A tornado is both. A calamity is a disaster. A tornado is a disaster that occurs naturally, and would thus be consideted a natural calamity or natural disaster.
Calamity is an event causing a disaster. There can be natural and man made calamities. Natural calamities are droughts, floods, etc. A man made calamity is war.
A thunder bolt is simply an incorrect name for a lightning bolt. And, since lightning carries much more energy than thunder, the "thunderbolt" is NOT weaker than thunder.
earthquake
Hurricane Katrina was a natural calamity because it was so catastrophic.
ampharos does not learn thunder bolt you have to teach it
A lightening bolt?
Flood
Pretty much, except the word "disaster" implies a much more serious situation then the word "calamity".
tm24
Usain Bolt
geological and natural calamity