This topic has come up a few times now, and Metcheck have now started
doing them, for example (you might need to select an area if you haven't
looked at it before):

http://www.metcheck.com/V40/UK/FREE/...ility_rain.asp

Could someone who understands this sort of thing confirm to this
neophyte that what they're saying is nonsense? Basically, they take the
10 GFS ensembles, and each one contributes 10% to the probability. So,
for Moray for Thursday morning next week - seven days away - all the
ensembles are currently saying it's going to be dry, so Metcheck's
probability of it being dry next Thursday morning is 100%. So it's an
absolutely certainty that it's going to be dry here next Thursday
morning? Is this tosh, or is this some other use of 100% that I'm not
familiar with?

They also seem to be using the term tercile for their 10 bands of
possible outcomes (Dry, 1-2mm, 2-3mm etc). I thought a tercile was
one-third of something. More technobabble?
--
Steve Loft, Glenlivet. 200m ASL
Weather and webcam:
http://www.livet.org.uk/weather