Public Safety

National Cell Phone Alert System Activated for First Time in San Diego

Some cell phone users in San Diego County were surprised today when their phones made a strange tone and warned them in a text message of a severe threat of flash floods.

It was the first time the national Commercial Mobile Alert System—or CMAS—had been activated in San Diego County. 


CMAS is a national emergency alert system that launched nationally this year as a joint service of the Federal Emergency Management Agency, the Federal Communications Commission and commercial wireless carriers.

It is expected to be a powerful emergency warning system, but some residents called the County and other local authorities Monday expressing confusion and concern over receiving a flash flood warning that didn’t seem to apply. 

County officials said Monday they will work with federal partners to review how and when the system should be used.

“When a disaster occurs, we will want to reach residents through this federal mass notification system,” said Holly Crawford, director of the County Office of Emergency System. “So it’s important that the messages are targeted to the right population.”

The service enables government agencies to use cell towers to send targeted emergency alerts. In our region, the National Weather Service, which activated its ability to use the system on June 28, is currently the sole agency using it. Later this year, the County Office of Emergency Services will add the ability use the system in emergencies.

The CMAS system uses cell phone towers to geographically target people in areas where the threat applies.

However, Monday’s flash flood warning was broadcast to cell phone users all over the region, even though the warning applied to just a few East County communities, where monsoonal thunderclouds opened up Monday afternoon.

FEMA officials told the Office of Emergency Services Monday that particular carriers had elected to send the warning only to customers in the affected areas, while other carriers had sent it to customers throughout the region.

The National Weather Service has said it will use CMAS any time it issues a Tornado Warning, Flash Flood Warning, Hurricane and Typhoon Warning, Extreme Wind Warning, Blizzard and Ice Storm Warning or Dust Storm Warning. Tsunami Warnings will be added soon, the federal agency said last month.

CMAS is designed to complement existing emergency notification systems. Locally, it would exist alongside AlertSanDiego, the County’s reverse-911 system that contacts the region’s landline numbers automatically, and also any additional numbers and email addresses people have registered.

Once the County is using CMAS, that system could reach residents who have not registered their cell phones with AlertSanDiego, but CMAS doesn’t replace the local system.


In fact, the County urges residents to register their cell phone numbers, email address, or any Voice Over IP phone number with AlertSanDiego today!