Can Hex give disadvantage on initiative if cast before first round?

@JeremyECrawford if initiative is dex check, can hex give dis on initiative if cast B4 first round? Also do people know they are hexed? Thx!

— Tim D (@TheNamesNewanda) September 27, 2016

Hex, like most spells, can be cast outside combat. The target notices the spell when the spell's effects occur. #DnD https://t.co/3Y7shFrMkn

— Jeremy Crawford (@JeremyECrawford) September 27, 2016

@mblaine77does the caster know if the hex has taken affect? Yes.

— Jeremy Crawford (@JeremyECrawford) September 27, 2016