Weak Air Runes need a Skystone along with a Blank Rune and a Silver Ingot to make one Weak Air Rune.
Weak Runes can be crafted at level one at the Rune Altar.
You need three of these to learn Whirlwind Blast and you will need extra to cast the spell.
The command to make a Weak Air Rune is [nya!rpg rune altar weak air]. For more info use [nya!info weak air rune].