On Nov 9, 9:11*pm, John Hall wrote:


Isn't part of the difficulty with assessing these warnings due to the
fact that when they are issued some days in advance they inevitably have
to be couched in terms of probabilities? So they will be expressed as a
40%, 60% or 80% chance of the extreme event occurring in a particular
region. How do you assess in isolation whether a single such a warning
was correct? All you can do is take maybe a year's supply and see if
roughly the right percentage came to pass. (And even that isn't easy.
What if certain places in a region hit the extreme weather threshold but
others don't. I think that should count as a correct warning. But of
course not everywhere has a reliable recording station.)


Very valid points. We're molving into the sphere of 'risk
communication'.

Subjective on-the-spot verifications are very untrustowrthy - a
relatively benign day might be experienced in one's back garden while
10 miles up the road there is 40cm of snow. A regional warning of
disruptive snow would therefore of course be correct but viewed as
incorrect through the former observer's window.

Stephen.