So, I made a mistake the other day. Negative phase of PNA means ridge (warmth) along East Coast, not trough (cool)! Sorry! I get my phases mixed up all the time because they are so arbitrary. For what it’s worth, I’ve posted the latest forecast, which now averages out to roughly zero, and an image of what the PNA actually looks like (so that we can avoid this silliness again), both courtesy of the Climate Prediction Center. 

fuckyeahfluiddynamics:

In this video a very viscous (but still Newtonian) fluid is falling in a stream onto a moving belt. Initially, the belt is moving quickly enough that the viscous stream creates a straight thread. As the belt is slowed, the stream begins to meander sinusoidally and ultimately begins to coil. Aside from some transient behavior when the speed of the belt is changed very quickly, the behavior of the thread is very consistent within a particular speed regime. This is indicative of a nonlinear dynamical system; each shift in behavior due to the changing speed of the belt is called a bifurcation and can be identified mathematically from the governing equation(s) of the system. (Video credit: S. Morris et al)

PNA forecast to go negative, finally! That’s a large scale predictor, but if true, it means trough in the East. That means cold air. That means winter.

I see this problem come up a lot, and I’d like to address it while it’s on my mind. People say silly things like “El Nino caused this” or “Global warming caused that”. This is nonsense.

Climate variations can be divided into low-frequency (slow) and high-frequency (fast) categories. Things like El Nino, Global warming, the North Atlantic Oscillation (NAO), etc. are low-frequency variations. Weather events, such as snowstorms, thunderstorms, hurricanes, etc. are high-frequency variations. We often refer to the low-frequency variations simply as climate and the high-frequency variations as weather. Climate and weather therefore have different time scales, by definition.

In general, it’s very difficult to prove causation between these two categories. Climate does not cause individual weather events, but rather it can make them more or less likely to happen. In a sense, climate fluctuations can “load the dice” in favor of certain weather outcomes to happen. 

During a winter, for instance, lots of weather events will occur. No single event can be directly attributed to El Nino, the NAO, global warming, etc. We can only say things like “The rain we just got was more likely because of La Nina than it would have been without a La Nina”. Don’t try to put the word “cause” in there.

Note that this also applies to global warming. Climate varies due to natural causes, as discussed above, but it can also vary due to human activity. Global warming is really just a climate variation that’s caused by humans instead of nature. You can say that global warming will make certain things more or less likely… for instance, global warming will enhance the probability of stronger hurricanes, but you can never blame any individual hurricane on global warming.

So please, never say things like “Global warming caused that storm” or “La Nina is the reason it rained last week”.

Note: I’ve lumped climate events together, but in reality they also exist on many different timescales and the separation of timescales is a bit arbitrary. Also, all modes of climate variability affect one another just as they affect weather. Don’t forget that weather affects climate just as much as climate affects weather. None of these relationships are one-way!

More warm air likely to mix into this storm and give us mostly (probably all) rain. When the Lows take this track, the counterclockwise (cyclonic) flow mixes in warm air form the south. Lame.

This seems to be as good a time as any for a quick rant about snow and global warming. Our buddies at Faux News seem to like to think that lots of snow disproves global warming.

This simply isn’t true. If anything, global warming may increase the probability of snow. In very oversimplified terms, the atmosphere can be thought of as a sponge. There’s a famous relationship called the Clausius-Clapeyron Relation that quantifies the relationship between how much water the atmosphere can hold and its temperature. The warmer the atmosphere, the more moisture it can hold. It’s really that simple. (Note that the Clausius-Clapeyron relation is not linear, it’s exponential. So changes of x degrees lead to y amount more water vapor, where y > x.)

In a warmer world, more evaporation will occur, leading to more moisture in the atmosphere. This can actually lead to more snowfall. Crazy, eh?

Don’t go blaming every snowstorm on global warming though - that would also be irresponsible. But that’s a story for another day.

Note: The atmosphere doesn’t actually “hold” water vapor, and it doesn’t actually act like a sponge. For the scientifically inclined, read this page. The analogy works to first order, but the actual process on the molecular level (involving vapor pressure - anyone remember thermodynamics?) is very different from that of a sponge. 

ilovecharts:

Homework

Happy Holidays, all! Our present to you, a list of 439 organizations supporting SOPA. What you do with this information is entirely up to you. For context, there have been suggested boycotts and contact campaigns you may find interesting.   

Holiday hugs and hand-pounds.

Did anyone notice that Nintendo is in there? It’s hard to boycott super freakin Mario

These clouds are pretty awesome. The tl;dr of how they work is pretty simple: breaking waves, just like you see on the beach. The upper levels of the atmosphere move forward faster than the lower levels, and this causes wave breaking. 

Read about them: http://www.livescience.com/17545-giant-tsunami-shape-clouds-roll-alabama-sky.html

Consider, for example, the experience of professor Richard Muller, a University of California at Berkeley physicist and self-proclaimed warming skeptic. Suspecting that climatologists weren’t up to snuff as mathematicians — physicists think that about everybody — Muller put together the Berkeley Earth Surface Temperature project (BEST), secured partial funding from fossil fuel-burning interests at the Charles G. Koch Foundation, and set about to reexamine the data.

To his credit, Muller’s analysis convinced him he’d been wrong. “Our results,” he conceded in a Wall Street Journal column, “turned out to be close to those published by prior groups. We think that means that those groups had truly been very careful in their work, despite their inability to convince some skeptics of that. They managed to avoid bias in their data selection … Global warming is real. Perhaps our results will help cool this portion of the climate debate.”

Fat chance. Alas, to some, the scientific method itself — i.e., peer review by qualified experts — smacks of conspiracy. Ignoring the math, denialists went straight to motive, denouncing Muller as a “befuddled warmist,” who’d engineered a “predetermined con.”