On 16 Sep, 07:33, "Will Hand" wrote:
"Richard Dixon" wrote in message

...





On 15 Sep, 20:11, Nick wrote:

Seems to have been much worse in the central south (I'm in
Southampton) than the southeast. Mostly light but seemed almost
torrential for a short while around 6.30pm. I have to admit I'm amazed
at how active this system, which just seemed to be a minor trough on
the south side of the high, has been.

Given the linear nature of the rainfall, I am beginning to suspect
some of my favourite - conditional symmetric instability - might be at
play. Basically the sort of instability you get at thunderstorms but
along frontal surfaces that organises rainfall in narrow, intense
bands - however the alignment of the jet and the local temperature
gradient suggests that it might not be the case.

Certainly I can't remember a day since working in the City where I've
seen such heavy rain throughout the day. Surprised Clerkenwell was
only showing 15mm as per Phil's email just now.

Richard

I think you will find it was surface convergence at a slow moving front
releasing upper level instability.
I may be wrong of course.

As per above: by the end of my paragraph I'd kind of ruled it out as
the upper jet was in the wrong direction w.r.t. the surface
temperature gradient for it to be CSI, unless there was some sort of
reversal of the jet direction at lower levels !

Richard