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This is from a video game or cartoon or something? Um, the katakana is for emphasis here. Usually it's for foreign words and sounds but sometimes it's used for the Japanese equivalent of italics. Since it's in katakana instead of using hiragana and kanji, I'm gonna guess the meaning but it's probably right.

Tekishuu chigau yo! Asa kita yo!

It's not an enemy attack! It's the sunrise! (or the morning has come!)

"yo" at the end makes it informal, more casual and personal. It is kinda hard to translate that by itself, you just have to make sure the translation feels personal and informal. So I used contractions.