General wrote:

"Stephen Davenport" wrote in message
...

But they are not saying that there will be significant rain with 95%
probability. They are saying that there is low probability (5% if you like)
of a heavy shower or thunderstorm at any location but that if that
probability should manifest the impact from heavy rain could be significant.
==========================

That's not how I read it. The rain column is headed 'Precip. (%)' which I
take to mean the probability of anything more than a few drops of rain and is
a figure that stands on its own irrespective of whether any warning is in
force. Yesterday evening this column was saying 5%, which seems plain enough
to me - no rain was expected. It's not saying that there's 5% chance of the
warned circumstance happening.

(This is just a quibble about a detail of course - the storms did eventually
move through, though nothing too noteworthy for the time of year - but it
seems to me just the sort of blatant logical inconsistency that brings the
warning system into disrepute.)

I suspect that your other point, ie that the warning and the forecast are
generated by two different processes is the explanation. The progress of the
rain and storms was, in the event, perhaps somewhat slower than looked
possible when the warnings were generated?

JGD

The biggest gripe I have is that the warning system is usually very static. It
gives a broad-brush catch-all warning that is left "current" without any notice
taken about what is actually happening. This morning is a perfect example where
there should be hourly, or even half-hourly, warning updates spelling out which
areas look like being hit in the next hour or two. It's not rocket science but
I suppose it does need manpower which costs money and so............

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.