The [au] diphthong. The first sound of this diphthong is once again a sound that does not stand on its own as a vowel sound in American English. However, it is very similar in sound to the aa as in bat. The way it is different from that sound is that the jaw on aa, aa, is tighter. And on aa as in ow, it drops more. In that way, it is similar to the ah as in father. Also, as you can see, aa, there's the lift here, and it's not quite as extreme in the 'ow', 'ow'. In that sense, the lips are also like the ah as in father. The tongue however, aa, ow, is similar to the aa as in bat in that it's raised in the back and then comes forward, and that's what you see.
The second sound is written as the uh as in pull. I do find, however, that it tends to taper a little bit towards the oo as in boo without the lips actually coming into that position.
I came back from vacation and found my flowers dead and brown. 度假回来发现我养的花已经死了，都变成棕色的了。