"Norman" wrote ...

0630z NNE F1 7000 HZ 8Sc012 09.3/07.7 1017
[and]
Tudor Hughes wrote:

Is that really haze, Norman? I know I've got a bit of
thing
about "haze" and "hazy sunshine" but surely it's thin mist and not
solids in suspension.
[and]
"Norman" wrote ...
I tend to agree with you Tudor but, by definition, it's only
considered
to be mist if the relative humidity is 94 percent or more (or is it
more than 94 percent?). On this occasion the RH was only 90 percent
so
whatever was obscuring the visibility couldn't be called mist. That
left haze as the only option. Or have the rules changed since I
last
did "official" observations?
[and]
"Will Hand" wrote...
AFAIK it is still mist if RH equal to or greater than 95%, haze if
visibility reduced by water droplets and RH 95%.

.... that's certainly the "Observer's Handbook" guidance, but I seem to
remember that for practical purposes, we had a bit of latitude in
interpretation, but only by a few %. So U=90% and mist was *just*
about OK. The problem is ... does the screen environment accurately
match the 'open atmosphere' conditions?

Cause of many a 'happy' argument between shifts & also with the
station SSA :-)

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023