Thunderstorm

Thunderstorm is a the primary spell for Elemental shamans.

Uses
Thunderstorm has multiple uses. First, it is a self defense mechanism that helps the elemental shaman to push melee attackers away and also damage them a bit in the process. Secondly, it is an instant mana restorative ability should the shaman encounter mana problems in long fights. Thirdly, Thunderstorm is one of the very few abilities in the game that has a knockback effect; this effect can be very useful in many situations in PvP (and select PvE Situations) because it can be used to push an enemy player off cliffs or higher elevated places resulting in fatal fall damage unless the opponent has some countermeasure to save themselves. Notable examples are the lifts in Thunder Bluff, the Lumber Mill in Arathi Basin, the zeppelin from Orgrimmar to Thunder Bluff, or the Meeting Stone for Naxxramas. The flag spawn point in Eye of the Storm is perhaps the best place to use this ability in the game. Due to the layout of the area, a well timed Thunderstorm can easily kill crowds of enemy players and prevent the flag from being picked up.

PvE Uses
Although the Knockback severely limits the spell's usefulness in raids and other PvE situations (Knockbacks are generally considered a nuisance to tanks), there are still places where the Knockback is welcomed:
 * In the Faction Champions encounter, the Knockback works against the enemies, and is a useful self defense mechanism in that fight. Throwing a champion back away from you decreases the amount of time they're hitting you before their aggro resets every few seconds.
 * In the Deathbringer Saurfang fight, the Knockback is effective against the blood beasts (although the damage is still considered AoE, and thus negligible), giving you and other ranged DPS a few more seconds to beat on the beast before running around is required.
 * Gluth of Naxxramas; using Thunderstorm to knock back the Zombie Chows as they move towards Gluth can buy a few more seconds. However, extreme caution must be used, as a misplaced Thunderstorm will throw the zombies straight into the jaws of Gluth instead.

In any case, adding Glyph of Thunderstorm adds 2% more mana to the mana given, and removes the knockback, making it a perfectly viable spell to use during AoE Trash pulls, along with the Magma Totem/Fire Nova combo.

The gained mana is always useful in long, hard burn fights.

Improvements

 * Concussion: Increases damage done by 2/4/6%.
 * Elemental Reach: Increases radius by 10/20%.
 * Elemental Fury: Increases critical strike damage by 100%.
 * Glyph of Thunder: Reduces the cooldown by 10 seconds.
 * Glyph of Thunderstorm: Increases the mana recharged by 2% but removes the knockback.