....Southampton area, persistent and often heavy from about 1545 to
1745, clearing up somewhat now. Seemed to develop in situ, though the
radar suggests it developed on the west edge of the precipitation
associated with the front starting to affect eastern parts and then
split off. Not forecast this far west during daylight hours anyhow,
just a forecast of "scattered showers". Seems to be a larger area than
just a shower though! The forecast has this split off area remaining
over the central south until about midnight and detaching more and
more from the main rain area which remains (as forecast) well to the
east, moving north. It is now associated with an "orange" warning on
the Met Office site.

Prior to the rain starting, mid level cloud appeared to thicken from
the east (the front, I guess) but then quite suddenly and without
warning a small shower to the east intensified rapidly.

What happened here I wonder?

Nick