Lecture 8Outline of Last Lecture I. Weather of the Day notesII. Weather ModelsIII. Basic Types of ModelsIV. Finite Difference ModelV. Vertical GridVI. Spherical ProjectionVII. Topography RepresentationVIII. Key Prediction models for this class Outline of Current Lecture II. Weather of the day notesIII. Key Forces that Accelerate the AirIV. Force BalancesV. Pressure Gradient Acceleration FormulaVI. Friction ForcesCurrent LectureWeather of the day:Back to: http://tropic.ssec.wisc.edu/#Possibly a typhoon…There is east Pacific tropical cyclone activity also. Several have hit Baja and some affects in San Diego and strong affects in Arizona. Mostly just rain affects. Moisture inland, this is what has happened to Arizona. Different satellite view of cyclone developing by (infrared image that we can see at night) We can see a lot more of the same picture, a lot more stuff. Shows polar tops, as clouds move up high they form blue colors on the color map which suggest a colder top. The temperature of the clouds are around 245 degrees Kelvin which is about -28 degrees Celsius and somewhere -10 degrees below 0 Fahrenheit. Cloud tops when they get really high you get down to below 200, which is -70 – 80 degrees. Weak storm right now. Not considered a tropical storm yet. Atm Ocn 100 1st EditionNow we can look at forecasts of this:http://cup.aos.wisc.edu/will/HFIP/AOS page. Shows what we are doing in predictions. Predicting storms in East Pacific and the Atlantic. Deterministic forecast shows the red which is our forecast. And blue is GFDL forecast. And the green is a separate forecast. It shows we all sort of agree, until the end. Wisconsin model goes to the left. But the GFDL model goes toward Baja a little bit. Intensity we can also look it, the intensity is very low. Doesn’t even get passed tropical storm stage. We are the only ones who get it to tropical storm status; other models say it is notas intense. Another output here too. Ensemble forecast, run model again with slightly different physics. Can make approximations of physic calculations…Different initial conditions, almost the same, but a little different. Most numbers of ensemble are on here. Black line is the average. Even with the same model there is some differences. When time goes by these numbers start to converge. Effect of nonlinear chaos that makes solutions become less related to each other. Still there is a tight ensemble, tight packing of members. Forecast based on this and other models we just looked at are pretty certain it is going to go on this track. Book goes into this a little bit. Deterministic forecast: just one member like this last thing we saw, 3 different models, or 4 different models, if you look at one model run our best shot at what we think physics are at initial conditions, and that is the forecast. Given these initial conditions, this is the final result that is the deterministic forecast. Initial conditions determine final result. Could be wrong, but still deterministic forecast. Before all deterministic forecast, initial condition, find weather sometime later by integrating them. Now factors that influence this…Butterfly affect: small difference in initial condition can make a huge difference later on. Butterfly effect in South America can change New York weather in a week. Small effects work their way up.Example: Look at water in facet; water small doesn’t come out straight. Water wiggles when it comes out. Impossible to predict those wiggles? Could you predict those? Difficult thing to predict…Weather is wiggles…We can try to observe those wiggles. Someone probe the water coming out at very high resolution down to fractions of a millimeter you would get a ton of data. Can see what wiggles will look like a 10th of a second lateror 2 seconds later. If you go a short enough time and see big wiggle moving down stream of water, can observethat well you may be able to predict what wiggle will be 10th of a second from now when it moves down. Next wiggle may be effect of two wiggles into each other…Way up in pipe other things going on way before it gets to faucet. If there was a small imperfection, maybe hardly feel it, can eventually affect water coming out of pipe. Two imperfections could affect things, may interfere with each other.If you knew pipe perfectly, and knew all imperfections, could predict with initial conditions?No other things going on that we can’t predict. Other things or imperfections that can go on in water upstream. Maybe truck drove over? Maybe something happened upstream? We don’t know. So many things going on.Affect of initial condition wears off, just left trying to guess what can happen.What can you do with wiggle? With water coming out?One thing we can predict is that if we have faucet, handle at certain condition, water will fall straight down not across room.5 ft. away from faucet will not feel splash, can say with a lot of certainty. Can define envelope wiggles allowed to occur. Will contain all the possible places where wiggle will be.Forecast after time will deteriorate, define cylinder where wiggles will be. This is what happens with tropical cyclone. Know it starts here, it could change later.Could go different way later, can define region where solutions most likely to exist. Maybe something like 99% probability that tropical cyclone within certain region, that is what we can do with these model runs. Definitelysometime later this is the forecast. That is a deterministic prediction.Ensemble: the many lines describing different statistical forecasts we have predicted. The lines are different colors. The black line is the average between all of them. Many things can happen even within constraints of what we have observed. We know tropical cyclone isn’t going to be random, be within ensemble.Define probability of feeling tropical cyclone, someone hit, according to where you are according to ensemble. Probability low if you are way far away from ensemble.If you are in the region of ensemble, maybe 50% or 20% that tropical cyclone is going to hit you here. Most members up, but some low, so not impossible for tropical cyclone to go lower by one line. About 20% changetropical cyclone will be. If right on black line, chances of direct hit from tropical cyclone are as much as 60-70-80 %. Not 100% other solutions can happen with initial conditions. More that goes into it, looking at all models and many ensembles tropical condition centers may work