Oh, it sounds good!
There is the same situation in Los Angeles, the USA. However, the weather becomes hotter after the sun shines 2 days.
However, there is another shower on 4/29 and 4/30. Therefore, the weather seems still unstable in Hong Kong.
The latest news: the shower/rain is available on 4/29 and 4/30 owing to the low air trough. The weather property:
the shortly-sunny basis may be available that depends on the weather condition (in fact, this can be possible on 4/29 and 4/30); no moon is available during the night time. The sunny period ends on 5/5.
Some information is false and here is the correction:
Stop the sun on 5/4, instead of 5/5.
No shortly-sunny situation is valid on 5/4 because of the thick clouds + low air trough (lat) (#230) in South China.
We want rain, but definitely not the shortly-sunny on 5/4! Go rain only!! (*5)
Also stop sunshine on 5/5 owing to the rainny!
However, because the next high air ridge (#231) comes on 5/6, the weather on 5/6 is sunny instead of rainny. (Mostly sunny on the 1st day of the period?! )
The story:
The group of cloud-thunderstorm: Thanks the god! We cannot accept the shortly-sunny situation, so could this help?
The gods: Yes...
The group of sunshine: See you this Sunday!
hp7629: Stop the shortly-sunny and enjoy the rain!
How about the har (high air ridge)?
The gods: The har has not been formed yet, but it works on 5/6. Do not forget that there is no shortly-sunny (that) is allowed in Hong Kong on 5/5.
The sunny period ends on 5/5. 
(*5)