JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
For example, in Figure 6-24, the temporary occurrence of thunderstorms and rain showers are
forecast to exist only from 1900 up to, but not including, 0200. After this time, the conditions
listed in the TEMPO line will be replaced by the forecast from other lines.
PROB Group
KNSE TAF 260909 28004KT 9000 HZ SCT020 SCT200 QNH2998INS
FM1200 26007KT 9000 HZ SCT025 SCT080 BKN250 QNH2996INS
VCSHRA
BECMG 1416 9999 SCT025CB SCT250
BECMG 1718 23015G25KT 530004
TEMPO 1902 8000 TSSHRA SCT010 BKN025CB
FM0200 27010KT 9999 SCT030 BKN080 BKN250 QNH3001INS 20/09Z
Figure 6-24 — TAF TEMPO Group
Civilian stations will sometimes forecast the probability of occurrence of thunderstorms or other
precipitation events. Such a line begins with “PROB,” followed by a 2-digit percentage and the
corresponding weather, as this example illustrates:
PROB40 1/2SM +TSRA OVC005CB
This station forecasts a 40% chance of heavy rain from thunderstorms, producing an overcast
ceiling of cumulonimbus clouds at 500 feet, with visibility ½ mile. This group may also be
followed by a 4-digit time period group giving the beginning and ending time for the occurrence.
USN/USMC stations will not use this change group.
Change Groups and Times (FROM/TO)
In order to use a TAF effectively, one must know how long a given pattern of weather will last,
as well as what that pattern will be. To do this, establish the FROM and TO times of that pattern.
(Note: in this text, TO will mean up TO, but not including that time.)
• The times on the first line of code, after the location, are the FROM and TO date and
times for the entire forecast, and the beginning (FROM) time of the first forecast line.
• The time listed immediately after a FM can be a beginning time of a new pattern of
weather as well as a TO time of a previously defined pattern, depending upon where it
falls in the forecast.
• The first two digits of the 4-digit time group following BECMG will be the beginning
(FROM) time of the new forecast elements, and the last two digits are the ending (TO)
time of the previous pattern.
• The first two digits of the 4-digit time group shown after a TEMPO are the beginning
(FROM) time, and the last two digits are the ending (TO) time for that TAF line.
6-22 Version 3.2/Dec 08