ice storm vs violent storm

ice storm and violent storm both are nouns.

Word	Noun	Adjective	Verb	Adverb
ice storm	Yes	No	No	No
violent storm	Yes	No	No	No

As nouns, violent storm is a hypernym of ice storm; that is, violent storm is a word with a broader meaning than ice storm:

ice storm: a storm with freezing rain that leaves everything glazed with ice
violent storm: a violent weather condition with winds 64-72 knots (11 on the Beaufort scale) and precipitation and thunder and lightning

Other hypernyms of ice storm include storm.

ice storm (noun)	violent storm (noun)
a storm with freezing rain that leaves everything glazed with ice	a violent weather condition with winds 64-72 knots (11 on the Beaufort scale) and precipitation and thunder and lightning