for Tornado, it's simple: take Summon Air Elemental, enhance it, and that's it – Tornado is ready.
watch the video; the mod author shows off new spell effects. In principle, everything is clear there, and you can repeat something if you really want to (by the way, I saw the Tornado in his mod).
https://www.moddb.com/mods/homm-5-chaos-theory/videos/divine-wrath#imagebox