"Dave Cornwell" wrote in message
...
|
| "MahFL" wrote in message
| ...
| Keith..what do you mean by the crucial 3 C dew point ?
| ------------------
| I'm not sure, but I got this rule of thumb from Will some time ago, which
is
| one of many rough guide criteria for snow (or not).
|
| Add together the Dew point and the temperature = A
|
| then if:-
|
| If A 7 prob. snow is very small
| If A=7 prob. snow = 10%
| A=6? 20%
| A=5 30%
| A=4 40%
| A=3 50%
| A=2 60%
| A=1 70%
| A=0 80% or more
|
|

The dew point is the much more important of these two figures and the
formula should be weighted in some way to reflect this. On most occasions
where I live, a temperature of 2C and dewpoint of 1C will result in rain,
perhaps a trace of snow in it if you look very hard. Temperature 3C,
dewpoint 0C will be snow most times. Combining these may produce the 50%
shown above for A=3, but does not really tell the story.

The temperature structure of the atmosphere above is also important. Last
week we had rain with A= -9!
--
- Yokel -
Yokel @ Ashurst New Forest
SU 336 107 17m a.s.l.

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