Tornado
noun, の adjective
A dragon scroll is a dragon that's shaped kind of like a scroll, spinning around. This is a tornado.
たつまき
The reading is the kun'yomi readings of the kanji. For 竜 just think about how it's a standing (立つ) dragon, because it would have to be if it's a tornado. Your まき reading comes from 巻く, but the kana is pushed into the kanji.
昨夜、竜巻警報が出て、停電にもなりました。
There was a tornado warning and a power outage last night.