Change qualifier of a trend-type forecast or an aerodrome forecast.<br /></p><p><br /></p><p>Defined in WMO No. 306 Vol I.1; FM-15 METAR, FM-16 SPECI and FM-51 TAF.<br /></p><p>See also BUFR Code-table 0 08 016.<br /></p><p><br /></p><p>Conditions typically reported as NO_SIGNFICANT_CHANGE (NSC) shall be encoded using the "nothingOfOperationalSignificance" nil-reason code.<br /></p><p><br /></p><p>[<font color="#ff0000">http://data.wmo.int/def/nil-reason/nothingOfOperationalSignificance</font>]<br /></p>
When the change is forecast to commence at the beginning of the forecast period and be completed by the end of that period, or when the change is forecast to occur within the forecast period but the time of the change is uncertain (possibly shortly after the beginning of the forecast period, or midway or near the end of that period), the change shall be indicated by only the change indicator BECMG.
The change indicator TEMPO shall be used to describe expected temporary fluctuations to meteorological conditions which reach or pass specified threshold criteria and last for a period of less than one hour in each instance and in the aggregate cover less than half of the forecast period during which the fluctuations are expected to occur.