AMC1 MET.TR.220(f) Aerodrome forecasts

• ED Decision 2017/001/R found in: ATM/ANS Provision of Services (2017/373) (Mar 2025)

AMC1 MET.TR.220(f) Aerodrome forecasts ED Decision 2017/001/R TAF — USE OF CHANGE GROUPS The criteria used for the inclusion of change groups in TAF or amendments to TAF should be based on the following: (a) when the mean surface wind direction is forecasted to change by 60° or more, the mean speed before and/or after the change being 10 kt (5 m/s) or more; (b) when the mean surface wind speed is forecasted to change by 10 kt (5 m/s) or more; (c) when the variation from the mean surface wind speed (gusts) is forecasted to change by 10 kt (5 m/s) or more, the mean speed before and/or after the change being 15 kt (7.5 m/s) or more; (d) when the surface wind is forecasted to change through values of operational significance; (e) when the visibility is forecasted to improve and change to or pass through one or more of the following values, or when the visibility is forecasted to deteriorate and pass through one or more of the following values: (1) 150, 350, 600, 800, 1 500 or 3 000 m; and (2) 5 000 m in cases where significant numbers of flights are operated in accordance with the visual flight rules; (f) when any of the following weather phenomena, or combinations thereof, are forecasted to begin or end: (1) low drifting dust, sand or snow; (2) blowing dust, sand or snow; (3) squall; and (4) funnel cloud (tornado or waterspout); (g) when the height of base of the lowest layer or mass of cloud of BKN or OVC extent is forecasted to lift and change to or pass through one or more of the following values, or when the height of the lowest layer or mass of cloud of BKN or OVC extent is forecasted to lower and pass through one or more of the following values: (1) 100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m); or (2) 1 500 ft (450 m) in cases where significant numbers of flights are operated in accordance with the visual flight rules; (h) when the amount of a layer or mass of cloud below 1 500 ft (450 m) is forecasted to change: (1) from NSC, FEW or SCT to BKN or OVC; or (2) from BKN or OVC to NSC, FEW or SCT; (i) when the vertical visibility is forecasted to improve and change to or pass through one or more of the following values, or when the vertical visibility is forecasted to deteriorate and pass through one or more of the following values: 100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m); and (j) any other criteria based on local aerodrome operating minima, as agreed between the aerodrome meteorological office and the operators. AMC1 MET.TR.220(f) Aerodrome forecasts ED Decision 2017/001/R TAF — USE OF CHANGE GROUPS The criteria used for the inclusion of change groups in TAF or amendments to TAF should be based on the following: (a)       when the mean surface wind direction is forecasted to change by 60° or more, the mean speed before and/or after the change being 10 kt (5 m/s) or more; (b)       when the mean surface wind speed is forecasted to change by 10 kt (5 m/s) or more; (c)       when the variation from the mean surface wind speed (gusts) is forecasted to change by 10 kt (5 m/s) or more, the mean speed before and/or after the change being 15 kt (7.5 m/s) or more; (d)       when the surface wind is forecasted to change through values of operational significance; (e)       when the visibility is forecasted to improve and change to or pass through one or more of the following values, or when the visibility is forecasted to deteriorate and pass through one or more of the following values: (1)       150, 350, 600, 800, 1 500 or 3 000 m; and (2)       5 000 m in cases where significant numbers of flights are operated in accordance with the visual flight rules; (f)        when any of the following weather phenomena, or combinations thereof, are forecasted to begin or end: (1)       low drifting dust, sand or snow; (2)       blowing dust, sand or snow; (3)       squall; and (4)       funnel cloud (tornado or waterspout); (g)       when the height of base of the lowest layer or mass of cloud of BKN or OVC extent is forecasted to lift and change to or pass through one or more of the following values, or when the height of the lowest layer or mass of cloud of BKN or OVC extent is forecasted to lower and pass through one or more of the following values: (1)       100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m); or (2)       1 500 ft (450 m) in cases where significant numbers of flights are operated in accordance with the visual flight rules; (h)       when the amount of a layer or mass of cloud below 1 500 ft (450 m) is forecasted to change: (1)       from NSC, FEW or SCT to BKN or OVC; or (2)       from BKN or OVC to NSC, FEW or SCT; (i)        when the vertical visibility is forecasted to improve and change to or pass through one or more of the following values, or when the vertical visibility is forecasted to deteriorate and pass through one or more of the following values: 100, 200, 500 or 1 000 ft (30, 60, 150 or 300 m); and (j)        any other criteria based on local aerodrome operating minima, as agreed between the aerodrome meteorological office and the operators.