The T-55 Directed Energy Rifle/Advanced, or Storm Rifle, is the evolution of the standard Plasma Rifle and served various infantry during the violent Sangheili civil conflicts that followed the Human-Covenant war.
The weapon now includes a modular coil set, a high-mounted cooling shroud, and an extended barrel, all contributing to greater overall performance in the field than its predecessor.
As the name might suggest, the fully automatic weapon unleashes a "storm" of projectiles upon firing - rapid and deadly at close to medium range, but less accurate at longer ranges. However, it overheats within approximately 5 seconds of continual fire, though this is generally still plenty of time to deplete shields of and kill a number of hostiles.
It seems the Sangheili have traded the slower, yet more accurate and longer range weapons of the past for more aggressive variants, influenced by the Jiralhanae "brute force" tactics evident through such items as the Jiralhanae variant of the Type-25 Directed Energy Rifle.
The weapon also appears to be similar to the Plasma Repeater, though it lacks the former's ability to quickly vent waste heat.