Help with Alert and transforms

I have a mixed query, where I created a timeseries using a lot of transforms (Outter join, filters and organizating the data).

It is exactly what I want, however, I need to create an alert in this graph. Something like “if my value still above 1 for 15 minutes, send alert”.

I am used to create alerts but I have no idea about how i can use the transforms expressions in the Alert.

If i could associate the alert direct to the already built graphic, It would be the best scenario.

Any ideas, please?