9th May 2012: Orographic enhancement over the Downs?

This was an interesting one - a moist south-westerly flow over the UK bringing another spell of rainfall to add to an already soggy April and early May. Image below from the excellent WeatherOnline site superimposes the surface pressure over the surface rainfall. I've highlighted three seemingly stationary areas of heavier rain that were there for over an hour at the time of writing:

Hopefully the 4 small black lines can be seen here that show the regions where the precipitation seem to be heavier than the surroundings. I've actually placed the lines to the south of the main areas of enhanced precipitation just to make them clear.

Initially I thought it was likely a radar artefact (and who is to say that this isn't the case?) but on closer inspection I got the impression that it might be some form orographic enhancement. Best thing to do here was to take a look at the underlying orography to see whether it was just the radar playing tricks with me

So to the left I also show the orography in the SE of England. I was surprised to see that the four stationary lumps of enhanced precipitation seemed to tally pretty impressively with  the orography of the area - at least in the true seeder-feeder mechanism on the upslope of the flow hitting the Downs. There even appears to be double-structure coincidence with the double-lump of the Downs equidistant between Slough and Brighton.
There was me thinking that orographic enhancement of the rainfall was just a thing of the Scottish Highlands, Wales and the Moors (if this is what we're seeing)....