Translation:The flower bloomed yesterday.
It's not really a 'gah!' sound in Japanese, it's more of a nasal 'nnnga' at the back of the mouth, with a really faint g. So it has a bit of an n sound to it that you might mistake for 'ha' or 'wa' too
Depending on your accent, you might do something similar when you say 'singer' in normal speech - if you can make the same sound without the 'si' bit (and end it with an a sound instead) that's pretty close! Depends if you already say that word with a pronounced g though