sorry - i can't imagine how to get alerts automatically created via scripting in UM - as fas as i see in the documentation you can manager your custom scripts via "Manage Scripts" in your UM settings page - but these are only used if you define them in an already created or newly create an alert via GUI.
also the commands for um are very less you may use - in the manage scripts page you may use the questionmark button to show the help where you can find a section "Supported Unified Manager CLI commands" - and as you see there are not many of them and nothing about creating alerts via script.
so in your case it obviously looks like that there's no change to achieve the result you asking for.
sorry - eventually someone else has an idea on that.
AJ