Let's take a word of paal mould in English, and compare
[to] harass
harass [him]!
harass [him]?
In questioning, both vowels elongated compared to neutral tone.
In exclamation, I hear more like, h(e)rass! The second vowel in this example
is still a, but change to o is likely. Perhaps a-o shift is shortening
(kamatz-katan) rather than elongation (holam). The point, however, is
reduction of the first vowel. Try military commands, still clearer.