Matt Frank was drifting off to sleep in his second-floor apartment in Chelsea Tuesday night when his phone started making a loud noise and vibrating so much that it fell off a table and onto the floor, dislodging the battery.
His Samsung Galaxy, like cellphones throughout the Boston area, was triggered at about 10:38 p.m. by a “severe alert” from the National Weather Service that warned people to watch for flash flooding until 12:30 a.m.
“I was expecting a hurricane because the phone reacted very violently,” Frank said Wednesday. “I didn’t realize my phone could vibrate as much as it was.”
Thousands were as startled as he was. The alert — designed specifically to be noisy and jarring — was received by many cellphone users in the area for the first time.
“I thought my smoke detector was making weird noises, and then I realized it was my phone and wondered if I had accidentally set an alarm,” Stephanie Liu, an Allston resident, wrote in an e-mail to the Globe. “After I saw the alert, my reaction was ‘Seriously? Flooding? That’s it?’ ”
‘I have received the alerts and it makes me jump a little bit, but frankly, that’s what they’re intended to do.’
Yes, an entire region, on alert for a half-inch of rain. No flood damage was reported.
The alert came through the Wireless Emergency Alerts program, established by the federal Warning, Alert and Response Network Act of 2006. Wireless carriers who volunteered to participate in the program launched the service on April 7, 2012, but many people have only now upgraded to newer cellphones equipped with a technology known as cell broadcast, which delivers the messages, officials said.
The alerts look like text messages but are delivered through a system that’s separate from standard mobile voice and texting services, officials said. Wireless subscribers are not charged for the alerts they receive, according to the Federal Communications Commission.
The alerts also include a required audio signal and vibration cadence that is spelled out in federal regulations and designed to be helpful to people with hearing or vision-related disabilities.
“The first time someone receives an alert it may cause a little bit of surprise. It may startle people,” Brian Josef, assistant vice president for regulatory affairs at the trade group CTIA-The Wireless Association. “I have received the alerts and it makes me jump a little bit, but frankly, that’s what they’re intended to do.”
Tuesday night’s warning worked, in a fashion. One person posted to Twitter Tuesday night that he was playing the video game “Watch Dogs” when the alert came and thought it was part of the game. Another Twitter user called the alert “demonic.”
State and local public safety officials, the National Weather Service, the National Center for Missing and Exploited Children, and the president are authorized to issue the alerts, according to the Federal Emergency Management Agency. Most phones can be easily configured to block many of the alerts, though any alerts issued by the president will go through no matter what, the FCC said.
The messages are broadcast through cell towers located where people face a potential emergency, and the system doesn’t track people’s personal information, officials said.
“They don’t know that you’re there,” Josef said. “There’s no tracking of personal information, no tracking of people’s locations.”
Massachusetts used the system last April instructing residents to shelter in place while authorities searched for Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev, said Chris Besse, the Massachusetts Emergency Management Agency’s preparedness coordinator.
The National Weather Service started using the system in June 2012. It sends alerts to warn people about tsunamis, tornadoes, hurricanes, typhoons, dust storms, extreme wind, and flash floods, according to a National Oceanic and Atmospheric Administration website.
The National Weather Service said the flash flood warning issued Tuesday night was directed at Suffolk County and parts of Middlesex, Essex, and Norfolk counties.
National Weather Service meteorologist Mike Gerber said the agency has had a lot of success using the system to issue tornado warnings. The agency credits the alert system in saving lives last year in East Windsor, Conn.
In that instance, a manager at the Sports World Complex soccer dome evacuated 29 children and five adults, including herself, to an adjoining building after receiving a weather alert on her iPhone.
Within two minutes, a tornado hit the dome, sending it across an interstate highway. The children and adults, however, were safe.
A flash flood warning can’t be as precise because the alert system can’t pinpoint people’s whereabouts, Gerber said.
“Flooding is one of our nation’s biggest killers as far as natural hazards go. The issue is that it depends on where you are. The system doesn’t know if you’re on the roadway or if you’re on the 10th floor of an apartment building,” Gerber said. “It’s hard to satisfy everybody.”
For her part, Liu said the alert did spur her to act. She said she immediately looked up “disable severe weather alert” on Google and turned the setting off on her phone.