Cerez' triple burst arrow

An arrow of flames loosed into the air like it were from a bow (bow or otherwise is not needed to perform this spell). Once arrow makes contact it deals 2d4 fire damage with one second delay before an explosion. This one second delay followed by an explosion repeats for a total of three times. Each explosion deals 1d6 concussive fire damage in the same location the arrow was stopped. Add caster level to minimum damage (Max bonus damage +20 in this way). At caster level 20 math regarding the spell should look like this: 2d4 + 3d6 + 20