Synonyms for Alerting:

adj.

warning (adjective)
cautionary, threatening, warning, alarm, advisory.

n.

alerting (noun)
alertness, alert.
state (noun)
alertness.

v.

alarming (verb)
startling, panicking, surprising, signaling, frightening, shocking, Scaring, dismaying.
cautioning (verb)
forewarning, admonishing, enjoining, warning, Exhorting, Advising, Cautioning.
indicating (verb)
winking, Labeling, prompting, nodding, Beckoning, symbolizing, Motioning, waving, Nudging, branding, Betokening, Noting, Indicating, flagging, Shrugging, marking, Stamping, Tagging, Designating, guiding, gesticulating, pointing, Denoting, Notifying, Gesturing, cueing, Ticketing, pointing out.
warning (verb)
threatening, alarming.

Other synonyms:

Other relevant words:
alertness, alert.