As hearth was billowing by means of residential neighborhoods within the Hawaii city of Lahaina final month, emergency managers for Maui County despatched out an evacuation alert that may blare on the cellphones of anybody close to the blaze.

“Evacuate your family and pets now, do not delay,” the warning stated.

But many individuals most in want of the alert stated the message by no means reached their telephones, leaving them scrambling for security as the hearth started roaring towards their houses. More than 100 folks died within the inferno, and a few survivors puzzled why they’d not been notified earlier that the scenario was uncontrolled.

“I probably could have saved my animals,” Barrie Matthews, 70, stated as she tearfully recalled her household’s determined effort to flee. “We just had to go. We had to leave five of my cats. I can barely live with myself.”

As extra households disconnect landline telephones and fewer households have entry to broadcast tv and radio, emergency managers have more and more targeted on wi-fi emergency notifications to immediately attain massive numbers of individuals. But that fashionable system has its personal limitations, counting on the resilience of cell networks and the proficiency of emergency crews throughout a patchwork of native companies.

Two weeks after the Aug. 8 Lahaina hearth, as Hurricane Hilary was threatening California, the San Bernardino County Sheriff’s Department discovered that it couldn’t ship a wi-fi evacuation alert to the group of Seven Oaks, the place a number of folks had been in the end left stranded and one stays lacking. The county cited a breakdown in its connection to the wi-fi alert system, which is managed by the federal authorities.

Jim Keeney, who lives in Seven Oaks and is without doubt one of the six individuals who opted to remain behind, stated the lacking girl, Christie Rockwood, would have “absolutely” evacuated if there had been an order from the sheriff.

“Somebody dropped the ball,” Mr. Keeney stated. “We would have left.”

The patchwork nature of the system was made evident once more final week, as Hurricane Idalia was barreling towards the Florida coast. As 30 counties introduced varied evacuation orders, some native companies pushed them out through wi-fi alerts on the federal community, however many didn’t.

Launched in 2012, the Wireless Emergency Alerts system was designed to permit federal, state and native authorities to ship messages about extreme climate, unfolding disasters and kidnapped kids on a single, uniform system. It has been used tens of 1000’s of instances and will probably be a part of a nationwide check of emergency warning programs set to happen on Oct. 4.

Unlike tv, radio, street indicators or social media, emergency managers can use wi-fi alerts to focus on particular neighborhoods with an alarm that may wake somebody from sleep or jar them to consideration.

Jeannette Sutton, a professor on the University of Albany who makes a speciality of catastrophe warning alerts, stated the system might be messy. There is little steering for companies on the way to formulate the alerts, to allow them to typically exit with lacking data or complicated directions. They are sometimes left to be despatched by emergency personnel who’re busy making an attempt to battle fires or management floods.

When the system is operated appropriately, Ms. Sutton stated, it acts like a siren in 1000’s of pockets, giving the authorities the power to warn the precise folks on the proper time. An improve a number of years in the past expanded how a lot textual content might be included in every alert, permitting for extra detailed steering on how folks can preserve themselves secure.

“It is vital,” she stated. “It is absolutely necessary. It does save lives.”

When officers in San Bernardino County encountered troubles with the federal wi-fi alert system, they as an alternative despatched a notification by means of a non-public software program supplier that despatched an automatic message to everybody within the space with a landline, plus a restricted variety of cellphone customers who had signed as much as obtain such alerts. Those opt-in programs are widespread across the nation, however usually solely a fraction of residences be part of, making the federal system that may attain all cellphone customers a simpler choice.

A spokeswoman for the San Bernardino County Sheriff’s Department stated the county was investigating why officers couldn’t ship a federal evacuation alert through the storm.

In Florida final week, hard-hit areas comparable to Citrus County despatched wi-fi alerts as Hurricane Idalia approached, warning of the hazard of a life-threatening storm surge and urging evacuations. “Move away from the water. Hide from the wind,” one alert from Citrus County stated.

But different counties that had evacuation orders in place didn’t notify folks by means of the federal wi-fi message program.

Hawaii has had troubles with its alert system earlier than. In 2018, the state infamously sent out a false warning of an incoming ballistic missile, leading to a federal suggestion that emergency administration companies conduct common inner drills to take care of proficiency on the instruments.

On Maui, the primary indicators of the afternoon hearth got here at round 3 p.m., when video confirmed smoke blowing down a hillside.

As the blaze started transferring into the neighborhood under, some residents started evacuating on their very own. Others stated they struggled to see what was occurring or the place to go, with some saying they assumed the smoke within the distance was a hearth that may quickly be beneath management. Soon, although, the hearth gained momentum and was igniting homes in its path.

Records present that it was solely at 4:16 p.m., after the hearth had begun transferring by means of city, that the county despatched an emergency cellphone alert. It was despatched to a portion of the city’s residential space east of the business district. But it didn’t cowl the Front Street space alongside the waterfront, nor the opposite neighborhoods to the north and south, that had been quickly overrun with hearth.

At her residence on the south aspect of city, Ms. Matthews stated she noticed the smoke to the north of her and started checking media sources for updates. She acquired in her automobile and flipped by means of all of the AM stations, then the FM ones, however they had been all on common programming. She went again in the home and flipped by means of tv stations however noticed no signal of hassle. No alerts popped up on her cellphone.

The county has stated it didn’t activate its audible warning sirens, fearing that individuals would suppose a tsunami was coming.

“I thought somebody would let us know what was going on,” Ms. Matthews stated. “There was nothing.”

Suddenly, she stated, the hearth was simply a few blocks away. She stated she and her husband scrambled to gather their many animals and her ailing father. But they didn’t have time to collect all of their cats.

Many residents stated they by no means acquired an alert. Others stated they did.

Emergency administration officers in Hawaii didn’t reply to requests for remark about how the Maui wi-fi alerts had been dealt with.

A spread of technological components can decide whether or not an alert will get by means of, together with whether or not a cellphone is within the zone focused, whether or not it was turned on and whether or not it had cell protection.

The age of a telephone may affect the way it receives an alert, as newer gadgets are calibrated to obtain alerts focused to extra particular geographic areas. On Maui, one resident with an older telephone obtained the Lahaina alert though she lived on the opposite aspect of the island and by no means got here close to the hearth.

Some residents with newer telephones had been close to the evacuation zone however didn’t obtain any alert, maybe as a result of they had been simply exterior the focused space. One such household stated they’d a number of newer-model cellphones with them as they had been driving down Front Street earlier than the hearth reached there, however none of them obtained emergency notifications; a a lot older telephone utilized by one in every of their kids did get an alert.

Some who obtained the alert stated it could have saved their lives. Breanna and Glenn Gill had been taking a nap on the Lahaina Shores Beach Resort when the emergency alert got here at 4:17 p.m., blaring on their telephones, waking them up.

Mr. Gill opened the shade of their resort room and noticed the hillside ablaze above them. They had been in a position to evacuate.

Residents reported that cellphone protection was spotty that day, because the city handled energy outages and excessive winds. Cellphone service within the space of Maui the place the hearth occurred is essentially depending on overhead fiber strains, and as hearth unfold, these strains had been broken.

An AT&T spokesman, Jim Greer, stated the fiber infrastructure that serves all wi-fi carriers within the space was burned. While strains are buried in lots of elements of the nation, Mr. Greer stated that the volcanic rock on Maui makes {that a} problem.

Ms. Sutton, the professor who makes a speciality of emergency alerts, stated it was vital to construct extra redundancies into the emergency alert system, take a look at burying cables to make it extra resilient and do not forget that the wi-fi system can’t be relied on alone to warn people who hazard is imminent.

“It’s one layer in the many potential strategies,” she stated.

Nicholas Bogel-Burroughs contributed to this report.