ATIS visibilities at Manchester

[Agaricus bisporus]

I'm sure the good folk at the "traditionally" smoggy destination of Manchester (UK) are proud of their fequently high vis, but why does their ATIS there know no ICAO reporting limit of "10K or more" as in teh rest of Europe at least, instead insisting on 20, 30, 40Km or even more?

Are they unique in this?

[chiglet]

If Met give 2500M or 60K, that is what we are told to broadcast. If however, the vis is 10K or more with nil wx and no reported cloud below 5000', CAVOK is broadcast, but then Met tell us its CAVOK
we aim to please, it keeps the cleaners happy

[kepor]

They're not unique, LHR do the same.

[cossack]

The connection is that the observations at both airports are still (but for how much longer is unclear) carried out by Met Office observers, rather than ATC staff using SAMOS (Semi Automated Met Observation System).

When ATC use SAMOS it will default (IIRC) to 9999 (10K+) when appropriate, whereas the human element will provide the empirical data and that is what is broadcast on the ATIS.

I think the Met Office like to record information as accurately as possible for their own records, rather than more generic data used by aviation and so the ATIS broadcasts will reflect this data.

On the subject of CAVOK, I remember a Big Airways pilot complaining that he'd told the passengers it was sunny because it said CAVOK on the ATIS. Fact was it was overcast at 5500 and we hadn't seen the sun for days!!!! I think he was a little embarrassed! Maybe we should report a "sunny CAVOK" or a "cloudy CAVOK"? :8