6.2 Introduction
We need to keep our aviation forecasts up-to-date with the best information that we have to best serve the needs of the people who rely on our products to make key decisions. There will be occasions when weather conditions change earlier or later than anticipated and our forecasts need to be amended.
The decision to amend relies on your judgment and assessment of the meteorological conditions and expectations. A minor fluctuation in the observation which is not expected to continue should not result in amending the TAF.
TAFs should be amended when:
- Conditions meeting amendment criteria are imminent or have occurred and those conditions are expected to persist (generally 30 minutes or longer).
or
- New guidance or information that indicates future conditions are expected to be in a different flight category rules (IFR, VFR) or meteorological thresholds which may impact customers.
Examples for when TAFs should be amended:
- Conditions described by "TEMPO" which become prevailing.
- TAF forecast indicates IFR conditions, but VFR conditions are occurring and expected to persist.
- Low airport criteria (not specifically mentioned in the national criteria) that can impact local air traffic such as wind direction.
- Conditions described by "PROB30"or "TEMPO"which are no longer expected.
Amendments should always be issued as rapidly and accurately as possible in response to the needs of the aviation community. However, amendments may not always be justified for events that are expected to be brief in duration. You should try to avoid "chasing the observations".