What is the grammatical form of "u'Vikati"?
Radak: It is Po'el Yotzei Shelishi (one causes a second to act on a third party); I will cause the wind to cleave [the wall].
Why does it mention Chemah and Af?
Malbim: Chemah is internal anger guarded in the heart. Af is anger that is revealed via punishment. When there is Af without inner Chemah, it is not evil. Af that comes via inner Chemah is evil! Even so, sometimes after the Af comes out and he is punished, the Chemah is assuaged. However, if the Chemah persists even after the Af went out, there is no hope. Our verse teaches that after via inner Chemah I will cleave a storm wind. When the Chemah goes out to be external Af, it will take physical form ? flooding rain. The anger floods everything ? unlike regular rain. Still, the Chemah is not assuaged; it is aroused again to become hailstones.
