Indication
Noun and の adjective
ちょうこう
彼女は、私に下痢の兆候がきたと告げるやいなや、トイレに駆け込んでいった。
She told me that she had symptoms of diarrhea and rushed into the bathroom.
An omen for the climate of things is a sign or indication of change. If there's an omen, there's going to be a sign as well.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.