"MikeB" wrote in message ...
2/ Does anyone know if the distance of 20% is a likely contributor to the
differences I'm seeing between the weather and my own measurements?
Hygrometers are weird things. I've got the opposite problem with mine, it
seems to under-read considerably. For example, it's saying 37% RH and an air
temperature of 10.9C at the moment, which gives a dewpoint of around -3C.
Yet nearby stations are reporting a dewpoint of 5C (Manston) and 4C
(Southend).

I don't know *why* the difference should be so marked, as the air
temperature matches Manston and the screen is shaded (and has the wind
whistling through it at the moment!)

The airflow's all wrong at the moment for low humidities by the way. You
need to look out for low dewpoints but with relatively high air
temperatures, which generally occur with a polar flow; clear skies and cold
air aloft are often a recipe for such low dewpoints.

If you use a site like this:

http://wxweb.meteostar.com/sample/sa...html?text=EGGP

you can find out what the forecast for dewpoints is from the GFS. The BBC
5-dayers have a humidity forecast as well, but it's a value for 12 noon on a
day rather than the detail you get from the above:

http://www.bbc.co.uk/weather/5day.shtml?id=2387

(both links for Liverpool)

As for climate tables regarding humidity, they're not really of much use: as
most of our weather is maritime in origin the averages will be quite high.
The best bet would be to look out for the sort of setups which give low
humiditied in your area.

NB - as you're in the NW you'll be looking out for different things than I
would here. For example, a polar NW'ly would give low humidities, yet up
there you'd get more in the way of moisture from the Atlantic. Local
knowledge is the key!