That's not really possible as far as I am aware. The game shows the current location of a dragon on the map, which is how an addon can track them. Harrowstorms are more like the old dark anchors and do not have anything like that. The best an addon could do is pick up on player reports in chat, which would require that players write their messages in a way that can easily be understood by an addon.
But from what I have seen, you can spot Harrowstorms from very far away anyway, so you simply have to wait somewhere in the middle of Skyrim and check the skies.
Use the chat and write something like
"any HS up?" into the zone chat. Normally someone will point to any active HS there very quickly.
I travel around from northern wayshrine to the north western and then the center. Takes about 1 minute if you just port between the WS, and you'll see the active ones pretty quickly this way.
You can also add this to pChats /msg command, like !hs and if you write !hs the longer message text is shown in the chat.