Sunday, December 10, 2006

The Worst Weather in the World

This article appears in the January issue of the North Star Monthly, a paper published in Danville, VT. The editor is Terry Hoffer, father of one of my croomates at Mizpah this fall...

“STOP. The area ahead has the worst weather in America. Many have died there from the exposure—even in the summer. Turn back now if the weather is bad.”

So read the signs on the edge of the alpine zone in New Hampshire’s White Mountains. Posted by the US Forest Service, the warning seems exaggerated on a warm summer day. But Mt. Washington’s fame as host of “the worst weather in the world” is warranted. The record of fatalities on its flanks is grim—135 since 1894, and of those, 59 expired during the months June-September. What makes Mt. Washington’s weather so deadly

Since 1932, the Mt. Washington Observatory has explored this question by monitoring the weather and conducting research atop its lonely perch at 6,288 feet. In the words of Scott Henley, the Executive Director of the Observatory, the place attracts “a certain kind of person… avid outdoorsmen and women. It’s a grueling job because you’re marooned up there.” The staff on Washington includes day and night observers who switch off on 12 hour long shifts, an intern, and the occasional visiting scientist.

I talked to Jon Cotton, the night Observer, late one night after he finished one of his hourly forays to check the instruments. Most of the measurements must be taken manually because the weather tends to disrupt electronics.

Cotton, 26, has been working at the Observatory in various capacities since 2003. A native of New Hampshire, he worked seven seasons as a hutman for the Appalachian Mountain Club and found that the Observatory, in addition to allowing him to pursue his twin passions for computer science and the outdoors, filled out his seasonal schedule.

Cotton identifies three main hazards that Observers look out for when going outside to monitor their instruments. Lightning, extreme winds, and severe white out conditions are all excellent grounds for staying indoors. “You get used to what you can take,” he says, and adds that as the staff knows exactly where to find their instruments and do not have to walk far, getting lost in a whiteout is usually not a problem.

Many visitors to Mt. Washington have not been so astute. In October, 1855, only one month after Lizzie Bourne famously expired a mere stone’s throw from the Tip-Top House, a summit hotel, Dr. Benjamin Ball, nearly shared the same fate.

Despite encountering bad weather and warnings at the Camp House, a way station along the Carriage Road, Ball recklessly coveted the summit. He had neither a guidebook nor experience hiking in the White Mountains, but he did carry a conspicuous umbrella.

Though he reached the crag that now bears his name, only a half-mile from the summit, Ball was repulsed by furious weather and retreated below treeline to spend a first night. He was no luckier in the morning—caught in unrelenting snow and clouds, he wandered all day across the alpine tundra until nightfall, when he again took refuge under the umbrella. Only on the third day did he run into a search party, allowing Ball to avoid succumbing to hypothermia.

The elements are not responsible for all the deaths on Washington. Accessible by car and train, 25 people have died in vehicular accidents. The causes have ranged from an out-of-control railcar to plane crashes and drunk driving—of the 1880 variety, involving a horse and carriage. Indeed, when the mountain’s cog railway was first built, its workers used to descend into the valley on slideboards at fabulous speeds. Only after four men died from sailing off into the rocks was the practice forbidden.

19 people have died on Washington from natural causes. The hordes of visitors to the summit make it inevitable that some deaths occur.

Hypothermia, falling ice, avalanches, falls, and drowning have killed the rest. The climate of the Presidential Range, of which Mt. Washington is the most prominent summit, is uniquely harsh. Treeline, the point at which trees are replaced by grass and shrubs, is the lowest in the world for its latitude. The ground record for wind speed, 231 mph, occurred on Mt. Washington in April, 1934.

Mountains change weather in three ways. They increase wind and precipitation and decrease temperature.

The prevailing wind around Mt. Washington is from the west. When it hits the Presidentials, the mountains force it to rise. Since gravity tugs on air molecules blown by the wind, they stay as close to the ground as possible when they pass over the top of ridge. This creates a funneling effect: with so much air passing through a small space, the wind picks up to create space for new arrivals.

Cotton compares the phenomenon to putting your thumb over a garden hose. As you constrict the flow of water, its speed rises where it can still exit the hose.

At the Observatory, average wind speed is 35 mph, and during the winter, the wind blows above 75 mph every other day on average. At Pinkham Notch, in contrast, about 4000 feet below at the eastern base of the mountain, the average wind is 4 mph.

Pinkham tends to be considerably warmer than the Observatory, too. In the atmosphere, as elevation increases, air pressure eases because there are fewer air molecules pressing down on those below. Molecules therefore expand and cool, which is why temperature usually decreases 3-5 degrees for every 1000 feet of elevation gained. In the winter, the jet stream moves south, bringing a blast of arctic air down with it. The average temperature at the Observatory is 26 degrees—meaning that for most of the year at the summit, precipitation forms as snow rather than rain.

On average, the mountain gets about 21 feet of snow per year. The strong west wind blows most of it off the high ridges and into the ravines on the east side of the mountain, thus making Tuckerman Ravine the premiere location for backcountry skiing in the northeast.

The Observatory staff works two week rotations, with eight days on and six off. Being outdoorsy group, they are often out and about on the mountainside. Neil Lareau, a day Observer, was spotted carving telemark turns down the auto road after the first snowfall in October.

In all, Washington gets a yearly average of 86 inches of “liquid equivalent”—that is, rain and snow after it has been melted. Coastal New England, in contrast, only receives about 40 inches per year.

This regional variation happens because air cools as it passes up and over the high ridges and thereby loses its ability to retain moisture. Water vapor visibly condenses and accretes into clouds—it is no coincidence that mountains tend to be wreathed in mist. Mt. Washington, for instance, is in the clouds 60% of the time. Eventually, if the temperature cools to the dew point, water vapor condenses into rain—or, if the dew point is below 32 degrees, snow.

Sometimes it is so cold that fog freezes directly onto buildings and plants, creating rime ice. While it has a delicate feathery appearance, rime ice damages trees in the alpine zone by freezing onto windward branches, thus allowing the wind to tear them off the trunk. The trees, if they survive, end up looking like flags or broomsticks, which is how botanists refer to them.

You can usually tell how high snow cover is above treeline by observing how tall plants grow. Anything that sticks out above the snow will succumb to rime ice and wind, so plants adapt by growing out instead of up.

All of these phenomena influence mountains across the globe, but the weather in the Presidentials is particularly potent due to its geography.

Anyone who has spent much time living in northern New England will notice that spells of good and bad weather tend to be brief—usually only a couple of days. This is because the prevailing west winds send alternating high and low pressure systems through the region.

High pressure systems are broad domes of air that can stretch over several states. They generally bring clear skies and cold temperatures. Most air is in the middle, and because air is always trying to equalize pressure, winds blow out from the center and spin clockwise around it.

Low pressure systems, on the other hand, are elongated and form between high pressure systems. They circulate in a counterclockwise direction, and as air blows into the center from high pressure systems, it eventually rises up to make space for molecules behind it. As water vapor gains altitude and cools, it condenses into rain, so low pressure systems tend to be wet.

In New England, low pressure systems bring in cold northern air due to their counterclockwise movement. Following on their tail, high pressure systems, rotating clockwise, reinforce the northern chill. The ensuing blast of arctic air into New England is sometimes called “the Polar Express” and explains why the region is so cool.

Indeed, the northeast is a magnet for low pressure systems. Of the 12 major storm tracks crossing the country, 9 of them exit via New England, and three converge above the Presidentials, which form a massive barrier to their progress.

“We’re the tailpipe of the United States,” says Cotton. He uses the nautical concept of fetch—the length of an area generating wind—to explain the violent gales on Washington. In a sailboat close to land, trees block the wind, making fetch negligible and sailing dull. If you move the sailboat out to the middle of the ocean, however, fetch will be much higher, sending the sailboat along much faster.

West of Mt. Washington, the next big impediment to wind is the Rocky Mountains. Gales have the entire distance across the Plains and Midwest to intensify before bursting over the ridge of the Presidentials.

Thus the area receives a furious infusion of strong winds, cold air, and moisture, making hurricane-force winds possible at any time of year and giving the area a precipitation profile to rival that of the Olympic Peninsula—except that Mt. Washington gets much more snow.

It is not surprising, then, that some American alpinists prepare for the Himalayas by climbing in the Presidentials, or that several former staff members at the Observatory have gone on to work at research stations at the South Pole. The severity of the storms and the quickness with which they spring up make it essential for any visitor, whether prepared for a blizzard or simply a summer jaunt to Lakes of the Clouds Hut, to be fully aware of the potential for danger on the mountain and have an escape plan in case dirty weather should roll in.

1 comment:

Luke said...

I enjoyed the post, it sounds like you might enjoy my job. I'll be modeling California's air, and I hope to move on to other places in the future.