7 miles visibility or greater is forecast, i.e.
unlimited visibility. When appropriate, RVRs will follow immediately after the prevailing
visibility.
6-16 Version 3.2/Dec 08