Twitter has announced that they have launched a new feature called "Twitter Alerts." The alerts are designed to be a bit different than a normal tweet, and have been put into place to help organizations to get accurate information out during emergencies.
During a crisis or emergency situation, credible organizations, such as government agencies like FEMA or the like, can make a bigger impression on the timelines and mobile devices of users. An alert is different than a normal tweet in that it is highlighted with a small orange bell (see image) and will also send a notification to a user's phone via SMS. If the user makes use of Twitter for iPhone or Twitter for Android, they will also receive a "push" notification.
The idea behind the alerts is also to help fight against misinformation as the alerts will be coming directly from an authoritative source. You can sign up for these alerts by going to the account's setup page. Here's an example ... https://twitter.com/fema/alerts