Ugh, no you don't. Think about your users - I need some help, so I go to a help portal. The last thing I want is to have to click through to get to the place where I can ask. Give me the portal, immediately, with as simple an interface as possible.
If you insist on breaking the user experience, you could try to wedge some javascript into the announcement banner in JIRA. Something that can detect when it's rendering the portal page and pop up your "I want to get in the way of the user" job.
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