Sunday, August 2, 2015

Majestic, mysterious, monstrous

The warm Gulf Stream turns deadly when it meets Arctic cold to form the Northeast's worst winter storms.

ABOARD THE NANCY FOSTER - The waters are velvet-smooth, clear and clean, alternately deep-blue and aqua, as warm as a gentle bath. They lure a family of dolphins that romp in front of the bow, diving beneath it, playing in the ship's turbulence.

As the full moon rises, backlighting the horizon, the water transforms the moonlight into a golden mosaic. The surface responds to a gentle breeze, generating ripples that scatter the light, reunite it, scatter it again.

It is another hauntingly magnificent twilight off the North Carolina coast - a scene Paul Kocin hopes never to witness in person.

The setting is the western edge of the Gulf Stream, and Kocin, who has spent his career studying storms, knows that this region is an atmospheric minefield. This is where the mighty stream and its ever-flowing warm current conspire with the atmosphere to set off some of the most dramatic fireworks on Earth.

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  • "It's an extremely dangerous, mystifying area that has a profound effect on weather," says Kocin, who deconstructed the Gulf Stream-incited "white hurricane" of 1888, among the most famous winter storms in history. "I try to stay away from it as much as possible."

    The stream is a celebrated storm-maker, for much the same reason that it has become a focal point of global-warming research: It is a prodigious mover of heat. Only in the last generation have scientists come to appreciate its power, and it continues to surprise them.

    They now know that the Gulf Stream has been an agent provocateur in almost every important winter storm to hit what is today the Interstate 95 corridor. Among them: the historic blizzard of 1888, the 1962 Ash Wednesday storm that cut Long Beach Island into five pieces, and the record 30.7-inch snowfall in January 1996.

    Even in this enchanting setting off the North Carolina coast, the Gulf Stream leaves a trail of evidence that hints at its dangerous side. The languid air borne on the current is distinctly tropical and swollen with water vapor. The vapor is palpable to the skin - as Benjamin Franklin observed when he encountered the stream in 1726. It condenses on the cool, white deck railings of the research ship Nancy Foster. The Gulf Stream is a prodigious supplier of water vapor, the combustible ingredient that has helped fuel the monster storms.

    Ordinarily, the mighty stream acts something like the fluid in an immense heating system. Its constantly flowing waters export warmth from the sun-saturated tropics toward the solar-deprived Arctic to steady the planet's temperature.

    But occasionally, the stream turns impatient and fast-forwards the process. At least a few times every winter, it mutates into a power source for coastal storms. Those are the great air mixers that rearrange the atmosphere, yanking polar air dramatically southward and shooting tropical air northward.

    When the Gulf Stream is overrun with cold air sliding off the continent, it throws its water vapor skyward, where the vapor condenses and returns as rain and snow. The condensation releases massive amounts of heat to further incite the wildly spinning winds that rip sand off beaches and pile snow into head-high drifts. The stream can turn weak storms into strong ones, strong ones into monsters.

    "That's why they like us out here," says Jamie Velarque, captain of the Nancy Foster. From the picture windows on the bridge, on this particular night, he is watching the weather closely, listening to the weather radio, monitoring the instruments sending back readings from the surface and from 100 feet under water.

    The Nancy Foster is part of the National Oceanic and Atmospheric Administration's navy that ferries scientists on research cruises. But it has another important mission: to send back live data from the stream, where "ground truth" observations are sparse. On this particular day, for example, when satellite readings indicate a water temperature in the upper 70s, the Nancy Foster is showing 84 degrees all the way down to 300 feet.

    Early evidence suggests that the Gulf Stream could be a major player this winter. Its waters have been extraordinarily warm and close to the coast. In the view of Len Pietrafesa, a storm specialist at North Carolina State University, it is primed for mischief. During the fall, water temperatures were in the 80s - readings "we have not seen in the historic record," he says. Last week, they were still in the upper 70s off Cape Hatteras. "I expect it to be a wet winter in the Northeast," he said.

    His is only informed speculation, for the mighty stream remains a mysterious force. Meteorologists know that the Gulf Stream is a big reason why the mid-Atlantic and Northeast have some of the wildest and most varied weather on the planet. The Atlantic Ocean is an awesome storm factory, and the Gulf Stream speeds up production.

    "It's pretty fantastic in terms of its influence," Pietrafesa says. And researchers believe the stream is as vital to climate as it is to weather. Says Pietrafesa: "The system is all linked." Now, with scientists reporting significant changes in the North Atlantic, they have a new urgency to figure out exactly how all the pieces fit together.

    Just when scientists think they have found answers, however, the stream comes back at them like a rogue wave flipping a boat.

    A perfect storm

    On March 9, 1888, residents of the nation's densest population center took little note of a storm approaching the South Carolina coast.

    It was expected to affect the Washington-to-New-York corridor during the next 48 hours, but not dramatically. The U.S. Weather Bureau issued prosaic forecasts calling for some clouds and rain.

    The weather agency, which by then was taking observations and issuing daily national forecasts, was part of a dizzying era of progress. The gasoline-powered automobile, the streetcar, the dishwasher, the ballpoint pen - anything seemed possible.

    As one scientist noted: "Great disasters can be anticipated and obviated."

    Nature took exception in 1888.

    Shortly before midnight on March 11, the forecast rain changed to snow in Philadelphia.

    The winds became so strong that the 10 inches of snow that fell were whipped into 10-foot drifts. The temperature plummeted from the mid-40s to 15, with stinging winds driving wind chills well below zero. Ships were stranded as howling winds blew out tide water from the Delaware River.

    More than 100 ships sank off the mid-Atlantic coast, and 80-m.p.h. winds punished Atlantic City.

    In New York City, midday temperatures plunged from 50 degrees to 6 in less than 24 hours. The blizzard's winds knocked out power to the city's elevated rails, stopping them dead in their tracks.

    In all, 400 people died in the storm - 200 in New York City alone - making it the deadliest winter storm in U.S. history. Many froze to death.

    It was the beginning of a week that altered the way Americans think about weather and drove New Yorkers to build a subway system.

    Today, meteorologists know that the white hurricane began as a "low" - an area of lighter air that on today's TV weather maps would show up as an "L."

    As that low moved eastward, a dome of frigid air from Canada crossed the Appalachians and began to slide downhill, across the coastal plain, and into the Atlantic.

    The Gulf waters off the Carolina coast in all likelihood were a good 30 degrees warmer than the air that was about to move over them. Storms grow at frontal boundaries, where cold, heavy air forces warm air to rise - an effect that Franklin hypothesized about a century earlier. The combination of frigid air and the Gulf Stream is a potent cocktail. It can take an undistinguished low and redevelop it into something special.

    Pietrafesa and his colleagues have distilled this to a mathematical formula. Subtract the temperature over land from that of the Gulf Stream and divide by the distance between the stream and the coast. The result is a storm-potential index. In short, the colder the air and the warmer the Gulf Stream, the bigger the storm.

    That's why March storms can be especially powerful. Winter air is still patrolling the upper atmosphere, while the ocean is beginning to warm.

    It was this dangerous combination that helped set off the tremendous Ash Wednesday storm of 1962, the one that took apart the beaches from North Carolina to New England.

    And it was at work in 1888, brewing a storm that caught everyone by surprise.

    Yes, the early settlers had been blitzed by storms unlike anything they had experienced at home.

    In January 1772, the Virginia snow was so deep that Thomas Jefferson and his new bride were forced to abandon their carriage and hike eight miles to their heatless Monticello mansion. Jefferson would call it "the deepest snow we have ever seen" - piled up three feet, wrote the late weather historian David Ludlum.

    But in an age of extraordinary technological advances, the blizzard of 1888 was a humbling experience.

    The forecasts had all underestimated the ability of the Gulf Stream to blow up a storm.

    And back then, of course, scientists did not even know about the Gulf Stream's evil cousin in the sky.

    Enter the Jet Age

    Dorothy Hurd Chambers worked for the old U.S. Weather Bureau and was stationed in the Rockies during World War II. Her job was to send up weather balloons to see what was going on in the upper atmosphere. This was important work, because planes with the new jet engines were flying higher than ever, and the government had to know about the jet highways. Some thought the work was too important for women, but men were scarce during the war, and Chambers was conscripted.

    She made a startling discovery. The readings the balloons were sending back from 30,000 feet were astounding - wind speeds of 80 to 120 m.p.h.

    They had encountered the jet stream, the same powerful west-to-east wind that resisted U.S. warplanes flying to Japan, and that gushes across the continent to make mischief with the Gulf Stream.

    Jet-stream winds are powerful currents so named because the winds move swiftly and pulse mightily, like jets of water through a fire hose. As they pass over storms, they lift the air radically, the way cold winds lift smoke from a chimney. Winter-storm expert Kocin, who published a seminal study of the 1888 storm 100 years later, suspects this was a particularly potent jet, with embedded streaks of wind that were even stronger.

    That blizzard became the "white hurricane," with wild winds blowing counterclockwise around a center that was off the coast and moving north. To the east, the winds drew up warm, moist air from the Gulf Stream, fueling the cyclone with more water vapor. To the north, the east-to-west winds off the ocean threw back rain and snow. To the west, northerly winds hauled down ever more frigid air from the Great Lakes region. The stronger the storm became, the more moisture it consumed.

    It was a classic illustration of how the atmosphere and the ocean are coconspirators. When water evaporates off the ocean, it joins the atmosphere as invisible vapor and stores heat. When the vapor condenses, forced upward by cold air, the heat gets released. The more heat it releases, the stronger the storm.

    The white hurricane was a gigantic system, a prototypical nor'easter - so named for the powerful winds from the northeast that they generate - penetrating deep into the high atmosphere.

    "People just think of this 'L' on the map as some sort of object," says Louis Uccellini, director of the National Centers for Environmental Prediction.

    But a low is much more than that: "It's absolutely engaging all the surrounding air around it in a systematic way."

    Uccellini oversees an empire that includes the National Hurricane Center and the severe-storm center that issues all those tornado warnings. He looks out of place in his suit and tie, talking exuberantly and wearing the constant expression of someone who can't believe what he just heard.

    Among snow geeks, Uccellini is a legend. He collaborated with Kocin on what is considered the definitive work on mid-Atlantic-Northeast storms. He knows his nor'easters.

    What makes these storms tick? What makes them go off? Uccellini believes that meteorologists are closing in on answers, but they are still playing catch-up with nature.

    The discovery of the jet stream and how it worked was a giant step for storm research.

    During the next generation, scientists would make tremendous progress in understanding the physics of storms. Running computer models that simulated the workings of the atmosphere, they used equations to predict that a nothing storm would regroup and intensify off the coast.

    Technically, the coastal lows are called "secondary storms" because they are spawned by a low moving across land. Once they develop, they become the primary storm. Meteorologists scored a spectacular success in February 1978 in predicting that just such a tempest would become one of the biggest snow-makers in history.

    Holiday on ice

    A year later, on the Sunday of Presidents Day weekend, there was humiliating failure. The official temperature in Philadelphia fell to zero that day, something that happens only once every three years. A dusting of snow was in the forecast for that night.

    "It was supposed to be this little system," says Kocin, whose high-pitched voice is familiar to viewers of the Weather Channel, where he is the winter-weather expert. "People went to sleep, and when they woke up they wondered, 'Why can't I open the door?' "

    Washington was paralyzed by two feet of snow, and Philadelphia was buried under 14.6 inches. As the storm skidded off the Virginia coast, the Gulf Stream gave it a fresh infusion of water vapor. The tremendous contrast between the bitter-cold air, the warm ocean, and a strong jet stream shut down the I-95 corridor from Washington to Philadelphia.

    Chet Henricksen, a retired Weather Service meteorologist who was working in Washington at the time, says the Gulf Stream took a powerful storm and turned it into a winter hurricane. In satellite imagery, the storm had a well-defined eye.

    In 1980, the storm lexicon gained a new buzzword, borrowed from wartime terminology. Frederick Sanders of the Massachusetts Institute of Technology and John Gyakum of McGill University began looking at the history of rapidly developing storms all over the world. They found a class of cyclones that literally blew up, like the one in 1979. The storms intensified so quickly that they needed a classification of their own.

    The two scientists called them "bombs." In bombs, the barometric pressure falls in a hurry. Maximum winds can rapidly jump from 30 m.p.h. to 50 m.p.h., says Joseph Sinkiewicz, the Atlantic forecaster at the government's Ocean Prediction Center.

    Gyakum and Sanders found two places on Earth that were the primary breeding grounds of bombs. One was near the Kuroshio Current, off Japan, and the other was the Gulf Stream. Their paper generated a rush of research into these suddenly developing storms, and that research paid big dividends.

    By the early 1980s, meteorologists were able to feed Gulf Stream temperature data into their computer models. They scored extraordinary successes, forecasting the February 1983 blizzard that left a record amount of snow in Philadelphia, and the January 1996 snows that broke that record.

    After two centuries of painstaking scientific inquiry, the Gulf Stream was finally shedding some of its mystique.

    A sea change for forecasting

    Today, scientists are hoping that deeper understanding and computer models will lead to the ultimate forecast: What will happen to Earth's climate? How will the Gulf Stream behave in the future? Will it keep moving heat? If not, what does that mean for the future of arctic ice and sea levels all over the world?

    While they know that computer models have wrought remarkable advances in weather forecasting, climate prediction is a wholly different pursuit. And they know they have their limitations. The Gulf Stream is poorly represented in those climate models.

    In early 2000, the National Oceanic and Atmospheric Administration introduced a new supercomputer and boldly announced that the era of the "no-surprise" Weather Service was at hand.

    At dawn exactly one week later, the Gulf Stream waylaid the Weather Service and just about the entire meteorological community.

    On Jan. 24, 2000, a storm edged off the North Carolina coast. The computer models insisted that it would be a nonevent from Washington north. No Home Depot stampede, no Acme rush, no school-closing numbers. Millions of people in the Northeast Corridor went to bed undisturbed, at least from weather anxiety.

    When they woke up in the morning, blinding snows blocked the views from their windows. Up to two feet buried parts of North Carolina.

    Before the storm hit, bitingly cold air had surged toward the Gulf Stream. In 24 hours, the temperature plummeted 30 degrees in a zone from Wilmington, N.C., to Morehead City.

    The frigid mass and the ultra-warm Gulf waters created a perfect environment for the storm to blow up into a bomb.

    It did - in the very area that the Nancy Foster was monitoring a few months ago, that "dangerous, mystifying" place.


    Contact staff writer Anthony R. Wood at 610-313-8210 or twood@phillynews.com.
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