How to Escape the Omoplata
The omoplata is a viable submission, but it's also frequently used as a sweep. Often times, you'll find yourself caught in the omoplata and faced with a choice to either give up position or give up the submission. While this is a no-brainer in general, there are ways to get out of the position entirely, largely contingent upon your skill at the escape itself, and your partner's reaction along the way. Here, we'll look at several viable escapes from the omoplata position, not just from the submission, and take a look at ways to improve your position once you escape.
The Hopover Escape
The hopover escape is generally the first escape to look for. This is best executed right when your partner starts to set up the omoplata, but before they have completely secured their arm around your back. Start by posturing your hips up in the air, using your forehead as base. Next up, the general concept is simply to hop over to the far side of your partner, but stepping over with one leg at a time is ideal at first, until you get the hang of the movement. After that, there is a fair chance that you can work to pass your partner's guard, ending up in side control.
Escaping Under (Tane Otoshi Style)
A second option (particularly once the previous hopover option has been prevented) is to go underneath your partner's body instead of stepping over it. The general concept is to slide under them as they latch onto you with their arm (no doubt being mindful to avoid your hopover escape). Because they are glued to you, it's easy to lift them off the ground just a hair. My personal preference here is to use a tane otoshi style leg positioning, expediting bringing your partner backward. From here, you may be able to "turn the corner" and pass their guard when you clear the submission attempt.
Turning In Escape
This escape is very technical, and can take even more advanced students by surprise. As your partner sets up the omoplata, once again you're looking to roll forward. This time, however, as you roll, you're either unable to step over (because they're ready to block you as you try to hop), or else you're much better at this escape. Once you execute a simple forward roll, the idea is to get your elbow to the ground, preventing your partner's switch to the armbar. From here, you simply need to turn in toward your partner and come up on top.
I'll never forget the first time I saw this move in competition. It was spectacular, and everyone stopped to watch this insane looking technique. As your partner sets up their omoplata, the main idea is to snag your own omoplata (much like the re-Kimura concept). As you find yourself on all fours, look back in between and behind your legs, and try to grab your partner's sleeve (or wrist, if it's no-gi). Now just execute your own shoulder roll forward; this will end up with you doing the omoplata, but your partner can also execute the same move on you; so it's ideal to get your own arm free as you enter into your omoplata.
Sweep, Sub, or None of the Above
Again, while the omoplata isn't really the highest percentage submission, it does tend to yield at least a sweep the majority of the time. Work on these escapes, and you can prevent both the submission and the sweep, and you may even be able to get your own submission during the transition, or at least improve your position once you clear the submission (or, rather, as you're clearing the submission). As always, please let me know how these techniques are working for you!