A pregnant woman and her son died in a flash flood in southeastern Pennsylvania last Thursday after the National Weather Service issued a flash flood emergency for the region. She was on the phone with 911 as her car was swept away by the sudden rush of water.

Just days later, Tropical Storm Barry dropped 5-6 inches of rain on the Gulf Coast — far less than the 15-20 inches originally forecast to top the already swollen Mississippi River. Though flooding damaged homes and knocked out power to 153,000 people in Louisiana, the storm's effect was not nearly as devastating as expected.

There's a clear need for residents to take emergency alert warnings for flash floods and other disasters seriously, but with a shaky track record of predictions, forecasters are questioning how best to provide warnings that will not be met with skepticism.

The NWS, which sends out approximately 12,000 flash flood warnings every year, hopes that a new emergency alert system is the answer.

Preliminary numbers suggest that the new system — with a planned rollout beginning Sept. 16 — would pare down the number of warnings by about 80 percent, Mary Mullusky, chief of the agency's Water Resources Services Branch, said. The aim is to emphasize the most dangerous floods, as well as simplify the warnings so that they are easily understood and relatable for the people who receive them.

“People are becoming desensitized to the warning,” Mullusky said. “There were just too many and we were getting complaints about them. We wanted to be responsive to that and help people readily understand what the warning is and take the appropriate actions.”

Experts warn that flooding is the top weather-related killer in the United States. Approximately 6,000 people in the U.S. died in flooding or tropical cyclone-related flooding between 2004 and 2018, according to the National Oceanic and Atmospheric Administration. The cost of damage for those storms topped $825 billion.

The biggest killer, experts say, are people choosing to drive their cars through flooded areas.

One-year-old Oliver Kelly cries as he is carried off the sheriff's airboat during his rescue from rising flood waters in the aftermath of Hurricane Florence in Leland, North Carolina, on Sept. 16, 2018. Jonathan Drake / Reuters file

The impact-based warnings will fall into three categories: base, considerable and catastrophic. The latter two, considerable and catastrophic, which warn of floodwaters that could severely impact lives and property, will be the approximately 20 percent of warnings that the NWS will push out to people’s phones.

“There’s been a discussion going on in the weather community for at least five years now of the number and complexity of the warnings that go out,” said Rebecca Morss, a National Center for Atmospheric Research scientist who studies decision making in hurricane and flood risk communications and evacuations.

“There are different ways they are trying to simplify the system so that people can really identify the most important threat that they need to respond to," she added. "It’s especially important in a flash flood that can evolve really quickly.”

Residents wade through flood waters from Tropical Storm Harvey in Beaumont Place, Houston on Aug. 28, 2017. Jonathan Bachman / Reuters file

The NWS interviewed local leaders and storm survivors to best grasp how flood warnings helped or hurt communities.

Kim Klockow McClain, a scientist and researcher at the National Severe Storms Laboratory in Oklahoma, spoke to storm survivors to better learn how they had reacted to warnings in the past. She said the challenge still is to break down the information in a way that people can quickly understand and trust to use in their decision making.

“There’s a lot of challenge still in trying to communicate how flooding is going to evolve in ways that people can understand and relate to it," Klockow McClain said. "They have to understand and personalize it. They need to know where it’s going to occur, what it will look like and how it will unfold and evolve.”

Another issue that some worry about is that people who receive these warnings still won’t all react the same.

That was seen when Washington, D.C., recently received enough rain for the NWS to categorize the storm as a once-in-100-year event, causing massive flooding and triggering more than 70 water rescues between Washington and northern Virginia.

The new warning system aims to get the largest number of people to react safely to a disaster.

“How do you provide information that is succinct, easily available, accurate, and reflects the uncertainties of our ability to predict the future but still meets the needs of all people?" Morss asked. "It’s a really difficult question.”

It's one that will need to be answered, as climate change continues to affect the movement of water and weather forecasting.

“Flooding is absolutely not going away," Klockow McClain said. “It’s something we expect to continue to be a problem pretty much everywhere.”