Cover; Weather; Scientific American Presents; by Staff Editor; 1 Page(s)

Table of Contents; Weather; Scientific American Presents; by Staff Editor; 2 Page(s)

Masthead; Weather; Scientific American Presents; by Staff Editor; 1 Page(s)

Introduction/Our National Passion; Weather; Scientific American Presents; by Davidson; 6 Page(s)

A generation ago adolescent meteorologists monitored local weather by turning milk cartons into barometers and Ping-Pong balls into anemometers. But nowadays, simply by tapping a keyboard, their successors can track weather as it happens all over the globe. The World Wide Web offers a jungle of "weather weenie" sites. Its users can stare until stupefied at weather-radar imagery from St. Louis, St. Paul or St. Cloud, satellite pictures of fog hugging the California coast or the Appalachian foothills, charts that depict dry lines and tropical maps that show a long, sinister red band. That band is the thermal signature of El Nino, now mercifully slumbering in Pacific Ocean waters (until it strikes again!). "And Hurricane Floyd probably sucked more people onto the Internet than it did palm trees and street signs into its swirling maw," joked the Los Angeles Times.

The modern fascination with weather is also epitomized by tornado chasers on the Plains, politically charged conferences on climate change and the Weather Channel on cable television. In the age of CNN and MSNBC, weather disasters receive the breathless, moment-by-moment, you-are-there coverage once reserved for wars. In the comfort of our living rooms in New York City and San Diego and Dubuque, we watch live TV images from the southeastern U.S. as Hurricane Floyd pounds beach mansions into pulp. Pundits, meanwhile, exploit every atmospheric disaster-a Chicago heat wave, a California monsoon, a Northeastern blizzard-as material for debate: Is the weather changing? Are we to blame?

The Perils of Prediction/Forecasting is No Picnic; Weather; Scientific American Presents; by Monastersky; 8 Page(s)

Last summer a gaggle of government dignitaries flocked to the end of Thunder Road, a quarter-mile-long strip of asphalt tucked behind Washington Dulles Airport. There, in the shadow of a giant radar dome, the bureaucrats celebrated the end of a nearly 20-year struggle to bring the National Weather Service (NWS) into the information age. This $4.5-billion modernization effort has furnished U.S. federal forecasters with sophisticated Doppler radar, a nationwide communications network, vastly improved computing power and a new suite of satellites.

To test-drive the revamped system, I enlisted the full force of the weather service to answer a simple question: Will it rain on an upcoming picnic planned for my son's birthday in early October? For a 10-day period before the event, I turned into a weather weenie, keeping in close contact with meteorologists drawing up the forecasts for Saturday, October 9. Aside from helping me plan the picnic, the exercise allowed the weather service to show off its advanced capabilities and to explain exactly how meteorologists go about predicting the weather.

The Perils of Prediction/Decoding the Forecast; Weather; Scientific American Presents; by Raikhel; 2 Page(s)

A glossary of common weather terms (pictures)

The Perils of Prediction/The Butterfly that Roared; Weather; Scientific American Presents; by Rosenfeld; 6 Page(s)

Weather forecasters are a frequently humbled bunch. No matter how far their science advances, the atmosphere finds ways to defy prediction. In 1998, for example, sophisticated computer models helped the National Weather Service (NWS) achieve the highest forecast accuracy in its 130-year history. But a disturbing number of meteorological events that same year proved how fragile that achievement was. Take what happened on Thursday, February 19, 1998. The models predicted a stormy weekend in Louisiana. Fortunately, though, meteorologists were flying over the Pacific Ocean for a special research mission and reported one small correction. The jet stream was moving much faster than expected far off the coast of Alaska. Rerunning the models with the new information, NWS meteorologists saw that storms would probably strike central Florida, not Louisiana.

By Sunday at 2 P.M., confident forecasters issued a tornado watch-seven hours ahead of a deadly tornado outbreak in the Orlando area. A little discrepancy in the pattern of air flowing more than 4,000 miles away had made the difference between an accurate forecast and a bust. The change in the winds in Alaska had displaced storms in the southeast by several hundreds of miles-endangering people living near Orlando, not New Orleans. Blame what happened on chaos, the way small uncertainties in atmospheric conditions in one place can produce enormous consequences at a huge distance. Chaos is the bane of weather forecasters because it adds untold complexity to the models they use to make predictions.

The Perils of Prediction/Do We Need the National Weather Service?; Weather; Scientific American Presents; by Rosenfeld; 4 Page(s)

You're getting ready for an adventure, packing up for a pleasure cruise from New England to the warmer climes of Bermuda. Next to your life vest, your charts and your provisions, what you need most is an accurate weather forecast. The forecast had better last you a good four days, close to the limit of reliable prediction.

"Most people know it's risky behavior to take a boat out into the open ocean," says Ken McKinley of Locus Weather, a one-man meteorological bureau in Camden, Me., that helps mariners reduce that risk. Every year hundreds of them plunk down about $100 for McKinley's advice before embarking on an ocean voyage, even though they can get a free five-day forecast from the National Weather Service (NWS). They prefer McKinley's customized assessments of wind shifts and wave heights to the generalized statements from the government agency. Even crusty old Yankee skippers, self-sufficient types who can make their own forecasts, will hire McKinley for a consultation.

Unsettled Skies/Billion-Dollar Twister; Weather; Scientific American Presents; by Henson; 8 Page(s)

For drama's sake, it's tempting to say there was something spooky in the air. But as dawn broke across Oklahoma on May 3 of last year, the conditions weren't especially ominous. True, it was a bit humid and breezy, but nothing special for springtime. Wheatfields near Oklahoma City were tossing in a 25-mile-per-hour wind by midafternoon, but wind is to Oklahoma as snow is to Alaska. It's part of the fabric of life and-usually-of little consequence.

Five hours later some 8,000 buildings in central Oklahoma lay in partial or total ruin. A seemingly endless swarm of tornadoes had ravaged a 150-mile-long belt running from southwest Oklahoma diagonally across the state to near Wichita, Kan. Across this swath, at least one twister was spinning on the ground at every moment from 4:45 to 10:45 P.M.-except for a two-minute lull midway through the period, as if nature were catching its breath.

Unsettled Skies/Extreme Weather; Weather; Scientific American Presents; by Raikhel; 2 Page(s)

STORMS: 1.DEADLIEST TORNADO IN THE U.S. Missouri, Illinois and Indiana On March 18, 1925, a twister cut a 219-mile path through three states, killing some 689 and injuring nearly 2,000. 2.LARGEST TORNADO OUTBREAK IN THE U.S. Ohio River Valley On April 3 and 4, 1974, a storm system spawned over 125 tornadoes from Indiana to northern Georgia, nearly a quarter of them rating as fearsome F4s or F5s.

3.DEADLIEST HURRICANE TO HIT THE U.S. Galveston, Tex. Not expected to be destructive, the 1900 storm ravaged the island with 100-mph winds and a 20-foot storm surge; an estimated 8,000 people died. 4.DEADLIEST FLOOD CAUSED BY A STORM SURGE Bangladesh (East Pakistan) In November 1970 a cyclone in the Bay of Bengal killed about 300,000 people.

Unsettled Skies/Fleeing Floyd; Weather; Scientific American Presents; by Reed; 6 Page(s)

Last September Hurricane Floyd became one of the largest tropical cyclones to form over the Atlantic Ocean. As it threatened to incapacitate several major cities along the southeastern coast of the U.S., the nation's civil defense system snapped into gear. Sirens howled, schools and courthouses closed, and navy ships headed to sea. Along barrier islands, soldiers darted among houses instructing residents to clear out, while the National Aeronautics and Space Administration battened down its shuttles.

As the 600-mile-wide storm bore down on Florida with winds of 155 miles per hour--just one mile per hour below the threshold of the fiercest, Category 5, storms-the specter of its potency chilled coastal residents and alarmed local emergency managers. "Floyd had the potential to be the worst hurricane to ever strike the East Coast," says James Lee Witt, director of the Federal Emergency Management Agency (FEMA) and a cabinet adviser to President Bill Clinton on natural disasters. "This is the first time we have ever had an evacuation that involved so many states at one time. It was my worst fear."

Unsettled Skies/Big Sky, Hot Nights, Red Sprites; Weather; Scientific American Presents; by Wright; 6 Page(s)

When speeding along the straight arrow of State Highway 14 outside Fort Collins, Colo., it's easy to miss the turnoff onto the dirt road that runs past Walt Lyons's house. From the dirt road it's easy to miss his driveway, too, which winds up a low bluff to the east. The land here is like an open palm, its contents-prairie, farms, horses and cattle-standing in plain view. Even so, roads and houses are inconspicuous, dwarfed by the sheer scale of their expansive surroundings.

On a clear, still morning in October, it's hard to imagine summers at the Lyons place, when hordes of scientists from all over the globe converge on a rooftop deck for all-night skywatching sessions. The sky they're watching stretches from North Dakota to Texas and hosts some of the largest, most energetic thunderstorms on the planet. High above those storms, split-second flashes of colored light dance in bewitching displays that have escaped the notice of trained observers for millennia. Only a decade has passed since the phenomena-a kind of cross between lightning and auroras-were discovered. Yet they may play a pivotal role in passing energy between the earth and space, helping to maintain an ethereal network known as the global electrical circuit and making gamma rays in the bargain.

Unsettled Skies/It's Raining Eels: A Compendium of Weird Weather; Weather; Scientific American Presents; by Cerveny; 2 Page(s)

May 19, 1780 DARKNESS AT NOON: A smoky blackness settled over the New England states, possibly the result of massive forest fires in Western states. It was so dark that by noon, people had to light candles and lamps to see. Even with the aid of lanterns, farmers could scarcely get to their barns to care for their livestock.

March 1876 JERKY FROM HEAVEN: Scientific American reported that many witnesses in Bath County in northeast Kentucky observed "flakes of meat" drifting down from a clear sky. One investigator declared that some of the flakes tasted like mutton or venison. The cause: Lightning may have roasted a flock of birds.

Unsettled Skies/Tempests From the Sun; Weather; Scientific American Presents; by Beardsley, side bar by Staedter; 8 Page(s)

In a sheltered Arctic valley in Greenland, a pulsing radar beam emanates from a 32-meter dish antenna. As I watch, the dish sweeps across the night sky, probing the ionosphere, a huge part of the atmosphere above 50 kilometers where atoms dissociate into electrons and ions. The antenna collects faint reflections that reveal distinct layers where electrons and ions swirl in unusual numbers.

An hour earlier the radar, located at the Sondrestrom Upper Atmospheric Research Facility, had detected prominent signals bouncing back from 140 kilometers up. They were coming from the aurora borealis, visible patches in the ionosphere where high-energy particles from space strike oxygen and nitrogen atoms. The collisions excite the atoms and cause them to emit light of different colors, producing the spectacular displays known as the northern lights. But now, as midnight approaches, the aurora has dissipated. It is a quiet night in Earth's nearspace environment.

Doing Something About It/Cloud Dancers; Weather; Scientific American Presents; by Pendick; 6 Page(s)

Water. Everybody needs it. Almost everybody who has it could use more of it. And those who don't have it would do almost anything to get it. For millennia, the traditional technology for obtaining water was simple enough-a hole in the ground. Shamans and charlatans alike also appealed to the sky to boost their water supplies. Half a century ago in a laboratory in Schenectady, N.Y., scientists came up with an entirely new version of the tribal rain dance: cloud seeding. By scattering chemical "seeds" in rain clouds, they hoped to augment natural rainfall to replenish water tables and reservoirs.

Rainfall enhancement, as its practitioners like to call it, remains just one variation of the much older dream of controlling the weather. Taming tornadoes with A-bombs, short-circuiting lightning storms with metal chaff, smothering hurricanes at sea, quashing damaging hail-all have been proposed or attempted since that fateful day in Schenectady.

Doing Something About It/Cloud Dancers; Weather; Scientific American Presents; by Pendick; 6 Page(s)

The modern commercial airliner is a symbol of sleek modernity, an emblem of our success in conquering the elements. Yet few commonplace human endeavors place people so thoroughly at the mercy of nature quite like aviation does. In fact, 26 percent of commercial airline accidents and almost 20 percent of all general aviation-small aircraft-accidents list weather as a contributing factor. Weather also helps lead to flight delays and wreaks unexpected havoc with the hub-and-spoke system, which flies travelers into a central port to change planes. A storm in Atlanta can delay flights out of San Francisco. And with air traffic scheduled to increase by nearly 50 percent over the next decade, smooth flow of flights will rely on weather and modern forecasting.

In aviation, however, an unfortunate, oft-cited aphorism preaches that it takes a major accident to spur the government to improve the system. "It's called tombstone technology," explains John McCarthy, a meteorologist at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. NCAR works with the Federal Aviation Administration (FAA), the National Weather Service (NWS), research universities and private enterprise to push aviation weather forecasting to new limits. And over the past three decades McCarthy has often been in the middle of such efforts. "We have an old maxim in the aviation weather business that weather is not a big problem until it is a big problem," he adds.

Climate in Flux/Beyond El Niño; Weather; Scientific American Presents; by Lippsett; 8 Page(s)

Long before anyone ever heard of the Pacific warming called El Nino, a guy named Joseph demonstrated the enormous value of a reliable climate forecast. His discovery wasn't published in a scientific journal but rather in a book called Genesis.

The pharoah of Egypt had a disturbing dream: seven cows, sleek and fat, emerged from the Nile River. Seven gaunt and thin cows followed and ate the fat ones. Joseph interpreted the dream, warning that Egypt would have seven years of plenty followed by seven years of famine. He urged the pharaoh to take advantage of the good years to store surplus grain. So it was done. After seven years of bumper crops throughout the region, "there was famine in all lands; but in all the land of Egypt there was bread."

Climate in Flux/Warming to Climate Change; Weather; Scientific American Presents; by Brown; 6 Page(s)

For geophysicist Gunter Weller, getting to the office is a real trip. On weekday mornings around 7 A.M., Weller gingerly backs his black Toyota SUV down the driveway and into the icy fog that shrouds Fairbanks. His car creeps, antlike, for three miles to the University of Alaska. It's not the morning darkness-or even the icy air-that puts Weller on guard. Rather it's the sudden lurches and gaping cracks that emerge from nowhere in the road-scars of the permafrost melting below the ground.

Record warm temperatures are gnawing away at the masses of ice that lie beneath Alaska and other Arctic areas-and, in the process, buckling roads, tilting trees and threatening homes. Eventually much of the boreal forests that color Alaska could dissolve into wetlands, which could, in turn, become grassland. This ecosystem makeover is a dramatic show of climate change-and perhaps a distressing harbinger of things to come. "We are beginning to see the greenhouse effect-and it's not pretty," notes Weller, director of the university's Cooperative Institute for Arctic Research.

Climate in Flux/Under the Weather; Weather; Scientific American Presents; by Baron-Faust; 7 Page(s)

The wind has different names: the poison simoom of North Africa, the bad-tempered melteme of the Aegean, the violent mezzar-ifoullousen of Morocco. Cultures throughout time have reasonably feared dangerous winds and other weather catastrophes because of the immediate effects on fortune and health: high heat can kill directly, as can rampaging floods from hurricanes or monsoons. Yet weather works less overt mischief as well, such as when it fosters the proliferation of pests that transmit infectious diseases or when it disrupts the integrity of water supplies.

The weather's power over health was demonstrated dramatically several times in the space of just a few weeks in 1999: In three states along the U.S. East Coast, weeks of drought and intense heat created ideal breeding conditions for mosquitoes that turned out to be carrying an encephalitis virus never before seen in the Western Hemisphere. Fifty-six cases were reported, with seven deaths.

Atmosphere As Spectacle/Channeling the Weather; Weather; Scientific American Presents; by Cerveny; 6 Page(s)

The easiest job in America is probably being a television weather forecaster in San Diego. If you can say the words "sunny" and "70" without ejecting your dentures, go ahead and fill out a job application. Or so you'd think. Actually, performing on television is a lot more difficult than it looks. I know. That guy in the picture is me. Fortunately for the good people of Pennsylvania, my single appearance as a TV weather guy projected no farther than the studio control booth at Pennsylvania State University.

Only about half of America's TV weather folk are certified meteorologists, a statistic that annoyed meteorologist Fred Gadomski enough for him to offer senior meteorology majors at Penn State a class on how to be on TV. "In a perfect world, everyone who told you about the weather on television should be a meteorologist," Gadomski says. "They know the most about it, and there are a few times each year when the weather gets really serious, and it can mean something to your life or your property. You don't want some Joe Schmoe handling it."

Atmosphere as Spectacle/Lights, Camera, Weather; Weather; Scientific American Presents; by Cerveny; 1 Page(s)

In much the same way that Jim Carrey's character in the 1998 film The Truman Show suffered through simulated lightning, thunder and rain, believing they were real, moviegoers often fail to realize that the weather in motion pictures is almost always fake. Movie weather-as with all aspects of a film-must be at the beck and call of directors and producers. Unfortunately, the desired storms rarely occur on schedule and usually don't film particularly well. Consequently, directors typically rely on special-effects wizards to re-create the variety of weather they need.

Celluloid weather has entertained moviegoers for more than 60 years. Indeed, the very first Academy Award for special effects honored the spectacular monsoon scenes of the 1939 movie The Rains Came. During that feature's soggy climax, an astounding 10,000 gallons of water drenched the actors every minute. If that had been real rain, the deluge would have corresponded to an incredible rate of 40 inches a day. Such massive simulated downpours are produced by pumping water from large tanks into sprinklers set high above the action; the water is then captured for reuse in additional takes.

Further Information/Weather on the Web; Weather; Scientific American Presents; by Martindale; 1 Page(s)

Our National Passion page 6 The Storm Chaser Home Page www.stormchaser.niu.edu/chaser/ chaser2.html Forecasting Is No Picnic page 12 University Corporation for Atmospheric Research www.ucar.edu/wx.html

Decoding the Forecast page 20 University of Illinois' WW2010 site: ww2010.atmos.uiuc.edu/(Gh)/guides/ maps/home.rxml The Butterfly That Roared page 22 Center for Analysis and Prediction of Storms www.caps.ou.edu/