I have read numerous posts that refer to hoar frost. What is the
difference between hoar frost and "regular" frost. Is there one? Why
use the term "hoar" at all?

In North America the word "hoar" is not used at all by citizens and
meterological services to describe frost.

Bob

I see the term is used in North America, at least in the USA, Bob. The
Glossary of Meteorology (American Met Soc) gives the definition as 'deposit
of interlocking ice crystals formed by direct deposition' The mechanism for
the formation of hoar is similar to that for forming dew, except that it
requires a surface temperature below zero. (Surface = of the medium on which
the ice crystal is growing, or the ice crystal itself once formed)
Frost is the general term for temperatures below zero, and can be
sub-divided into air, grass, ground, road etc, but can be dry without any
deposit.
White frost deposited by supercooled fog is termed rime.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.woksat.info/wwp.html
or
www.btinternet.com/~wokingham.weather/wwp.html
"mittens" wrote in message
...
I have read numerous posts that refer to hoar frost. What is the
difference between hoar frost and "regular" frost. Is there one? Why
use the term "hoar" at all?

In North America the word "hoar" is not used at all by citizens and
meterological services to describe frost.

Bob