Answer: Evacuations are issued by the applicable governmental agency. The Community Association should get the word out to the residents, in case they have missed the notification. If you know of a resident with a handicap, encourage that person to be proactive about securing his/her safety.
Be sure you give your employees (if any) plenty of time to get home safely, and make their own preparations.
In the Spring, each year, the Community Association should remind residents to locate the nearest shelter, or secure a place where they can go if they are required to leave their homes. It is particularly important for individuals with special needs or pets to make advanced arrangements. Once it starts raining, it could be too late to get to the shelter of choice. Ask the residents to let you know where they will go, in case you need to reach them in an emergency.
Once the winds hit approximately 50 miles per hour, the emergency services are grounded, and cannot get out to rescue anyone who changed his/her mind about evacuation, when the building is surrounded by rising water and the electricity goes out.
Ultimately, you cannot force anyone to evacuate. The best the Community Association can do is be sure everyone is notified of the evacuation order, and that the elevators and possibly water will not be available, and so on.