1.1 KNMI Aviation Services

The Royal Netherlands Meteorological Institute (KNMI) is designated as the meteorological authority for the provision of meteorological service for (international) air navigation in the Netherlands.

KNMI Aviation Services is the subdivision of the Institute charged with the provision of meteorological information.

1.2 Applicable ICAO documents

The international Standards, Recommended Practices and Procedures contained in the following ICAO documents are applicable:

Differences to these provisions are detailed in GEN 1.7.

3.1 Observing systems and operating procedures

Surface wind speed is measured by cup anemometers and wind direction by wind vanes at 33 FT/10 M above ground.
The unit knot (KT) is used to indicate surface wind speeds.

Reported visibility is lowest visibility. In METAR, TREND and TAF prevailing visibility is also available.

Runway visual range (RVR) assessments are made by using forward-scatter meters. Forward-scatter meters measure the back scatter of the atmosphere in terms of a back scatter factor for a distinct volume of air. The back scatter factor is converted to runway visual range taking into account background luminance and intensity of runway lights. The forward-scatter meters are calibrated using a standard transmissometer set. The background luminance is determined by measurements; the intensity setting of the runway lights is assumed to be 100 percent.

The reporting scale consists of increments of 25 M for RVR up to 400 M, increments of 50 M for RVR from 400 M up to 800 M and increments of 100 M for RVR above 800 M. For all main landing runways at AMSTERDAM/Schiphol, RVR readings from three locations along the runway are available. For each landing (take-off) runway the RVR values are designated A, B and C in accordance with the direction of landing (take-off). RVR values are provided in alphabetical order; A for touchdown and take-off area (TDZ), B for the midpoint (MID) and C for the stop-end or lift-off area of the runway (END). For RWY 18R, the A reflects the TDZ reading, the B reflects the MID and C reflects the END area of the runway. TDZ east and TDZ west will be compared and the lowest value shall be the TDZ reading, MID 1 and MID 2 will be compared and the lowest value shall be the MID reading.

Remote reading thermometers (thermistors) are used to measure the air temperature at 5 FT/1.50 M above the ground. Height of cloud base and cloud cover are obtained by measurement (ceilometers) and at AMSTERDAM/Schiphol also by visual estimation. The instruments are located in such way as to obtain observations that are representative for the take-off and landing areas (see paragraph 3).

4.1 Information for pre-flight planning

4.2 Meteorological information for general aviation

4.2.4 GA forecast: North Sea Area Forecast (NAF)

A NAF contains a forecast of the predominant weather in a specific area over the North Sea. The NAF area in the forecast is identified by the ICAO 4-letter location indicator of the offshore platform on which the automatic weather station is installed. Location indicator NAF area Platform EHAK 1 A12-CPP EHFD 2 F3-FB-1 EHDV 3 D15-FA-1 - 4 - EHHW 5 BG-OHVS2 EHKV 6 K14-FA-1C EHMG 7 L9-FF-1 EHMA 8 AWG-1 EHQN 9 HKN EHPG 10 P11-B NAFs are published daily 0600-2000 (0500-1900) UTC, for the 10 NAF areas. The number of NAFs can differ during the forecast period, based on the available observations. NAFs are valid for a 9-hour period and are scheduled every three hours. A NAF has the same layout out as a TAF, but has an additional remark field (RMK) that can be used to describe local weather in the NAF area in abbreviated plain language. The NAF contains more detailed information than the graphical low-level forecast (GLLFC).

8.1 General

The issuance of meteorological warnings such as SIGMET or AIRMET within the Amsterdam FIR is provided H24 by MWO De Bilt (EHDB).

8.2 SIGMET

A meteorological warning (SIGMET) will be issued by MWO De Bilt when the following weather phenomena are occurring, or expected to occur, in the Amsterdam FIR:

• obscured or embedded thunderstorms (with or without heavy hail)
• frequent thunderstorms (with or without heavy hail)
• thunderstorms in squall line (with or without heavy hail)
• severe turbulence
• severe icing
• freezing rain
• volcanic ash
• radioactive cloud.

The period of validity of a SIGMET message is no more than 4 HR, or no more than 6 HR for SIGMET messages issued in case of volcanic ash clouds. SIGMETs are relayed to aircraft in flight by the appropriate ATS units in the Amsterdam FIR.

8.3 AIRMET

An AIRMET will be issued by MWO De Bilt when a sudden deterioration in the meteorological conditions occurs that could endanger the safety of flights below FL 100 as well as those conducted by visual reference to the ground. An AIRMET is only issued when the sudden deterioration is not present, or forecasted in the GLLFC (see paragraph 4.2.2).

AIRMETs are broadcast or supplied by direct transmission to aircraft in flight by the Flight Information Centre Amsterdam (callsign 'Amsterdam Information' on 119.175, 124.300 and 128.500). These warnings are provided in the English language and will be identified as 'AIRMET'.

9.1 Internet

A dedicated web site (www.aviationweather.nl) is available for subscribed aeronautical users, requiring username and password. These can be obtained from the following user organisations: AOPA Netherlands, DARPAS, KNVvL and VNV (Dutch ALPA). Professional users residing in the Netherlands may contact KNMI (preferably through their employer) on [email protected].

The website (www.aviationweather.nl) contains all relevant and available meteorological products, information and services for aeronautical stakeholders, including pre-departure self-briefing information.

This website contains the following information:

• OPMET ((AUTO) METAR, TAF, AIRMET, SIGMET and advisories)
• Weather radar
• Satellite
• SIGWX charts
• Upper wind and upper-air temperature (UWT) charts
• Surface (Europe)
• Time series
• Temp profile
• AMSTERDAM/Schiphol Airport:
  1. Probability forecast Schiphol;
  2. Take-off forecast Schiphol;
  3. 5-Day weather forecast Schiphol.

The website furthermore offers dedicated areas with information for North Sea operations, general aviation, ballooning and hang gliding. This includes a weather bulletin (Dutch only) and Graphical Low-Level Forecast (GLLFC).

9.2 Teletekst

For low-level flights (including VFR) over the Netherlands, MWO De Bilt issues daily 5 or 6 weather bulletins in Dutch, with (AUTO) METARs of various reporting stations in the Netherlands.

The weather bulletins and (AUTO) METARs are made available via the Dutch public television teletext system ('Teletekst'), page 707. The teletext pages are also accessible via Internet (https://nos.nl/teletekst).

The bulletin contains a concise description of the most important weather systems affecting flight conditions over the Netherlands and information about the following elements:

• significant weather (incl. icing and turbulence except when occurring in convective clouds);
• clouds;
• thermals;
• height of the zero degree Celsius level if lower than 10 000 FT;
• surface wind;
• upper winds and temperatures at 500, 1500, 3000, 5000 FT or FL 050 (depending on the transition level) and FL 100.

An amended weather bulletin will be issued if significant changes in the weather conditions occur.