Meteorological Observations from Offshore Installations on the Norwegian Continental shelf

The helideck operator for installations or ships that receive passenger flights must ensure adequate weather observations before landing and takeoff. Several new installations perform weather observations (METAR/AUTOMETAR).

For installations where METAR is required, a combination of METAR and AUTOMETAR are used. For some installations, METAR is provided during periods of flights and else AUTOMETAR.

At no significant weather, there is generally no major difference between METAR and AUTOMETAR. At significant weather, there usually can be found differences in visual parameters like visibility horizontally/vertically, clouds and present weather.

AUTOMETAR gives exact meteorological values at a specific point. By presentation of visibility and cloud base, the instruments will only provide data at the point they are located.

The following are well-known differences between AUTOMETAR and METAR:

1. AUTOMETAR generally presents lower visibility and cloud base than METAR
2. Differences can increase when the air mass is unstable
3. AUTOMETAR does not provide the cloud types CB and TCU
4. AUTOMETAR does not provide information about thunderstorms, graupel, pellets and hail
5. AUTOMETAR does not provide information about weather in the vicinity
6. NCD (No Clouds Detected) is only used in AUTOMETAR
7. NDV (No Directional Variations) is only used in AUTOMETAR
8. UP (Unknown Precipitation) is only used in AUTOMETAR
9. AUTOMETAR will always start with the term AUTO, stated after the date/time in the string
   
   

Overview of offshore installations with METAR/AUTOMETAR