Met Observations for Aircraft

A big part of the job in the tower is passing meteorological observation to aircraft.

Whenever BAS aircraft are flying we collect and pass hourly weather observations for all airfields along the planned and alternative routes for the flight. These help the pilot decide whether to continue with the flight as planned, what altitude to fly at, what find of approach to make when landing. And probably other flying decisions that I don’t know about.

The observation reports typically include, wind speed and direction, contrast, horizontal definition, cloud coverage and heights, temperature/dew-point, present weather, barometric pressure and observer comments.
We pass observations in two different formats:
– A BAS field observation format
– Standard METAR

The content is similar, however there are some subtle difference. In the BAS observations wind directions are given as magnetic bearings where METARs give wind directions in true. The cloud coverage is reported in oktas (eighths) in the BAS observation while a METAR uses scattered, broken or few terminology. And the BAS observations include an indication of the contrast and the horizontal definition which are particularly relevant to polar flying.

BAS Field Meteorological Observations
Hourly Met Observations are taken at Rothera, Fossil Bluff and Sky Blu. The first observation is taken at 700am (1000 zulu). The Fossil Bluff and Sky Blu observations are taken on the HF radio and the Rothera observation we can get from the local intranet.

Hourly BAS Met Observation for Rothera
Hourly BAS Met Observation for Rothera

The BAS observations are mostly passed to flights heading south to deep field locations.
METAR Observations
This is an international standard for aviation meteorological observations. The airfields at Punta Arenas, Marsh and Mount Pleasant in the Faulkland Islands all provide hourly met observations in this format. These observations are typically passed to flights heading North to Chile or Faulkland Islands.

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