The Shower Cascade is a shape
distortion of the three ball Shower in which one ball is thrown in the
opposite direction of a normal Shower, giving the pattern a Cascade-like
shape. This throw, called a Tossout, forces your receiving hand to cross
underneath your throwing hand, making the horizontal passes more difficult
than those in a regular Shower.
To learn the Shower Cascade, start by juggling the standard Shower. Then, make a throw from your dominant hand (which should be making the high throws) in the opposite direction of all the others, such that it travels away from your non-dominant hand. You are then going to make another, normal, throw from your dominant hand. As that throw is being made, your are going to start crossing your non-dominant hand underneath your dominant hand, preparing to catch the outward ball. As you are bringing that hand over, make a horizontal pass to your dominant hand, and then catch the outside ball. Stop juggling at this point.
Make sure you are comfortable with both the Tossout and subsequent horizontal pass, since these throws will need to be done without hesitation. To run the full Shower Cascade, you are going to make a normal Shower throw from your dominant hand after your non-dominant hand has caught the tossed-out ball. Then, you are going to uncross your non-dominant hand, passing its ball to your dominant hand as they pass by each other. You can then resume juggling the normal Shower.
That's pretty much all there is to it. The full Shower Cascade has a Tossout after every two throws, so the same ball will be used each time. This pattern looks best when the Tossout is almost equal in distance from the throwing hand as the normal throws are, since that most closely imitates the two arches of the Cascade pattern.