Create an Advanced Alert and on the Trigger tab you will simply need to create 2 filters:
1. Select Custom Node Poller from the top drop down first then click on the ... box to add a Simple Condition
2. From the Custom Node Poller section choose 'Poller Name' and then 'equals' select the 'hrProcessorLoad'
3. Enter a new Simple Condition that is the Custom Node Poller value you want to be alert to if greater than. I am not sure without testing whether it will be the 'Status' or 'Numeric Status' value to check against.