1 — INTRODUCTION
The Royal Netherlands Meteorological Institute (KNMI) is responsible
for all civil aeronautical meteorological information in the Netherlands.
This document is intended to inform aeronautical users about the
characteristics of automated aeronautical MET observations and where they
are available. The MET observations are disseminated:
- locally via ATIS as local MET reports and local special MET
reports;
- (inter)nationally in the AUTO METAR format; and
- through ATC via their respective frequencies.
1.1 GRONINGEN/Eelde and MAASTRICHT/Maastricht Aachen
For the aerodromes GRONINGEN/Eelde and MAASTRICHT/Maastricht Aachen,
aeronautical MET observation reports are produced without a local observer
(H24). Continuous monitoring is provided by the central forecast office of
KNMI in De Bilt.
1.2 ROTTERDAM/Rotterdam
As of 15 March 2011 the aeronautical MET observation reports for the
aerodrome ROTTERDAM/Rotterdam are produced without a local observer (H24).
Continuous monitoring is provided by the central forecast office of KNMI
in De Bilt.
2 — CHARACTERISTICS OF AUTOMATED REPORTS
2.1 Information in manually compiled and automated MET observation
reports
The following values are measured automatically and reported
identically in reports compiled by a human observer and in
automated reports:
- Wind
- RVR
- Air temperature
- Dew point
- QNH.
Meteorologists of the central forecast office in De Bilt shall, when
appropriate, add the following items to the automated reports:
- RSM: runway state message
- LLTI: low level temperature inversion
- Windshear report
- Windshear forecast
- TREND: a two hour forecast at the end of the observation
report.
2.2 Differences between manual and automated MET observation
reports
2.2.1 Visibility
- Reported visibility in AUTO METAR may occasionally vary
compared to a manual observation in situations where visibility is
rather inhomogeneous. This is due to the point measurement principle
in AUTO METAR. For example, when fog is reported in AUTO METAR and
no fog is present above the runway, visibility at the runway may be
higher.
2.2.2 Clouds
- Cloud base height reports in automated reports are based on
observations by laser ceilometers. Cloud cover (cloud amount) is
derived by using a specific algorithm to cater for the fact that a
ceilometer provides point measurements.
- Cloud type in the form of cumulonimbus (CB) or towering
cumulus (TCU) will be included in automated reports based on an
algorithm which uses weather radar-reflectivity and satellite
data.
- Additional information about the convective characteristics of
the clouds through (near) real time weather radar observations is
available via MWO De Bilt, Meteorological Self Briefing units, ATC
centres and via KNMI's aviation weather website www.aviationweather.nl.
2.3 Information not provided in automated MET observation
reports
Automated MET observation reports are part of the meteorological
service provision comprising of observations, forecasts, warnings and
advices. If the automated MET observations are not fully able to
determine all weather phenomena and descriptors, the meteorologists
located in De Bilt are available for briefing or consultation. Also,
additional information is available at KNMI's aviation weather website
www.aviationweather.nl.
2.3.1 Present weather
Automated MET reports contain a subset of present weather codes,
not the complete set of METAR and local and special MET reports.
- Present weather in the vicinity of the aerodrome cannot be
observed and therefore the code VC is not used in automated
reports.
- If precipitation type can not be detected, the code UP
(unknown precipitation) is reported.
- The following weather phenomena or descriptors are not
reported: FC, SS, DS, PO, SA, DU, FU, VA, MI, BC, PR, DR and
BL.
- Observations of present weather are carried out by a present
weather sensor located on a fixed location. Only weather occurring
at that specific location will be reported.
- Thunderstorms (TS) are reported when lightning is detected
within a distance of 15 km from the aerodrome reference point (ARP)
based on information gathered by the national lightning detection
network.
3 — CODING PRACTISES IN AUTOMATED REPORTS
3.1 Codes not provided in automated observation reports
- FC, SS, DS, PO, SA, DU, FU, VA, MI, BC, PR, DR and BL.
- VC: vicinity.
- CAVOK: clouds and visibility OK.
- SKC: the term "sky clear" is no longer used in manual and
automated MET observations.
3.2 Codes used in automated observation reports only
- AUTO: indicating an automated report.
- NCD: no clouds detected. When the sensor does not detect clouds
and no CB/TCU are detected, the code NCD is reported due to the point
measurement principle.
- UP: unknown precipitation. Not all types of precipitation are
recognised by the present weather sensor, see paragraph 2.3.
3.3 Codes used in manual and automated MET observation
reports
- NSC: no significant clouds. When no clouds of operational
significance (cloud base 5000 ft or more and no CB/TCU) are observed,
the abbreviation "NSC" is used.
3.4 Additional remarks in the REMARK section
AUTO METAR can contain up to three remarks in the REMARK section.
The REMARK section is disseminated in the Netherlands only, in line with
international data exchange rules.
- RMK TS INFO NOT AVBL: in situations where lightning data is not
available.
- RMK CB INFO NOT AVBL: in situations where radar reflectivity
data is not available.
- RMK WX INFO NOT AVBL: in situations where the local present
weather sensor data is not available.
It is essential that the absence of weather or cloud information in
an automated report is clearly identified as caused by the absence of the
phenomena itself, or due to failure of the sensor. When cloud height
sensor information is not available due to technical reasons, this will be
reported in the cloud group using six slashes: "//////".