Configuring alerts to send as each event crosses the goal line

I dont think I quite understand alerts. I have something that looks like this:

I have alerts sending every hour, but it seems that the alerts send every hour after the threshold is breached - I only want the alert sent once something crosses the goal line once, not for every hour after. The next alert should be when the next item crosses the line. Any suggestions here?

I'm assuming the only way to do this is to scope the alerts window (through the query) to just the current hour. I'm not a huge fan of this because I want to see the past history of alerts - I guess the workaround to that is to duplicate the graph and scope one down to the last hour (and have that one send alerts) and let the other one show the history (but don't enable alerts on this one).

Exactly, scope the query to the time you want the alert to fire, and then build another query you can use to see the historical data

Thanks - appreciate the confirmation here.