Not sure if this is a significant part of the mei yu process but noticed a decent build up of cumulionimbus out to sea today. You mentioned that it looked like rain and it felt like it should, it was so muggy, but i don't think we get much from that kind of weather - not like pingdong where it's probably a sure sign! Some nice lightning out to sea tonight.
Thinking of doing a driftwood market run to taipei this weekend - this is one of the trickiest times of the year to pick the gap up there. Get it wrong and it's not just a shower or two - it's a complete wash-out and then you run the risk of the su hwa being closed as well.

Seems to be a big stationary front dropping in on the weekend - just a matter of will it hold off for saturday at least.