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,[1] and is based on an actual weather report, such as a METAR or SPECI and appended to the end of it.
[1] 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.
[citation needed] In this example the METAR indicates it is from EGXE (RAF Leeming) at 1150 UTC on Day 6.
Temporary deterioration to 6 km visibility in a moderate rain shower with scattered at 2000 ft, colour state White.