View Single Post
  #7   Report Post  
Old March 1st 18, 08:37 PM posted to uk.sci.weather
Norman Lynagh[_5_] Norman Lynagh[_5_] is offline
external usenet poster
 
First recorded activity by Weather-Banter: Jun 2016
Posts: 4,898
Default Why only a trace?

Graham Easterling wrote:

On Thursday, March 1, 2018 at 10:21:42 AM UTC, Norman Lynagh wrote:
Graham Easterling wrote:

On Thursday, March 1, 2018 at 9:57:57 AM UTC,
wrote:
Why is seemingly the whole country reporting only a trace of
rainfall, or even none at all? I had 7.1mm in the 24 hours to
0900 this morning, with 13cm of snow lying.

Ian Bingham,
Inchmarlo, Aberdeenshire.
80m asl.

It's because humans are now largely redundant in the system.

That's progress!

Graham
Penzance


Even a manual rain gauge is of no use in the sort of conditions we
have here this morning. The funnel fills to the brim with falling
snow and drifting snow then anything further just blows off.
There's no 'level' snow from which to calculate a probable rainfall
equivalent. This morning I simply gave a sensible estimate based on
the amount of precipitation that I observed. It might be an
accurate estimate or it may not but it's the best I can do. The
last tip of the AWS bucket was at 1540z on 27th Feb. Some sunshine
that afternoon had caused a little melting of the snow in the
funnel.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
Twitter: @TideswellWeathr


Yes, the problem with yesterdays snow was that it can in very heavy
bursts, which filled the funnel, then strong 30mph gusts blew it out
again. It's not a problem I normally come up against! Even when it
does snow here it's normally wet & sticky.

I suppose 1 way is to extract an area of snow, of a typical depth,
with the diameter of the rain gauge, and melt it?

Graham
Penzance


Yes, that's the theory. You plunge the inverted funnel into the snow
and melt what is collected. However, that only works if there is level
snow. Here, we've had dry, powder snow and strong winds. Surfaces
exposed to the wind are blown almost clear while shelterd spots have a
large accumulation of snow. Nowhere is there a representative 'level
depth'. I think a 'sensible estimate' is the best solution.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
Twitter: @TideswellWeathr