In aviation meteorology, a trend type forecast (TTF), also known simply as a trend, is a weather forecast written by a person on location at a major airport or military base. A TTF is a professionally considered forecast for weather over a two-hour period, and is based on an actual weather report, such as a METAR or SPECI and appended to the end of it. A TTF is similar to or sometimes in addition to a TAF, a terminal aerodrome forecast, but during the TTF's validity period is considered superior to a TAF.
EGXE 061150Z 03010KT 9999 FEW020 17/11 Q1014 BLU TEMPO 6000 SHRA SCT020 WHT=
The Trend reads TEMPO 6000 SHRA SCT020 WHT i.e. Temporary deterioration to 6 km visibility in a moderate rain shower with scattered at 2000 ft, colour state White.
- "Annex 3 to the Convention on International Civil Aviation – Meteorological Service for International Air Navigation", Sixteenth Edition July 2007, para 6.3.3, p. 6-2.