When I say the first syllable of “power” (i.e., the pow, rhymes with cow), the "ow" sound (represented by
aʊ) requires me to make a shift with my mouth. In slow motion, it would start with the
pa sound (as in "pal"), with my mouth open, and then my mouth would need to form a small 'o' with my lips, as I began to say the "w" sound (
ʊ). So, the answer to your question is yes, I go 1-2-3 as you have diagrammed it. But this is a rather "advanced" way to look at vowel pronunciation; I think most natives do this without thinking about it.