The situation is called T-shower or T-storm because sometimes lati-thunderstorm, sometimes T-shower, and sometimes no rain at all.
The unstable weather happens because of the southwest mansoon or its property.
P.S. Stop sunshine tomorrow (8/23)! According to HKO, it is not possible for shortly sunny after the T-storm or T-shower. (*10)
Afterward, the sunshine reappears because the southeast mansoon or air flowing or its property substitutes the southwest one. Generally speaking, the southeast air flowing causes the high chance to have sunshine.
After I have thought, I beleive that some information that HKO has been providing for these days is wrong because of the weather changing.
Here are some:
1. There should not be shortly sunny appears with shower or T-shower on 8/23, according
to the definition of HKO.
2. No sunshine is possible on 8/24 and 8/25, but it is possible on 8/23.
What is wrong? Think hint: such sunshine with shower is valid after 8/26.