Twitter's Agenda Setting Power: Example of a Hail Storm

I just made it home from work yesterday right before a brief but vicious hail storm descended upon Austin. After checking the radar on TV and realizing I'd probably be fine, I turned to the important things in life - checking my Twitter feeds. And there I saw this:

Must be a hail storm in Texas right now. Mighty Twitter knows all.

Nothing too unusual considering the speed with which messages get spread through Twitter. Except that in this case, the tweeter was @pphilp and lives in Canada. It took me a second to realize that the hail storm must be a trending topic on Twitter and lo and behold it was:

How can an event this localized dominate the Twitterverse so easily? A number of possibilities come to mind: either yesterday was a very slow "news day" for Twitter, or there is a disproportionate amount of Twitter users living in Austin. Or maybe it's a combination of both? TwitterGrader does support the idea that Austinites might be particularly prone to tweeting - it lists the city among the top 10 Twitter cities. Maybe the tweets around events in Austin are more likely to make the trending list because there are simply a lot of Twitter users in Austin? Think about the power that gives Austinites and other tweeters from Twitter-friendly cities in terms of setting the agenda for what other Internet users hear and think about.

Whatever it may be, here's an example of an event that didn't make it past the local news in the traditional media (at least I'm not aware of any of the major networks running a story on the Austin hail storm, let alone the international media). Yet, Twitter spread the news of this localized event all the way to other countries - and all of that pretty much in real time.