On 28 June, 08:43, Dawlish wrote:

They are not difficult to put out; that's the easy bit, all that has
to happen is the trigger of a threshold i.e. the forecasters have to
believe, through their experience, that something will have x% chance
of occurring. The difficult bit is actually getting the warnings
correct by the outcome of an event happening in a particular area -
that's the difficult bit, especially in convective situations.

When convection on days such as this can pop up quite randomly, I'd
love to see your methodology for assigning a probability to the chance
of convective precipitation, I really would.

I would think the MetO have more chance of getting their heatwave
warnings correct, as it is far easier to forecast temperatures above a
threshold, that it is to forecast rainfall above a threshold. I would
have far more belief in a temperature forecast than I would have in a
convective forecast for my area (and my area is NOT the whole of
Devon!!).

You expect them to forecast convective precipitation for your town?
Goodness me - you're a hard man to please. Yes, they'll have more
chance of forecasting temperatures for this week correctly than
convective events.

The MetO is not yet capable of forecasting convective events
accurately, at any distance greater than a very short time (for which
you could better use a freely available weather radar and watch the
sky as to when to move your BBQ indoors, or abandon the beach), either
in terms of 1. location, 2. intensity of rainfall, or 3. duration of
rainfall. Again, that is not a criticism, the tools are simply not
there to do that with good accuracy, it's just a fact.

The Met Office is capable of forecasting convective events accurately,
just not all the time. Have you ever looked at any diagnostics for
convection like CAPE? The key letter here is the P. Potential. The
whole of England and Wales was no doubt under a region of high CAPE
yesterday. In some areas, the surface air parcels were able to break
through the usual summertime capping lid on instability and form
thunderstorms. Did you not see the other thunderstorms on the radar in
the Reading, Birmingham, Manchester etc. areas? I would have though
the people in these regions would have been grateful for the severe
weather warning. And yet you see it as a chance to point out the
failings, which probably says more about you than the severe weather
warnings themselves, if I may be rude.

MetO forecasters are some of the best in the world, but accurate
forecsating of those 3 perameters in these events would be beyond
almost anyone (forecasting of convective events in the mid-west of
America may provide the exception to "anyone". Maybe the threat to
life from tornados forces more resources and a higher level of skill -
just a thought). Yesterday's too wide severe weather warning, that
you've referred to, shows that yet again. There have been a number of
other examples already this year.

Forecasting the location, intensity and duration of individual
convection cells would probably need cloud-resolving (1km
resolution?) models. The best mesoscale high-resolution models will
struggle to get them. Until then, you'll have to accept that blanket
warnings will be the way of things. Expecting these perameters (sic)
to be bang on - well, you're in cloud cuckoo land my friend.

I must say, I do think the post mortem explanations are a good idea,
though.

Or, in the case of the heavy rain mid-June, an explanation for their
forecast and the reasoning for their (correct) severe weather warning.
Funny how I never see you on here praising the forecasters for a
correct forecast. Always up for a gripe though, aren't we.

Richard