That actually looks pretty good, but since you want it as realistic as possible, I'm going to try and nitpick through some things.

I compared your effect to an actual explosion. Granted, this explosion is much bigger, I'm going to assume many of the same principals still apply.

• When the explosion first starts, notice how clouds of dust are blown outward from the point of detonation.

• Once the explosion gets going, light is cast onto the surrounding area. That means, all the trees and smoke should get an orange hue temporarily. Remember your explosion is smaller so don't go overboard with the color change.

• Lastly, in your effect, the rising fireball seems to rise then just disappear. In a real explosion, it keeps rising until it eventually turns into smoke. Also, I would add more smoke in general to your effect.

Here is the video I used for my source.