"Martin Rowley" wrote in message
. ..
"Will Hand" wrote in message
...

"Joe Egginton" wrote in message
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Why is it that when the temperature is at 0c, it says fog instead of
freezing fog?

Just because the temperature falls below the melting point of water it
does not mean that fog magically turns into freezing fog. Freezing fog is
*NOT* fog with a temperature below zero, despite what some say. For fog
to be freezing fog it has to be depositing rime. I have had this argument
before, as a professional observer many years ago in still air we had a
fog with a temperature just below zero, I was told off for not calling it
freezing fog, but I stood my ground as all surfaces were wet despite the
temperature, in no way was it rime icing.


... I agree with you Will, but unfortunately, according to ICAO, if the
air temperature is *below* 0.0°C, then it *has* to be coded (in the METAR)
as FZFG. I believe that for the SYNOP, then the 'old' rules still apply,
i.e., 'fog depositing rime' etc. However, with more AWS coming on stream,
I suspect the ICAO definition will win out.

Martin.

I fear you are right Martin. It's all very very sloppy. AWS are so annoying
sometimes as they don't do cloud type and when you are forecasting
convection there is no way to distinguish cumulus types.
Cameras and satpics have their place but you cannot beat the MK1 eyeball for
a lot of things still.
Very sad.

Will
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