Monsoonal Flow of Moisture. By definition, Monsoon means the reversal of wind. The monsoonal flow is a flow of moisture that comes from the wrong direction. Usually our weather comes from the west. During monsoon season, it comes from the east or south. It usually pumps tons of moisture from the Gulf of Mexico across Texas, New Mexico and Arizona, but sometimes, the entire Rocky Mountain chain. This makes heavy afternoon thunderstorms for us.