Saturday, December 26, 2015

No White Christmas for the Northeast

Probably many see this as a blessing not a curse-I can't say I've missed the snow. But it's not so great if you're a skip resort:

"Melissa Yingling, Marketing Specialist for Blue Mountain Ski Area in Palmerton, Pennsylvania, said they are not positive when they will be fully operational, but are starting to plan on opening in phases if the weather cooperates."

"The average opening for the Blue Mountain is usually the second or third week of December, Yingling said. However, they will typically try to open as soon as possible for their guests to hit the slopes."

"We're anticipating a later start than usual this year, which is a big change from our extremely early openings the last two years, she said. "Last year's pre-Thanksgiving opening was the earliest we opened the resort since being in business."

"While some resorts are urging guests to do snow dances or ask for snow for Christmas, there will be a window of opportunity for ski resort operators to work on some trails this weekend."

"It will get cold enough for most ski resorts in the Northeast to start making snow Friday night into Sunday," AccuWeather Senior Meteorologist Alex Sosnowski said.

Ok, so most people don't run a ski lift and are happy to miss the snow. At least if you have to drive in it. But what's going on?

"If you live in America, odds are you didn't wake up to anything near a white Christmas.

"Temperature records around the U.S. were shattered on Christmas Eve, with some cities like Baltimore seeing highs up to 30 degrees Fahrenheit warmer than normal."

"So what's up? It all links back to the polar vortex, the surge of cold air that hit the U.S. several winters ago, causing temperatures to plunge far below zero."

"A band of cold air called the "Arctic Oscillation" surrounds the northern latitudes of the globe. Usually, the oscillation spins quickly and traps most of the cold air around the pole, but sometimes the band will slow and some of that cold will slip downwards, which is what happened during the polar vortex."

The opposite is happening now, and that oscillation is moving far faster, keeping all the cold air trapped north and making temperatures in parts of America warmer, according to the National Weather Service."

"The bizarre swings have obliterated long-held records, and places like Albany, New York -- usually blanketed under snow -- were warmer than Phoenix at 72 degrees. That temperature beat the old record of 57 degrees set in 1941."

Again, I'm happy to accept warmer weather and no snow. But surely there's a catch right? A downside? Is this about global warming. 

One thing that's clear: while it's great when it's warmer than it would normally be in the Winter, things would be very different in the Summer:

"Because it's December, this is just a curiosity, a story about weird weather. If these deviations from average were to happen in the summer, though, and they were to last as long as they have over as widespread an area as they have, it would be a heat wave big enough to cause a major national disaster. There would be many deaths, and most likely blackouts and other infrastructure failures."

"Sooner or later, that will happen. So it's worth understanding what is going on. What is causing this extreme weather event?"

No weather event has a unique cause and there's always a large random component in extreme weather.

"No weather event has a unique cause. Every weather event, this one included, has multiple factors that conspire to make it what it is."

"The atmosphere is always twisting and turning around, chaotically, with a mind of its own. Any truly extreme event results in large part from that effectively random behavior. For that reason, the specifics of individual extreme events are not predictable far ahead of time -- weather forecasting, which is the science of predicting this chaotic component, generally doesn't work for periods beyond a couple of weeks."

"But the climate sets the stage, pushing things in one direction or another and influencing the odds that an extreme event of a given type will occur."

"By making the whole planet warmer, human emissions of greenhouse gases increase the odds of a warm event like this one -- or its more dangerous hypothetical summer counterpart. If we define the event by specifying a fixed threshold -- some number of degrees above average for some number of days, say -- the global warming that we've already had makes that threshold more likely to be crossed."

"Or we can look at it another way: If the specific weather situation -- the configuration of the high and low pressure systems, the jet stream, and so forth -- were to have been in the the same state 200 years ago as today, it would have still been warm, but it wouldn't have been quite as warm as today.
I knew we humans were going to take some blame! El Nino may well also be a factor:"

"Besides human influence, the climate also fluctuates naturally. The most important natural fluctuation this winter is El Niño, a change in the state of both the ocean and the atmosphere in the tropical Pacific that comes every few years or so. The coming and going of El Nino events happens on a pace much faster than that of human-induced climate change, but still much slower and steadier than the day-to-day weather, so it makes sense to think of it as another factor gently nudging the weather in one direction."

"In addition to human-induced climate change, the big El Niño currently in place is very likely a significant factor in the present eastern warmth, because of the way it pushes the jet stream around. That's why a warm December was predicted well ahead of time (though not to the extreme that has happened); we knew through the fall that the El Niño would still be in place now, and what its effects on the U.S. tend to be."

"El Niño doesn't drive the bus by itself any more than global warming does. There's still a lot of wiggle room for the atmosphere to do its own thing. That's very apparent in the Pacific Northwest, where I am now. Normally an El Niño makes it dry here, but instead it's been the rainiest December in history. So the atmosphere's own variability must be important as well. Each of these factors is present, and likely playing some role in the specific event we see transpiring now."

OK so what's the punchline? Is the main factor global warming induced by humans. El Nino, or is it largely a random event?

"This warm event is still ongoing, so attribution studies haven't been done on it yet. But they will come. The science is reaching the point where we can make real scientific statements about the factors influencing individual weather events like this one, with numbers and statistical confidence intervals and multiple lines of evidence."

"So is the current eastern warmth due to human-induced climate change? How about the massive El Niño event that is currently underway in the tropical Pacific? Or is it just an extreme random fluctuation of the weather?"

"Detailed answers have to await the research to be done. But the basic, general answer, glib but likely true, is: Yes."

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