Something I've been wondering about hurricane tracking maps is if the various weather services are working together with essentially the same information and everyone wants to predict the path of the storm as accurately as possible, how is it that the models don't agree? What's the difference between them that they can take the same variables and come up with different results. Why even have competing models?
In other words, why so spaghetti?
As you might have guessed, part of the answer is that my question is itself not really correct. The most complete (and mostly over my head, technically) answer I found was in the National Hurricane Center's Technical Summary of the National Hurricane Center Track and Intensity Models (pdf).
First, they don't all use the same variables, mostly because all variables are not created equal and some data takes longer to gather and process and while that's happening it's possible to do some predicting with the data that already exists. And that means that the various models aren't competing with each other, they're complementing each other.
That said, here's my layman's view of hurricane models as described in the NHC paper.
The models are designed to evaluate the track of the storm or the intensity of the storm, or some combination of the two. They are furthermore categorized as being either early or late. Early models are based on simpler calculations so they are produced more quickly. Late models come later because the complexity of their calculations require much longer to process. When you see a guy like meteorologist Bill Karins on MSNBC excitedly announcing new models, that's in part because he's been waiting for them to process and knows that they may be more comprehensive. Some of these models come out only two or four times a day.
By the way, the words they use for the accuracy of these models is "skillful" and "unskillful." Often there is a trade-off between skillfulness and speed.
The two main categories of models are again based on the differences in the data they employ. Dynamical, or numerical models make use of the kinds of physical data that comes from radars and weather stations. Statistical models instead draw upon history and experience with past hurricanes and other weather patterns to guess at how the current storm will behave. And then some models represent a mix, perhaps with some data weighted more heavily than others, like a weather mutual fund.
Some models have specialties, like assessing the impact of interaction with land, or being espeically skillful in the short term versus the long term forecast.
There's also something called a trajectory model, which sounds to me like a "go with the flow" model, extending the path drawn by more data intensive models.
The models themselves aren't named "statistical" and "dynamical." Instead they have names like the Geophysical Fluid Dynamics Laboratory model, marked on a spaghetti graph as GFDL. The one the National Hurricane Center emphasizes is their own official forecast, marked with OFCL. I'm guessing that's why it's more distinct as the only black on in the list on the right.
Naturally, if you have any expertise in this material I greatly appreciate you sharing your insights.
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Wine may be the answer. Wine goes well with spaghetti.
We've come a long way since we relied on "the glass"( a primitive barometer, literally a glass with a liquid that rose and fell with atmospheric pressure) for weather prognostication.
And that was a giant leap for mankind, over grandma's rheumatiz. . .
Hey I still like watching the glass.
Me too. I still have use a water barometer, and a water thermometer as well. Both Torricelli and Galileo would be pleased.
My thoughts & prayers are for all on the East Coast who are rendered in harm's way. May they be safe.
Three have already been killed including a small boy in N.C
Correction: Four have died -- the last one announced by MSNBC was an 11 year-old boy who was struck by a tree that crashed into his apartment in Newport News, VA. His mom was fortunate to dodge out of the way just in time. I am sorry for her loss.
Each model has to start with a basic set of assumptions and these can vary depending on the variables you choose. Fairly accurate equations can be developed to describe a hurricane, but it may not be directly solvable without making a few assumptions to get you started. Some may require additional assumptions at a later step of the calculations. Some data is more heavily weighted than others. Make sense? This is higher order calculus, numerical analysis and possibly some finite element analysis going on here...and must be done by a computer.
Some older models were based on more simplistic forms because the computing power was more limited, but they are still relevant predictors. The earliest forms could be done without a computer. Even still, trying to build a model on all the variables will create such a complex calculation that it is not practical to run...even with modern computers, this can take too long. Plus you can have parameters that have the effect of canceling one another in the calculations, thereby rendering an inaccurate prediction. All the variations is why they also do a track that is essentially an average of all the models.
There are probably a few thousand people who have received their doctorate in the process of developing the models...theoretical and the computer programs.
Hope this helps a bit. You essentially have the right idea.
I imagine it's because each predictor uses their own algorithm, probably with quirks added by their predictor. You can usually tell where it's going by where the lines cluster together. Here in NOLA, everyone's an amateur meteorologist! And a comedian! But, nevermind that. Looking at this map, I see one taking it to the coast of France. One would hope not. Otherwise, I got nothing for ya.
ooops - sorry.. see below...
I think that one model has some passive aggression issues with France.
Those are some wild tracks !!
Hurricanes in Greenland ?? Really ?? When's the last time that happened ??
Forget all those reporters in the Caribbean doing storm stories... I wanna see some reporters up in Greenland reporting when it hits there.
BTW - what does all this rain hitting Greenland do to glacial melting there? Does it help or hurt ??
I am amused by the track to France - "BAMS".
my favorite for what you can include or not include, the Weather Underground's 'wundermap': - Includes hurricane tracking,spaghetti forecasts, local storm cell tracks (really good),lightning (really good), radar of precipitaton, run in 'map'mode (so you can see roads, counties, cities, streets),and zoom in/out with complete flexibility. Weather Undergroundit turns out is a bunch of local Florida weather interested folks thatget their weather info from everywhere, including a networkof volunteer weather stations. So you can zoom in and putEast Main and 28 Woodland Dr right where you want it. ;-)
http://www.wunderground.com/wundermap
(Be sure to try all the buttons. Definitely recommend forIrene to include radar, satellite, storm tracks.)
The year of unfiltered, in-your-face consequences of man-made climate change continues for the United States. There have been record temperatures coupled with flooding rains for some regions and unprecedented drought for others. Now a major, unprecedented hurricane slamming huge populated areas of the East Coast. This is a direct connection to the inexorable warming of our planet that has exploded in the last decade. We must do something now to stave off even worse impacts to come...
http://www.sunstateactivist.org
or could it be? Nah, that's crazy, sure it's only a coincidence. Didn't New York just legalize.....
mattpfl,
This is not a "major" hurricane. By definition, a "major hurricane" is a category 3 or higher. It is also not "unprecedented". Google past hurricane tracks since 1851 (also available from the NHC and other sources). Unprecedented means it has never happened before, and none of the events that you mentioned is "unprecedented."
My guess as to what Pat Robertson would say is.. "The Lord is still deciding whether to punish us Americans for all our sins or those Godless Canadians."
Meanwhile, in TeaPartystan: Don't be fooled by these weather "scientists", alarmists and the liberal media. It's all a hoax. "I do believe that the issue of hurricanes has been politicized," Texas Governor Rick Perry answered, according to the National Journal. "I think there are a substantial number of scientists who have manipulated data so that they will have dollars rolling into their projects."
Wouldn't need to fake it anymore, though ~ huh.
Cause "RUUUUUUNNNN !!!! ITS HITTING NEW YORK"
The dollars ought'a POUR in now !!!!!
Why is there no noodle for prayer-inspired prognostication for the Republicans to use?
I saw one map stating Chicago would be hit. Does that mean it will split and avoid southern Ontario?
A nit to pick, an observation, and a serious philosophical and scientific point:
I know a shorter word for 'skillfulness'; it's 'skill'. The difference eludes me.
Nothing says 'groundless projection' like screwing with the French during grape harvest time. I schadenfreudige love it.
Finally and seriously, the fact is that even if we had the model for hurricanes, the complexity of the model would make certainty unattainable. Nothing has harmed the understanding of complexity theory as much as the name 'Chaos Theory' or oversimplified examples such as the butterfly effect. There are innumerable simple examples of feedback loops causing chaotic behavior, some of which require no mathematical sophistication at all. These need to be a part of the national curriculum but, alas, we are still fighting about evolution.
It's not in this case that there is not a truth to be had (as in particle physics), nor that attempting to find the truth changes the truth (as with Heissenberg's famous result). Rather it is that no finite amount of knowledge, even with perfect theory or models, can bridge the gap between theory and reality. Star-planet systems with more than three or four planets are barely within our grasp, and these are basically, dead-on Newtonian systems. The gravitational interaction between the bodies is what characterizes this as a feedback or complexity problem.
We have all seen the wonderful fractal art that has been created through mathematical feedback. The best metaphor for the epistemic situation we are in with modelling complex systems such as the Earth's weather might use these. One of the alluring phenomena of these space-filling curves is symmetry of scale. You see the same patterns emerge again and again, whether you are looking at the curve at full scale, or 100x or 100,000x, whether youare looking at the center of the curve or out on an edge.
The weather models and space-filling curves are alike in that both generate outcomes or maps. Now do not think of lines on a geographical map here, think of multi-dimensional curves describing all the possible hurricanes the Earth can ever encounter with as many different axes as there are relevant variables. Mathematically, that is what these weather models do.
Prognostication amounts to looking for the best fit in those maps with the finite data we have at our disposal. Think of your weather man with a transparency having all the available information graphically represented on it sliding it across a universe-sized curve looking for the same data shape. However, and this is the critical however, there are infinitely many areas on the curve that will fit any finite set of data equally well. Now locally there may be no great difference in the behavior of the curve, but as we move along any one axis at greater distances, the curve can change drastically. In our metaphor, one of those axes is time. Moving along any axis in a fractal curve in two different but locally similar areas can change the view, the outcome, considerably.
So it is that even with the correct model of Earth's weather, we would be in a similar epistemic-scientific circumstance. When we try to project along the time axis, certainty as to where exactly we are on the curve, and thus what tomorrow might bring is absolutely unavoidable.
Please change that last 'unavoidable' to 'unattainable', which of course changes the meaning of the sentence a bit. Imagine my face a deep crimson. One just can't proof one's own writing. Not this one anyway.
Read about Edward Lorenz' work on Sensitive Dependence on Initial Conditions. He was the meteorologist who developed what we call the "Butterfly Effect" (AKA "Chaos Theory"). His work explains why the computer models do and will always vary with regard to storm prediction. There is an excellent telling of his story in layman terminology in THE SEEDS WE SOW, KINDNESS THAT FED A HUNGRY WORLD.
http://www.amazon.com/Seeds-Kindness-That-Hungry-World/dp/0865347883/ref=ntt_at_ep_dpt_1
I would submit that the best and most relevant layman's book is James Gleick's Chaos.
As other posters have said, the different tracks are based on different codes (*), different data, and have different goals. But it's not a bad rule of thumb to say that the spread of lines tells you something about our uncertainty in where the hurricane will end up. Just like a proper weather forecast for geeks would give the predicted temperatures as (say) 24+-3, meaning probably between 21 and 27. You'd see that the size of the uncertainty increased substantially as you looked further into the future, becoming almost useless after about three days. Instead, the weather forecasts give you plain numbers out to seven days, with no indication of how much the forecasters trust them. So when different (competent) people get different results, the range of possibilities tells you something about how sure we can be about the answer.
(*) The usage of the word "code" is different in the scientific programming world than it is in general programming; a scientific programmer will talk about "a code" and mean a program, while a general programmer will talk about "some code" (grammatically like "some sand"). Don't even get me started on whether "data" is plural or like "sand".
"Data" is a plural form of "datum".
I do know that its origin is datum/data, yes. But when you have it by the terabyte, it becomes awfully hard to point to an individual datum - is each bit a datum? each byte? each record? So I, and I think many other programmers, use "data" as a mass noun instead. Think of it this way: would you say "how many data are there on your hard drive" or "how much data is there on your hard drive"?
Some searching online makes it seem like both usages are standard.
Eight years of Latin study compel me to stick with the standard of "data" being the plural form of "datum".
Actually, I think the models agree surprisingly well! Just about everything has some statistical variability - some things occur more uniformly than others. A sharpshooter with a rifle can group several shots very close to a bull's eye. Weather has much more variablility. Most of the hurricane tracks lie within one storm's width of one another. That, if I'm not mistaken, is a HUGE improvement over what was possible a decade or two ago!
Looks like Hurricane Irene will turn into Tropical Storm Irene in a day or two.
Its a good thing they called Tamron in to handle this tropical storm.
Do you folks not see what is going on?
We are still afraid of everything. It comes down to the point we are afraid of Tropical Storms. The media keeps us scared. Stock market = I'm afraid. Tropical storm = I'm afraid. Future for my kids = I'm afraid. Debts and deficits = I'm afraid. Therefore, Obama = I'm afraid.
No one can convince me the media is not in bed with the GOP and Tea Party.
Any math majors out there? f(x) = scared^3. The input is proportional to the output. The more they input "scared" the more "scared" you will be.
The GOP and Tea Party have licked you suckers like a lolipop. They have you so afraid of your own shadow that it has become sickening to me. Here is their motto.
Everything and everyone wants to do you harm. And guess what, its all Obama's fault.
Quit being scared all the time! None of us live forever. However, all of us must live in the here and now.
Actually I am a math major (master's degree in fact). Your example is not a proportionality relationship, though it is at least increasing (to the extent that it means anything at all). Your conspiracy theory I find doubtful (not that I have any special expertise there). While I agree that we fear far too many things and there is an industry that encourages us to be afraid, I think you underestimate the potential danger of Irene (which had already killed four people, last I heard).
The fact that something didn't turn out as bad as we were worried it would does not necessarily mean we were wrong to worry. If a black-hatted gunslinger puts one bullet in his six-shooter and gives it a spin then points it at your head, you should worry. If he pulls the trigger and you don't die, that doesn't mean you shouldn't worry when he cocks the hammer again.
What worried me about Irene was that I've been hearing for years that the US has been letting its infrastructure crumble, and crumbling infrastructure is why Katrina so nearly destroyed New Orleans. How will New York's infrastructure handle Irene?
Scared * Scared = Scared^2 right? Scared*Scared*Scared = Scared^3 right? So forth and so on right?
Scared * Not Scared = Scared(Not Scared) right? Scared(Not Scared - Not Scared) = ScaredNotScared - Scared(Not Scared) right?
Tell me, if the input is always Scared then what exactly is the output?
Put it like this....
(Stock Market Crash*Hurricane Irene) = (Stock Market Crash*Hurricane Irene) right? We have to find the common denominator right? The common denominator is (Stock Market Crash*Hurricane Irene) right?
This denominator is not a pretty picture.
What happens if (Stock Market Crash * Bunny Rabbits Frolicking?)
I suspect you won't be as Scared.
Hardly that the media is helping the GOP & TP. More likely that they are playing to the big govt. will protect you.
lim time -> ∞ scariness(time) == 0
The "big media" isn't in bed with anyone other than their corporate stockholders. They decide what stories to put on and how to present them using this equation:
stories that scare people = higher ratings = higher profits
That's why EVERY story is about how the GOP/DCCC/Irene/Stockmarket/War/Salmonella/whatever is going to ruin your life, your health, the environment, the country.
The oil sands in Canada being processed = OH MY GOD, IT'S THE END OF THE WORLD.
Debt ceiling (increase) = OH NO! THIS WILL DESTROY THE COUNTRY
Debt ceiling (no increase) = EEK! THOSE PEOPLE WANT TO DESTROY THE COUNTRY
Medicare Reform = LITTLE OLD LADIES AND ORPHANS WILL DIE!
All "sides" of the media do it, and it works, so they keep doing it.
Here's a little Lena Horn to lighten the mood....http://www.youtube.com/watch?v=QCG3kJtQBKo&feature=player_embedded#! My layman's view of the hurricane model.... ;)
Scared + Scared = 2Scared
Scared + -2Scared = -1Scared
In other words, I'm not as Scared as absolute Scared.
There is no mathematical way for anyone to tell me the inputs don't equal the outputs.
LOL!!! I love math.
infinity to <0 = negative polls
0 = neutral polls
>0 to infinity = positive polls
f(-1)
f(0)
f(1)
The more <0 inputs will produce an output that approaches zero from the left.
IE...two negative Rantings plus one positive Ranting equals -1Ranting. That 1 ranting will be approaching zero from the left. Zero is absolute hatred of Obama.
i love love love that you referenced gilbert and sullivan in this title!