"Dawlish" wrote in message
...

For the main trough and its developing wave to drift so far North,
took forecasters by surprise; as did the intensity of the
precipitation that developed around the centre of the developing low.

So: not a great forecast, MO, late on the weather warning, but
entirely understandable. Its possibly down to data grid sizes and the
small area occupied by the "wet" part of that wave. The forecast
models just didn't have enough data to produce accurate forecasts of
precipitation intensity and location.

I don't think that's how or why it happened. The main frontal zone was split
with elevated storms tied to the forward upper front, effectively in the
warm sector, with further storms developing to the rear of this in and
around the shallow moist zone/near the surface front. Hence the wave, as far
as I can tell, wasn't the key player that it was originally expected to be
and didn't really develop over the UK. Also, given that much of the forward
precip. was falling into a relatively dry boundary layer surface totals were
likely to be low and not necessarily likely to trigger flash warnings.
Either way all the models that I'd seen struggled with the complexity of it
all and it looked like a very difficult day for those tasked with getting
the detail right.

00Z ASXX http://www.wetterzentrale.de/archive...ka20080428.gif
showing the split system.

Jon.