| La Niña is here and bringing snow
By
Jack Kintner
According to Amar Andalkar, a Seattle physicist who is an avid ski mountaineer and author of the comprehensive website skimountaineer. com, “La Niña is here! The 2007-2008 season brings the strongest La Niña conditions in the Pacific Ocean since 1999-2000, which usually means much-above-normal snowfall for the Cascades.”
At Mt. Baker, this will probably mean abundant snowfall, as Andalkar’s comparison of snowfall records and the presence of a La Niña indicate that the North Cascades can expect anywhere from 10 to 30 percent more snow than normal during such an event.
Mt. Baker set a world record for snowfall in the La Niña year 1998-99 with 1,140 inches, just one of the three world snowfall records set at the ski area that season, the other two being for snowfall in monthly and four-month periods. This season’s outlook is a bit rosier than recent years since we have one of the stronger La Niña’s in recent history forming off the Peruvian coast.
The record set at Mt. Baker is meaningful because it’s recognized by climate professionals around the world. It wasn’t just ski area director Duncan Howat running out every so often with a tape. As the National Oceanographic and Atmospheric Administration (NOAA) citation reads, “The figure was scrutinized by the National Climate Extremes Committee, which is responsible for evaluating potential national record-setting extreme events. The committee, composed of experts from NOAA, the American Association of State Climatologists, and a regional expert from the Western Regional Climate Center, made a unanimous recommendation to the director of NOAA’s National Climatic Data Center to accept the figure.”
The previous U.S. seasonal snowfall record was 1,122 inches, set during the 1971-1972 snowfall season at Mt. Rainer/Paradise, a station located at 5,500 feet on the slopes of Mt. Rainer, about 150 miles south of Mt. Baker. The Mt. Baker Ski Area, as we know, has a base elevation of 4,200 feet and is located nine miles northeast of Baker’s summit. The record is for the annual snowfall season for the period from July 1, 1998, through June 30, 1999.
Why does this happen? El Niño – the little boy in Spanish – refers to a periodic global weather phenomenon whose effects have historically occurred during the Christmas season, which is why 16th century Peruvian fishermen first gave it the name. What they experienced was a lack of fish in their accustomed fishing grounds in the eastern Pacific, but as scientists have delved deeper into the causes of the phenomenon they have found that it all begins with a patch of water that’s just a few degrees warmer than normal that gets stuck in the eastern Pacific. When the reverse happens, when the water is colder than normal in the eastern Pacific, it’s called a La Niña, the reverse of an El Niño.
Recent discoveries have added more information. Early in the 20th century British scientist Sir Gilbert Walker noted that when the atmospheric pressure is high in Australia it’s low in Tahiti, and vice-versa. Though he didn’t understand the ramifications, he called this the Southern Oscillation.
Fifty years later, Cal Berkeley meteorologist Jacob Bjerknes discovered a connection between warm ocean temperatures and the low atmospheric pressure that accompanies heavy rainfall. That led to discovering the connection between El Niño and the Southern Oscillations, so what most people refer to as El Niño is known to scientists as El Niño-Southern Oscillation, or ENSO, and that’s how you’ll find it on the many websites that deal with the topic.
The difference in temperature isn’t great, just a few degrees, making the ENSO phenomenon into a kind of butterfly effect, a seemingly small anomaly that may go undetected for a long time but which ends up causing a huge difference in a large and chaotic system.
The term itself has an interesting history, and according to Wikipedia first appeared in a 1952 short story by Ray Bradbury (A Sound of Thunder) about time travel, although the term “butterfly effect” itself is related to the work of Edward Lorenz. In 1961, Lorenz was using a numerical computer model to rerun a weather prediction when, as a shortcut on a number in the sequence, he entered the decimal .506 instead of entering the full .506127 the computer would hold. The result was a completely different weather scenario. Lorenz published his findings in a 1963 paper for the New York Academy of Sciences which noted that, “One meteorologist remarked that if the theory were correct, one flap of a seagull’s wings could change the course of weather forever.” Later speeches and papers by Lorenz used the more poetic butterfly. According to Lorenz, upon failing to provide a title for a talk he was to present at the 139th meeting of the American Association for the Advancement of Science in 1972, Philip Merilees concocted “Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas” as a title.
So how does this affect our weather? First of all, the butterfly in this case, that patch of the Pacific Ocean that’s just a few degrees warmer or colder than normal, is huge, the size of a small continent. Normally this area of warm water gets moved westward during the northern hemisphere’s winter from the coast of South America by the trade winds where its heat and humidity produce rainy weather in the form of thunderstorms for Australia and Indonesia.
But sometimes the trade winds weaken and the warm water stays in the eastern Pacific near Peru and Ecuador. The water heats the air above it, spawning massive thunderstorms that pump huge amounts of moisture high into the atmosphere, redirecting the flow of jet stream winds. And those changes – the relocation of Earth’s heaviest rainfall from the western Pacific to the eastern Pacific and the disruption of the jet stream winds – can change world weather patterns.
It also affects the upwelling of nutrients for birds and other predators in the eastern Pacific, leading to depressed returns and, in some cases, some animals starve when their normal cycle is disrupted.
So what does all this mean for the kind of year we’ll have? Wait and see, but all indications are that there will be plenty of snow. Though Baker opened a little later than usual this year on November 29, opening day was beautiful and was followed by snowfall that came right down to sea level in Whatcom County, unusual for early December. But on the hill, said Andress, “It was perfect, and except for a few bare spots it was almost like a mid-season day, with bright sun and crunchy, cold-weather snow. For a guy who has to ski in everything from fog to rain to blinding sleet, it was a nice way to start the season.”
Of course, as can happen in fickle northwest weather, a Pineapple Express brought warm southern rains into the area and three days after such a nice opening rain wiped out 17 inches of base in 24 hours.
For a yearly comparison of snow depth and a discussion of the effects ENSO has on snowfall, go to Andakar’s website: www.skimountaineer.com/CascadeSki/CascadeSnow.html. |
