Our Perfect Storm

Forecasting the weather in Los Angeles is an enterprise one could imagine the Existentialists dreaming up to torture one of their protagonists. For eight or so months of the year, of course, there effectively is no weather here. The absurdity is compounded when you consider that L.A.’s TV news outlets engage in an arms race for Doppler weather-radar superiority when night after night those radars sweep the L.A. basin for a tempest, but the meteorological teapot is almost always calm. Fittingly, one of the city’s veteran weather forecasters, KNBC’s Fritz Coleman, moonlights as a stand-up comedian.

“It’s challenging for us because you’ll sit for days, weeks, with very little going on, and admittedly it’s not the hardest thing to do,” says Tim McClung, a meteorologist at the National Weather Service’s Oxnard station.

But during L.A.’s just-ended rainy season, from mid-November to mid-April, McClung and his colleagues nevertheless get their crack at what airline pilots call “significant meteorological events.” And then, once in a great while, a legendary force is unleashed.

“You wait and wait and wait,” McClung says, “and finally a big storm will come in.”

The thunderstorm that inundated South-Central Los Angeles the afternoon of Nov. 12 with more than 5 inches of rain in two hours--and, most spectacularly, left behind a freakish blanket of hail that resembled Fargo in February--was beyond legendary. Thunderstorms are famously scarce in Los Angeles; thunder, with or without rain, is heard downtown about four days per year. But last fall’s storm was, at least on record, unprecedented--the confluence, against gigantic odds, of the necessary ingredients in exactly the right proportions at precisely the right moment in absolutely the wrong place, an act of preternatural perfection performed, perversely, in the unlikeliest venue possible. Think Maria Callas at Hooters.

From the perspective of sheer spectacle, the storm was also weather as performance art, raging with a diva’s fury at unheard-of intensities, its remarkable column of clouds and anvil top rendered as if by a plein-air painter against a pristine cerulean sky. But most amazing was its focus--rain gauges just blocks from those recording biblical deluges logged only traces. To the astonishment of meteorologists huddled around radars from Oxnard to San Diego, it scarcely moved throughout its lifespan. The storm blossomed suddenly in mid-afternoon, reached its peak just after dark, and then, with a performer’s sense of the moment--having unleashed a Wagnerian torrent of rain, hail and lightning--simply vanished from almost precisely the spot where it had formed.

For three hours the storm lashed a single square mile, and the results were calamitous: Watts, Lynwood, Willowbrook, Compton and South Gate were awash with floodwaters that lifted automobiles into front yards and piled hail into 6-foot drifts. Firefighters fished 50 or more motorists from marooned vehicles. More than 1,600 emergency calls were logged, 120 homes and six commercial structures damaged, and 45 crews dispatched to restore power knocked out by lightning. Because the storm lay directly on the approach to LAX’s four runways, 25 flights--10 of them international jumbo jets nearing the end of their fuel reserves--were diverted at the last moment to airports as far away as San Francisco.

Bill Mork, California’s state climatologist, was later flabbergasted to calculate that the storm’s peak rainfall intensity of 4.61 inches per hour qualified as a once-in-10,000-years event. (Because so much of the precipitation fell as hail, the official figures may actually underestimate the total rainfall.) “A very strange event,” Mork says. “It blew me away.”

McClung marvels that the storm formed at all. “This was basically a thunderstorm that was perfectly placed,” he says, “like a tree that forms in the only clear spot in a field and grows right up through the other trees.”

On Nov. 10, a low-pressure system spawned near the Arctic Circle began tracking southward toward the Pacific Northwest. Ordinarily these polar lows are captured by easterly trending high-speed winds--the fabled jet stream. But this system possessed enough belligerent energy to barge through the jet stream and keep right on going, finally settling into a desultory holding pattern 800 miles off the coast of Los Angeles.

Isolated hundreds of miles south of the jet stream, the storm had degraded, at least in name, into a “cutoff low”--a calf culled from the meteorological herd; cutoff lows typically meander and weaken until nudged ashore by more assertive systems. But this one arrived with an ample supply of Arctic air. “It pulled down the cold polar air with it,” McClung says, “so it maintained its energy after it got cut off. A lot of energy.”

As the low loitered off the coast--potent, compact and having bypassed the jet stream’s energy-sucking winds--it began to organize into a vertically stacked structure resembling a hurricane. “As it propagated, it moved a little bit, stopped,” McClung says, “moved a little bit, stopped.” The low was moving eastward at a glacial 10 miles per hour. The meteorologists knew that when it finally came ashore, it could create something more formidable than the wan weather produced by a typical cutoff low. What no one could foresee was that almost incalculable circumstances would conjure a storm unlikely to be seen again in Los Angeles for 10,000 years.

Robert Fovell, a professor in UCLA’s Atmospheric Sciences Department, is an expert in thunderstorm modeling. Every morning, he downloads data from the National Weather Service and plugs it into a forecasting model called the MM5. On the morning of Nov. 12, Fovell ran the model as usual. The program churned out its summary around noon, just as Fovell was walking into class. “I didn’t get a chance to see it then,” he recalls. “And it was probably better I didn’t because it would have ruined my lesson plan.”

What the MM5 had spit out was a map of the L.A. Basin showing tightly spaced, sinuous lines projecting rainfall totals as high as 3 inches. The model underestimated the precipitation by almost 50%--but it was an uncanny prophecy of the storm about to erupt.

Thunderstorms require three ingredients to form: unstable air rich in water vapor; cold temperatures aloft; and a forceful current to lift the warm, moist air into the colder air above. The cutoff low poised to come ashore on Nov. 12 provided the second of the three ingredients. Warm, moist, highly unstable air also happened to be flowing uninhibitedly into L.A. from the Gulf of California.

Unstable air--caused by surface heating, certain kinds of winds, or other factors--tends to rise. As it does, it cools at a slower rate than the stable air surrounding it. Eventually, the rising air and surrounding air reach the same temperature, the so-called level of free convection. Unstable air lifted to the level of free convection will almost always continue to rise until, if conditions are favorable, it forms a thunderstorm.

On this day, the altitude of free convection was unusually low; the moist, unstable air wouldn’t have to be lifted very much to start the engine to form a thunderstorm.

But, as Fovell notes, “air doesn’t just start rushing upwards. It needs a push.”

Several hours before the thunderstorm formed over Watts, rain began falling to the east of L.A., chilling the atmosphere and creating what Fovell, in full professorial mode, describes as a “precipitation-abetted density current”--a small-scale cold front. This was the push the air needed to rise. At 1 p.m., temperatures in cities east of L.A. plunged--evidence, Fovell theorizes, of the front’s westward march toward L.A. Here was the final ingredient.

The cold front reached the warm, unstable air lingering over L.A. just as the cutoff low finally crept ashore. Now, instead of hovering over 60-degree ocean water, the low was above land heated to 75 to 80 degrees, supercharging its lifting power. All the elements were in place: a cold, potent, upper-level low hovering like a vast chimney above a mass of unusually warm, unstable air that just been given a kick in the pants by a rogue cold front. It was about 2 p.m. Within the hour, the radar at the National Weather Service in Oxnard would light up as almost never before.

The first sign came at 2:35 p.m. on the Oxnard radar screens, a red splotch appeared over Compton--the reflection, measured in decibels, from a microwave beam sweeping the L.A. basin. The beam had encountered an area of extremely heavy precipitation strong enough to shoot back a return in the 60- to 65-decibel range, an intensity almost unheard of here. The meteorologists at Oxnard began probing the storm’s structure with Doppler radar, slicing through the core 16 times from bottom to top. “As we got higher and higher, we could see this bright spot on the radar,” McClung says. At that moment rain was barely falling--a Department of Water and Power rain gauge near Lynwood was recording only a light shower. But photos taken from a weather satellite depicted a wedge-shaped plume of clouds boiling up from the L.A. Basin. The thunderstorm was building.

The splotch on the radar depicted a dome of precipitation suspended aloft by the storm’s tremendous updrafts. Instead of falling, the raindrops were being lifted to the very top of the storm, where they froze and formed a sprawling crown of hail. Eventually, the forecasters knew, the supply of warm, moist air at the surface would be cut off, the thunderstorm’s engine of convection would sputter and the crown of ice would come crashing down. In a typical severe thunderstorm, this “core collapse” would have impressive but not catastrophic consequences; thunderstorms can travel at more than 50 miles per hour, and heavy precipitation is usually dispersed across miles.

But it was becoming apparent that this thunderstorm wasn’t moving. The massive dome of precipitation would fall not over several counties, but a handful of city blocks. The implications were appalling. At Oxnard, computers were projecting epic rainfall rates over South-Central. In satellite imagery, the hurricane-like upper-level low swirled in place while the thunderstorm boiled, stationary on the southwestern flank. At 3:42 p.m., Dave Gomberg, the lead National Weather Service forecaster on duty, typed out a flash-flood warning for southern Los Angeles County. By standard procedure, the warning was set to expire in one hour.

Steve Johnson turned onto the 405 from the Santa Monica Freeway and drove south. The Fresno businessman chases thunderstorms in his spare time, and he was stunned at what loomed through his windshield: a towering, anvil-topped cumulonimbus punching up to the stratosphere, pink and golden white from the setting sun.

“It was a monster,” Johnson says. “Just a massive wall going straight up to 40,000 feet.”

The anvil showed evidence of “backshearing”--seen in only the fiercest thunderstorms. Backshearing occurs when a thunderstorm’s updraft streams out the top of the storm with such force that it drags the cloud backward. “The anvil boils to the west, against the prevailing winds, and overhangs the rest of the tower,” he says. “It’s rare to see California storms do that.”

Johnson exited the 405 and set a course for the storm’s southwestern flank. As he headed into Watts, all he could think was: “I never dreamed in a million years I’d chase in the L.A. Basin.”

At UCLA, Fovell walked out of his seminar. “Someone came running up to me and said, ‘We’ve got a 60 dBZ echo hanging over West L.A.!’ ” This is the weather-geek equivalent of spotting J. Lo shopping at Payless shoes. Fovell, with another seminar to attend, reluctantly headed back to class while the storm his model had projected hours before continued to build.

In the hour since the flash-flood warning had been issued, the thunderstorm still hadn’t moved. The Lynwood rain gauge that had showed only sprinkles was overflowing. Still, it was expected the storm would weaken.

Instead, it got stronger. Thunderstorms associated with fast-moving fronts ordinarily wax and wane; cells on the leading edge falter as new cells form to the rear. At 4:13 p.m., the storm began showing these same symptoms--except it still wasn’t moving. An arc of bright red radar readings appeared over Gardena and Hawthorne, and for a moment the storm appeared to have clove itself in two, the radar images like a CAT scan of left- and right-brain activity. At 4:20, the halves of the storm’s brain merged. A pink stain, indicating potential rainfall totals of 2 inches per hour, spread over the radar from Inglewood to Compton. Still, the rain at the ground was a fraction of what hung, suspended, near the top of the storm. “That was going to have to come down at some point,” says the National Weather Service’s Chris Jacobson, who archived the day’s radar data. At 4:43, the flash-flood warning was extended an hour.

Michael A. Sandoval, a cameraman for ABC 7 News, approached the storm from above the 105 freeway in a helicopter piloted by reporter Scott Reiff. Through the heavy rain Reiff saw what looked like a clear path. “There was an opening,” Sandoval says, “and there were big dark clouds on both sides. Scott went right through it.”

To Sandoval, it felt as if they were flying through a tunnel. “Then this lightning started striking all around us,” he says. “It was popping, snapping, like the crack of a whip times ten. We could feel the thunder, the vibrations.”

When they had shot the gap, Reiff headed back toward the storm. In seconds, the helicopter encountered extremely heavy rain that rattled its skin like gunfire. Sandoval operates a remote-controlled camera mounted on the nose of the helicopter, and he was having difficulty finding an angle that wasn’t obscured. “There was so much rain,” he says, “it was a deluge coming across the lens.”

In the aerie of the 277-foot FAA tower at Los Angeles International Airport, Sheri McClanahan, an air-traffic controller, had watched as the storm developed directly in the path of runways 25 Left and 25 Right, the southernmost of LAX’s four parallel runways, at the “outer marker,” where pilots begin their final descent. “It’s a bad place for a thunderstorm to sit,” she says. “If you can’t get through the outer marker, you can’t run approaches.”

McClanahan continued clearing planes to the airport’s north complex, but by 4:30 p.m., the storm blocked passage to all four runways. Meanwhile, airliners converging on L.A. from around the globe were turned away: Virgin Atlantic 007 from London and China Southern 327 from Guangzhou diverted to Las Vegas; Aeroflot 321 from Moscow ended up in San Francisco; Air New Zealand 001 from Auckland went to San Diego. Air France 068 from Paris landed at Ontario International Airport, only to be prohibited from disembarking passengers because no customs officials were on duty.

By 5 p.m., McClanahan noticed an eerie quiet. “The gates were almost all empty,” she says. And still the storm refused to budge. McClanahan, who has worked at LAX for 12 years, says: “I’ve never seen one just sit there like that.”

At 5 p.m., the radar readings in Oxnard were inching up to the absolute maximums: a pale purple splotch that appeared over Compton, then Lynwood.

The torrent hitting the streets meant that the great engine of lift--the warm air that had sustained the storm--was shutting down. This did not mean the rain would stop; on the contrary, as a thunderstorm dies, it releases into the atmosphere the vast amounts of energy that created it.

As the storm collapsed, so did the dome of hail that had hovered all afternoon like a bomb. The hail itself was relatively small, between the size of a dime and a quarter, but the sheer volume--at least 2 inches accumulated on the ground, which piled into 6-foot high drifts--stunned the meteorologists. In hindsight, McClung speculates “almost all the raindrops in this storm were lifted about the level of freezing.” And now, as the storm that created them died, they plummeted.

Fovell extricated himself from the seminar at UCLA and finally got a look at the model that had predicted the formation of the storm now hammering away to the south. “Wow! Bull’s-eye!” he exclaimed. “I got it exactly!”

At 5:30 p.m., Janice Hahn -- councilwoman for L.A.’s 15th District, within whose borders the storm had capriciously formed--pulled out of the City Hall garage and drove south on the Harbor Freeway to San Pedro. The weather downtown was threatening. “You definitely knew there was a storm.”

Then, as Hahn passed Century Boulevard in Watts, her car was hammered by hail. “We were being absolutely pounded,” she says. “I couldn’t hear my radio it was so loud.” Traffic slowed to a crawl. Hahn glanced at other drivers. “Everyone was kind of like, What is this?” she says.

Then, just as suddenly, it was over. By the time Hahn arrived in San Pedro, there was nothing--no hail, no rain, not a ripple of weather. “I tried to explain this to the crowd I’m speaking to,” she says, “and they kind of looked at me like I was crazy.”

Hahn finished and moved on to another meeting. Her cellphone rang. It was her field deputy in Watts. “She said, ‘I think you’d better get over here.’ ”

As Steve Johnson approached the storm, he took its measure against the hundreds of others he’d chased. “This one I could tell was a hailer,” he says. “Hailer-type storms produce tremendous amounts of lightning, and with this one, not two seconds went by without a lightning flash.”

By now it was dark, and Johnson was transfixed “by the white column of the precipitation core. All the city lights of Watts were illuminating it, like it had Hollywood spotlights on it,” he marvels. “It was like a pure white shaft coming down from God.”

Then Johnson was enveloped by the tremendous rain and hail of the core collapse. As he crossed an intersection, a wall of water rushed over the hood of his van.

Timothy Watkins, president and CEO of the Watts Labor Community Action Committee, was in his office on South Central Avenue when the storm struck--on a day, he recalls, that had started out vaguely sunny.

“There was no indication that this thing was coming on,” Watkins says. “And when it came on, it was like all at once. It started raining harder and harder, and all of a sudden it was ice the size of marbles just coming down with thunderous force.”

Watkins and his co-workers watched as the hail buried the parking lot and pummeled Watkins’ new car, eventually piling up near the storm drains. The sudden load of water and ice was too much for the roof of the committee’s headquarters, which collapsed; the roof of a nearby building used by the agency also collapsed. “The water was literally pouring in,” Watkins says. “I think we took out about 17 wheelbarrows of ice.”

Janice Hahn stood at the corner of 112th Street and Compton Boulevard, trying to make sense of the tableau before her. “First of all, there was snow on the ground--it was the hail that had built up. It covered my shoes. Cars were every which way, and all this trash and grass stuck up under the cars and washed up on people’s sidewalks and lawns.”

When Hahn arrived, there was no emergency response, “except for one fire truck. No police, no anybody. So I get on my cellphone and the first person I called was my brother.” Mayor James Hahn listened as his little sister barked that she needed street services, police, the DWP.

In Oxnard, the radar readings from the storm were rapidly fading. At 6:12 p.m., a line of thunderstorms spun up over the Palos Verdes Peninsula, a sure sign that the storm’s inflow of fuel from the ocean had been usurped. Within minutes, these too dissipated. McClung theorizes that the storm choked on its own success; its massive crown of water and hail became so large that it finally overcame the updraft that built it.

Another factor, says Fovell, was simply that the sun had set. “It’s cooling at night, the atmosphere is becoming much less favorable for convection and it knocked the legs out from underneath this guy.”

The next day, after the photos of snowball fights amid sunshine and palm trees had circulated around the world, the damage to the community did not melt away with the hail. With the damage threshold for Federal Emergency Management Agency loans in the millions of dollars, relief was not coming for hundreds of homes and businesses that had suffered serious damage. Immediately after the storm, city officials estimated that it had caused at least $500,000 in damage. Hahn established a special fund that was managed by Los Angeles Neighborhood Housing Services, enough for $3,000 to $5,000 for some homeowners and businesses, she says.

But difficulties persist. The Watts Labor Community Action Committee continues to wrangle with its insurance carrier over repairing damage from the storm. “We pay millions into insurance every year,” Watkins says, “and then the one time we really need it, we’re having to fight every inch of the way to get what we thought was coverage for this type of disaster.”

Why the storm stalled for so long in such an unlikely place may never be completely explained. Says Johnson: “To have one sit for two hours was extraordinary and unheard of.” Adds McClung: “You could go so far to say that this one storm completely monopolized all the energy of the cutoff low. It was all feeding into that one spot, that one storm.” Fovell, who more than anyone is in a position to hazard a guess, just shrugs and laughs. “I don’t know,” he says. “I don’t know.”

For the meteorologists at Oxnard, the storm was a chance to test their skills in an unprecedented, rapidly evolving situation in a locale where extreme weather mostly exists in theory. Gomberg remains awed by “just the sheer timing of it. If it had come in three hours earlier or three hours later,” he says, “it probably wouldn’t have reached that potential.”

And while it may be 10,000 more years before Los Angeles is again the scene of a such a perfect and bravura expression of natural forces, some say we were overdue.

“It was about time,” Fovell says. “We had an interesting storm here.”