In March 2012, a tornado near Charlotte damaged or destroyed nearly 200 homes, injuring four people, including three children. In February 2020, a tornado near Demopolis, Ala., destroyed a mobile home, killing a 54-year-old substitute teacher and injuring her husband. In May 2022, a violent thunderstorm complex sweeping through Minnesota killed a 63-year-old volunteer firefighter when a grain silo blew onto his vehicle.

All three severe weather episodes share a common trait: They formed in areas of poor radar coverage known as “radar gaps,” where the closest radar is too far to reliably detect tornadoes, flash flooding, heavy snow and ice. That means people either were not warned by the National Weather Service about the dangerous conditions, or they weren’t warned until after the damage was done. The U.S. weather radar network is considered the most advanced in the world. But these gaps have persisted for years, in rural areas and highly populated cities, leaving millions of people vulnerable to severe weather as peak tornado season approaches next month.

Local and state officials, meteorologists, universities and the private sector have ramped up efforts to reduce radar blind spots, even after a 2020 Weather Service report to Congress that downplayed their significance. Those efforts, which in some cases began more than a decade ago, have been buoyed by pressure from lawmakers to close the gaps and by the availability of a new radar service from a tech company. In some regions, though, progress remains elusive.

“We’ve run into some roadblocks, partly because I think there’s denial of the problem,” Van Denton, chief meteorologist at the Fox affiliate serving North Carolina’s Piedmont Triad region, said in an interview.

Why, and where, radar gaps exist

Around the world, thousands of sensors constantly monitor weather — from the ground, ocean, air and space. Yet one meteorological instrument remains paramount for detecting hazardous, sometimes life-threatening storms: Doppler radar.

A Doppler radar sends a beam of energy into the atmosphere as it rotates to scan in all directions. The beam bounces off precipitation particles and back to the radar, helping meteorologists track precipitation, wind, thunderstorms and the likelihood or presence of a tornado.

The Weather Service operates a network of 143 Doppler radars covering most of the contiguous United States. An additional 16 radars are located in Alaska, Hawaii, U.S. territories and military bases.

There are dozens of regions, however, where the beam from the closest radar scans too high in the atmosphere to see certain types of severe weather. A radar beam travels in a straight line slanted slightly upward, while the Earth curves down and away from the beam. So the farther away the beam is from a radar, the higher in the sky it scans. Also, mountains can block the path of a radar beam.

In 2017, Congress directed the Weather Service to examine how low-level radar gaps affect warning accuracy. The 2020 Weather Service report acknowledged regions where the closest radar can’t scan below 6,000 feet — potentially missing tornadoes, heavy rain and other hazardous weather at lower altitudes — but found no “significant negative impact” on tornado- or flash flood-warning performance because “trained forecasters are able to overcome aspects of reduced radar coverage” by using information from satellites, models, storm spotters and other sources.

Ajay Mehta, director of the Weather Service’s Office of Observations, told The Washington Post the conclusions from that report are “still valid.”

Still, the findings surprised some meteorologists in the private sector and academia, who were critical of the report.

“I never agreed with the report at all,” meteorologist Craig Ceecee said in an email. Ceecee has identified more than 30 populated regions affected by low-level radar gaps.

He said there are populated communities — places with more than 25,000 or even 100,000 residents -— that could be at high risk for tornadoes, but where the closest radar scans at 10,000 feet or higher. “At that point, you’re looking two miles into the atmosphere, high enough to miss many tornadoes.”

Another meteorologist, Jack Sillin, looked at the relationship between radar gaps and race. He overlaid radar coverage and demographic data to show that the worst radar coverage in the southeastern United States tends to be in rural areas where the majority of the population is Black.

“The region is uniquely vulnerable to deadly tornadoes,” Sillin said in an email. “Fewer residents in the rural Southeast have easy access to well-built shelters in which to take refuge from tornadic storms. Thus warnings need to be issued farther ahead of time so residents can take appropriate action.”

North Carolina and other sites of notable radar gaps

North Carolina is home to what meteorologists have considered one of the nation’s most critical radar blind spots. More than 4 million people in the Charlotte area and the Piedmont Triad region, which includes the cities of Greensboro, Winston-Salem and High Point, live in a gap between Weather Service radars in Greer, S.C., and Raleigh, N.C.

On March 3, 2012, a tornado near Charlotte, without warning, carved a 3.2-mile path of destruction with maximum winds of 135 mph.The closest radars to that tornado, a 2 on the Enhanced Fujita scale, were 75 to 80 miles away. “Neither radar could scan below about 8,000 feet [above the ground] in eastern Mecklenburg County and thus could not detect any rotation developing in the lower part” of the storm, according to a Weather Service report.

The report noted that a radar located near Charlotte Douglas International Airport detected some signs of rotation, but that the radar signal was weakened by heavy rain moving over the radar site. That radar is among a separate network of 45 Terminal Doppler radars, so named because they are operated near airports by the Federal Aviation Administration. The terminal radars are designed to quickly pinpoint intense thunderstorm winds that can endanger aircraft, such as those that caused USAir Flight 1016 to crash on approach to Charlotte on July 2, 1994, killing 37 people.

Charlotte-area meteorologists have long relied on the FAA radar — installed 17 months after that 1994 crash — to try to see what the closest Weather Service radars can’t. But while a terminal radar scans low in the atmosphere — as low as 400 feet near Charlotte — its narrower beam is more easily absorbed by heavy rain, which can sometimes prevent it from detecting strong thunderstorms or tornadoes.

Another limitation of Charlotte’s terminal radar: It turns off its transmitter for a brief period in every 360-degree scan to avoid interference with a nearby communications tower, resulting in a slice of perpetually missing data to the northwest of the radar site.

Other publicized radar gaps include those in northern and western Alabama, southeast Arkansas, southwest Colorado, southeast Georgia, northern Iowa, northern and southern Kentucky, southern Louisiana, western and southern Minnesota, northern Mississippi, northeast Missouri, western North Dakota, northwest Ohio, southern Oklahoma, portions of Oregon, central Pennsylvania, western Tennessee, eastern Texas and central Washington state.

The gap in eastern Texas was the subject of an October broadcast by CBS19 in Tyler, Tex., in which the station’s chief meteorologist, Brett Anthony, recounted the May 25, 2015, EF-2 tornado that tore through Henderson with winds of up to 135 mph. No warning was issued until after more than 300 homes and businesses were damaged. The beam from the closest Weather Service radar, in Shreveport, La., “can be shooting as high as 3,000 feet” by the time it reaches Henderson, Anthony said, and as high as 6,000 to 8,000 feet to the west and south of Henderson.

In a 30-minute special report on west Alabama’s radar gap, Josh Johnson, chief meteorologist at WSFA in Montgomery, Ala., cited one deadly event as a prime example of the region’s lack of adequate radar coverage: the unwarned-of Feb. 6, 2020, EF-1 tornado near Demopolis that killed Anita Rembert.

“There’s no way to prove that better radar coverage in west Alabama would have saved Anita Rembert,” Johnson said. “But even the best [meteorologists] have to have good data, and in west Alabama we don’t have it.”

Gap-filling efforts gain momentum

The Weather Service has no more of its Next Generation Weather Radar (NEXRAD) systems available. NEXRAD, installed in the 1990s, “was a one-time government acquisition,” Maureen O’Leary, a Weather Service spokesperson, said in an email. That has communities affected by radar gaps searching elsewhere for solutions.

Colorado’s La Plata County and the city of Durant, Okla., in Bryan County are installing radars from Baron Weather, a longtime radar manufacturer and provider of forecasting services. Both jurisdictions received more than $1.5 million in state funding to help pay for the systems.

WJBF, the ABC affiliate in Augusta, Ga., is also considering buying a Baron radar, according to the station’s chief meteorologist, Tim Miller. The closest Weather Service radar is more than 60 miles away in Columbia, S.C., which “means that oftentimes, true severe weather is not detected over the Augusta area,” Miller said in an email.

Several universities have installed gap-filling radars in recent years, including the University of Missouri and Western Illinois University. The University of Georgia and the Georgia Institute of Technology recently teamed up to fill a coverage gap northeast of Atlanta, more than 20 years after a deadly tornado in Gainesville, Ga.

Rather than buying and maintaining their own radars, some TV stations and local governments have tapped into a service from weather tech start-up Climavision. The company has installed 24 radars in the United States since August 2022. The plan is for up to a dozen more by the end of this year and, eventually, more than 200 total throughout the country.

At January’s annual meeting of the American Meteorological Society, Climavision CEO Chris Goode presented examples of how the company’s radars recently detected a tornado, windstorm and snow squall not seen by the closest Weather Service radars.

“We’ve already started to see the positive results from gap-filling,” Goode said in an interview. “We’re seeing [weather] that simply can’t be seen by the existing infrastructure.”

WBTV in Charlotte; WTVM in Columbus, Ga.; WRDW in Augusta, Ga.; and WXII in Winston-Salem are among the TV stations that have subscribed to access radar data from Climavision, which has partnered with the Weather Company to “make its network of radars available to broadcasters on a market-exclusive subscription basis,” according to TVNewsCheck.

A Climavision radar installed in October in western Minnesota will be used by emergency managers in a region where, according to a news release from the company, existing radars were too far away to adequately see the May 2022 thunderstorm that killed volunteer firefighter Ryan Erickson, who was working in his car as a storm spotter.

Climavision announced an agreement last year allowing the Weather Service to access and evaluate its radar data. “This is an opportunity for our forecasters to have additional data that could potentially help them during the decision-making process,” the Weather Service’s Mehta said.

Other companies that have filled in radar gaps in the United States or internationally include EWR Radar Systems and Meteopress, which says it has developed a relatively lightweight and low-power radar that self-deploys in 11 minutes.

North Carolina gap not closed yet, meteorologists say

The radar gap near Charlotte was created in 1996 when the city’s Weather Service office was closed and its radar was moved to the office in Greer, S.C. That left a gap in low-level radar coverage in one of the nation’s fastest-growing metropolitan areas and a region that, for much of the summer, has one of the nation’s highest chances of severe weather.

“For the hole to be where the highest [severe weather] incidents in the whole country are, that’s a problem,” said Denton, the Fox affiliate meteorologist in the Piedmont Triad region. “We need something better to service 4½ million people. There’s a lot of people that are underserved.”

Climavision has installed three radars in western and south-central North Carolina. “So that gap is completely filled at this point,” asserted Goode, who noted that multiple media outlets and the North Carolina Department of Transportation are among those that have access to his company’s radar data.

Climavision’s radars operate at a higher frequency — in a range called the X-band — than the Weather Service’s S-band and the FAA’s C-band radars. The different frequencies have different trade-offs. X-band radars transmit the weakest signal and have the shortest range, but their higher frequency allows them to detect finer details in precipitation and wind. They are also the smallest and least expensive, at about $1 million per installation according to Goode, compared with an estimated $10 million to install a single NEXRAD.

That combination makes X-band radars well-suited for filling gaps, Goode said.

Brad Panovich, chief meteorologist at WCNC in Charlotte, disagrees with Climavision’s claim that it has fixed the radar gap there. “I am very familiar with the Climavision business model and plan and applaud their idea, but it definitely isn’t solving the issue at least not yet,” Panovich said in an email. “The Climavision radars are … very weak and have a limited range.”

Panovich also expressed concern about restricted access to Climavision radars.

“The problem with private for-profit data is that not everyone gets access to the information,” he said. “One TV station or one [emergency management agency] getting the data doesn’t help the public as a whole.”

Panovich and Denton are among several meteorologists who formed the North Carolina Radar Project group more than a decade ago. The group’s goal, according to Panovich, is to secure gap-filling radars through federal or state grants. Panovich said he is hopeful the group’s efforts will “be able to close this gap with public data and radars soon.” He contended: “Everyone should have access to these tools, not just the highest bidder.”

Lawmakers push for better radar coverage

The North Carolina Radar Project group began reaching out to lawmakers after the unwarned-of March 2012 tornado near Charlotte. The group’s efforts helped lead to legislation in 2017 requiring the federal government to study options for improving radar coverage, which led the Weather Service to lower the beam of some radars.

That brought the beam height in parts of North Carolina down to 6,000 to 7,000 feet, from 10,000 feet, Denton said. But “we know that many [tornadoes] happen in the lower 4,000 feet, so we’re missing those.”

The Weather Service has lowered the beam at 24 radar sites throughout the country and plans to do so at a few more sites by the end of this year, spokesperson O’Leary said. In Louisiana, the agency is moving a radar from Slidell to Hammond and will lower the beam in the process. The move, expected to be complete this month, is expected to improve a longtime gap in the Baton Rouge area without negatively affecting coverage elsewhere.

Rep. Jeff Jackson (D-N.C.) introduced a bill last July that would prioritize locations far from existing radars as the Weather Service deploys its next generation of radars, although that’s not expected until close to 2040. Another bill, introduced by Rep. Nathaniel Moran (R-Tex.), seeks to “expedite the implementation of solutions in areas where NEXRAD coverage must currently be supplemented,” according to a Moran news release.

Efforts to close the radar gap in western Alabama have the support of Sen. Katie Boyd Britt (R-Ala.), who described in a hearing last year how her family survived an EF-4 tornado that struck her Tuscaloosa home in 2011. “This is personal for me,” Britt said. “I know firsthand that minutes matter, but so do seconds.”

Britt is working with Reps. Terri A. Sewell (D-Ala.) and Robert B. Aderholt (R-Ala.) “to meet this critical need, particularly in West Alabama,” a spokesperson for Britt said in an email.

The Weather Act Reauthorization of 2023, a bill under consideration by Congress, contains several provisions aimed at improving radar coverage now and in the future, including “evaluation of commercial radars with the potential to replace or supplement the NEXRAD system.”

Next steps for the Weather Service

The Weather Service is in the midst of a $150 million program to upgrade its NEXRAD network, originally installed at a cost of $3.1 billion with a design life of 20 years, with the goal of extending the equipment’s lifetime until at least 2035. The four-step process, which requires each radar to be taken offline for up to two weeks at a time, began in 2015 and is scheduled to finish this year.

Phased array radar is one technology the Weather Service is considering as a successor to NEXRAD. Phased array antennas scan electronically with no moving parts, unlike the rotating antenna of NEXRAD, allowing for faster scanning of the atmosphere and more-frequent updates.

In the meantime, a recent report by a federal advisory board warned that “Americans are at risk now due to gaps in, or poor, radar coverage especially in traditionally underserved communities,” and it recommended that the agency “act immediately” to implement a gap-filling radar strategy.

“The next generation of radars will roll out in approximately 10 to 15 years,” Mehta said. The Weather Service “will continue to evaluate options that improve coverage in the interim.”