TAF Amendment Watch

Select a station to begin

Pulls the latest TAF and the last three hours of METAR/SPECI from aviationweather.gov, then checks wind, thunderstorm, altimeter, TEMPO and change-group rules and any ceiling/visibility category change.

Category criteria

Lowest landing min ceiling (ft)Lowest landing min vis (m)

OCONUS host-nation values (5000/3000 m)

Cat	Ceiling ≥	Vis ≥
E	2,000 ft	4800 m (3)
D	1,000 ft	3200 m (2)
C	700 ft	3200 m (2)
B	200 ft	800 m (1/2)
A	below	below

How the check works

The newest observation is compared with the prevailing TAF conditions at that time (initial, FM and BECMG groups). Active TEMPO/PROB groups and BECMG transitions are accepted alternatives.

Category change between forecast and observation → amend.
Wind speed or gusts off by ≥10 kt, or direction off by >30° when forecast winds are ≥15 kt → amend.
Altimeter crossing 31.00 or 28.00 INS not forecast → amend.
Thunderstorm start or end not forecast → amend.
TEMPO conditions persisting ≥30 min (45 for TS) or not occurring within the first hour → amend.
FM/BECMG changes get a 30-minute window before an amendment is required.

Icing, turbulence, warning/advisory and representativeness rules need forecaster judgment and are flagged for review.

Questions or suggestions?

If there are any issues or suggestions, please email TSgt Jasmine Prisbe at jasmine.prisbe@us.af.mil.