The National Tsunami Warning Center (NTWC) serves the continental United States, Alaska and Canada. The Pacific Tsunami Warning Center (PTWC) directly serves the Hawaiian Islands, the U.S. Pacific and Caribbean territories, and the British Virgin Islands and is the primary international forecast center for the warning systems of the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization in the Pacific and the Caribbean and Adjacent Regions.
The warning centers have Atom feeds available that can be monitored for product updates.
The Tsunami Warning Center messages relayed through Twitter’s Tweet-to-SMS service has been discontinued by Twitter of April 2020.
To continue receiving notifications when a tweet from @NWS_NTWC or @NWS_PTWC is sent, you must choose to be notified within the Twitter app on your mobile device and/or through the twitter.com website. Your personal account settings may affect your ability to be notified in this way.
For more on how to set up tweet notifications (push notifications) to your device, head to https://help.twitter.com/en/managing-your-account/notifications-on-mobile-devices and choose Apple or Android.
You may find additional information here: https://help.twitter.com/en/managing-your-account/enabling-web-and-browser-notifications
The UNESCO/IOC service will provide NTWC bulletins for seismic events greater than magnitude 6.5 . Other tsunami warning centers provide information to this list also
National Weather Service Systems
Other Federal Systems