Page 150 - UK ATM ANS Regulations (Consolidated) 201121

Part MET - ANNEX V - Specific Requirements for the Providers of Meteorological
Services

and upper-air temperature shall be issued for points separated by no more than 300 NM
and for, as a minimum, the following altitudes: 2 000, 5 000 and 10 000 ft (600, 1 500 and
3 000 m) and 15 000 ft (4 500 m) in mountainous areas. The issuance of forecasts of
upper wind and upper- air temperature at an altitude of 2 000 ft (600 m) may be subject to
local orographic considerations as determined by the competent authority.
(b) When chart form is used for area forecasts for low-level flights, the forecast of SIGWX
phenomena shall be issued as low-level SIGWX forecast for flight levels up to 100, or up
to flight level 150 in mountainous areas, or higher, where necessary. Low-level SIGWX
forecasts shall include:
(1) the following phenomena warranting the issuance of a SIGMET: icing, turbulence,
cumulonimbus clouds that are obscured, frequent, embedded or occurring at a
squall line, sandstorms/dust storms and volcanic eruptions or a release of
radioactive materials into the atmosphere, and which are expected to affect low-
level flights;
(2) the following elements in area forecasts for low-level flights: surface wind, surface
visibility, significant weather phenomena, mountain obscuration, cloud, icing,
turbulence, mountain wave and height of zero-degree isotherm.
(c) When the competent authority has determined that the density of traffic operating below
flight level 100 warrants the issuance of an AIRMET, the area forecasts shall be issued to
cover the layer between the ground and flight level 100, or up to flight level 150 in
mountainous areas, or higher, where necessary, and shall contain information on en-route
weather phenomena hazardous to low-level flights, in support of the issuance of the
AIRMET and the additional information required for low-level flights.
MET.TR.260 AMC1 Area forecasts for low-level flights
AMENDMENT OF LOW-LEVEL FORECASTS
(a) In case the AIRMET/low-level forecast concept is not fully implemented, the criteria for
amendments should as a minimum include the weather phenomena hazardous to low-
level flights, which constitute the criteria for the issuance of AIRMET.
(b) When low-level forecast is issued as a SIGWX chart or as a wind and temperature (W+T)
chart, it should, as appropriate, include the cloud/visibility information in the form of
visibility/cloud base category which should be provided for well-defined sub-areas and/or
route segments. For each sub-area and/or route segment, the reference height to which
the cloud base information refers should be specified.
(c) The graphical part of a SIGWX chart should depict the weather situation at the beginning
of the validity period. Significant changes of initial weather parameters should be depicted
together with time intervals determining the duration of expected changes.
MET.TR.265 Volcanic ash advisory centre responsibilities
(a) The advisory information on volcanic ash shall be issued in abbreviated plain language
and in accordance with the template shown in Appendix 6. When no abbreviations are
available, English plain language text, to be kept to a minimum, shall be used.
(b) Volcanic ash advisory, if disseminated in digital form, shall be:
(1) formatted in accordance with a globally interoperable information exchange model
and shall use geography markup language (GML);
(2) accompanied by the appropriate metadata.
(c) Volcanic ash advisory information, when prepared in graphical format, shall be issued
using the portable network graphics (PNG) format.
MET.TR.265(a) GM1 Volcanic ash advisory centres (VAACs) responsibilities

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