Both the spells you speak of are spammable spells - if you have 300 mana and 25 MR. The effects that they are are more or less instant and have no duration effects. Thunderstorm does damage around a targeted area. Essence of wind does area damage around the caster. The arcane focus level will determine both the strength and the diameter of the spell effects.

But as with all SW spells they have a long casting time.