Transcription
So enjoy this quote, and uh, it's it's uh written by a fairly popular guy, as far as all of us are concerned. And uh, we'll just go ahead and start off with that, which is kind of nice. I mean, we've already talked about temperatures; uh, we've talked about pressures last week, and uh, go ahead and continue on with that. So today we're going to be talking about wind. The nice thing is is since we started off with pressure last week, um, when we get into wind, that's pressure has everything to do with wind, so we'll find out what that's like and uh how we we do a variety of different things as far as wind is concerned, such as describing uh the different types of winds that uh we all experience uh from time to time, like the San Anás. This is kind of a San Ana condition, though we don't get the high winds, um, but we are getting heat. So there's a big high that's kind of hanging out, uh creating all this additional heat as the atmosphere just kind of hangs out, which is it's almost like stagnant air, you know, it just kind of hangs out for a while and gets us really hot. So hopefully this will move on quickly, but this is also part of spring and fall, so those two parts of the year where it's getting towards the Equinox, uh where we start to get, you know, could be rainy one day and then hot and sunny the next day. So that's unfortunately for our local mountains when it comes to skiing, you could have this like killer storm come through and, yeah, this is awesome, followed by a heatwave, which is a little frustrating, but it is what it is.
But we're going to talk about charting terms, things that you have to know when you look at charts, uh how to describe certain things, uh devices that we use as pilots to be able to determine the wind and and where it's coming from and how fast it's going, stuff like that. Um, we'll talk about the different forces that cause these winds, uh which is kind of nice to be able to look at a chart and know hopefully what's happening, um using charts to and visualizing the wind, which is very important. So uh, couple tips I'll throw out for you, uh rules of thumb, uh which will help you out quite a bit as far as flight planning goes, and then of course since we've talked about it since the beginning, the Coriolis effect, you will be getting uh some pretty good insight on what Coriolis effect is. I I will be showing uh two different videos; the first one's the most informative, the second one for visual learners is a little bit better uh when it comes to understanding storms and their rotation. Uh neither one of them is very long, um but they get the point across really well, which is kind of nice. So uh we'll also be able to find out uh what uh Bart Simpson has to do with the Coriolis effect; stay tuned for that.
So we'll start off with wind in the atmosphere and a definition; uh this is pretty straightforward if you kind of think about it, it's pretty logical, right? So air motion relative to the surface of the Earth, right? So it's just blown in a certain particular motion; uh it's also showing uh moving air. MKS uh can carry a bunch of stuff. So as I mentioned before and which we'll talk about when we get into clouds, in order to be able to get uh particulates into the air, uh particulates or are contained within different air masses and they move with it. So uh for an example, if you're over the ocean and you start, you know, an air mass is there for long enough, it will start to build up enough moisture and salts and everything else comes from the environment that it's hanging out over the top of, and as it starts to move like over Southern California and starts to let's say drop rain uh or any other, you know, type of precipitation, it also carries with it any uh pollutants, dust, uh or anything else that comes from the area in which it was hanging out. And we talk about global circulation a little bit later, not today, but on a different lecture, you'll understand that a little bit more. All right, so uh but pollutants I do mention that in here, and pollutants aren't necessarily a bad thing; it's could be just natural. Uh examples of that would be like volcanic plumes, right? They're not good, but they're natural; that's just something that happens.
Um, we also have things called some of the dust storms. If you've ever lived out in Phoenix or or in the Middle East, uh they have shamals or haboobs that come through, usually from a thunderstorm's outflow, and it creates this huge cloud, which I'll show videos on; you'll be able to see those because we don't get those in Southern California, um and they're kind of cool looking when they roll through, and uh even part of the video will show airplanes and how they divert, work their way around it before it actually shuts the airport down because they're they're pretty gnarly. Um, anyway, so pollutants aren't necessarily just like smog and exhaust fumes and that kind of stuff; it's it could be actually just natural stuff. Um, let's see, uh we'll be talking about the effects of of wind on the aircraft itself. We know from the very beginning of this uh this semester we talked about accidents that happen uh in aircraft, especially general aviation aircraft; wind is probably one of the the biggest reasons why there's either accidents or incidents, uh especially with smaller aircraft. We'll talk about turbulence, um especially later on when we talk, we actually going to have a lecture on turbulence, has some great videos that I I still enjoy today, even though it doesn't matter how many times I watch them, they're still kind of funny. So uh how we deal with turbulence and you'll see how, let's say a passenger might uh be affected by turbulence and they respond to it, but uh some some folks when they first start flying uh turbulence is an issue. So when we talk about that, hopefully will allay some of those fears uh if you have any in terms of how it will affect the aircraft and uh the flight itself, because nobody really likes the bad rides.
Talk uh wind shear is a big issue; we have a whole whole separate lecture on on that too, so wind shear is huge. Crosswinds of course, there's something you have to deal with as a private pilot; usually there's a limitation of whatever the aircraft's limitation is, but you can give a personal limitation to yourself. So when you're first starting off, uh you know the flight instructor might not want you to have much of a a crosswind, usually five knots or less, and then as you get more experienced and better at landing, he can increase that number or she can increase that number for you uh so you can get a little bit more proficient, um but practicing crosswind landings is a really good skill to have, and believe me it will totally pay off in the long run if you get really good at your crosswind landings. So uh tailwinds of course we'll be talking about those; those are the best, right? Versus headwinds which always slow you down and burn more gas, which is kind of a bummer.
Um, but now we'll kind of get into, we'll go from uh some of the things that we're going to actually be talking about and then we'll get into the terms themselves. So these are the things that you're going to need to feel comfortable with, uh especially when you're before taking tests and and all that kind of stuff, but just in general when you start to look at the weather. So you have to remember that wind is kind of omnipresent, right? It can go in a variety of different ways uh based upon it could be the terrain; it could be the type of wind, like a horizontal movement would be like an onshore where it comes in off the shore, and a horizontal movement; it could be vertical movement like a thunderstorm where you get wind shear uh from air flow going into it and coming out of it; uh so wind can go in in many different directions. Wind vectors, real important for a pilot to understand what a wind vector is. Um a wind vector is a combination of two different things, so the first thing of course is the direction in which the wind is coming from, and the second is the velocity or the speed of that wind, so both those together create a wind vector, so it needs to have both those components to be a vector. Uh the next is wind speed of course, so it's always in nautical miles per hour, not miles per hour; miles per hour is something you might see, let's say on the evening news when you watch the weather on on TV or something like that, they'll they'll convert everything in miles per hour because that's what most people can just kind of relate to, uh but of course for you know people that sail boats or fly planes, we use nautical miles per hour, so the difference is about 1.15, so if you want to do a quick calculation, you can; super easy to do if you remember that one, just in case you have a passenger; it's like, well, how fast are we really going, you know, because miles per hour always sounds better because it's faster. So whenever you tell a passenger, it's like, oh, always go with miles per hour, it just sounds bad, right?
And then of course wind direction, and this is a biggie. So uh the references for wind direction uh for the most part uh are given to you in true direction, now true being the latitude longitude uh of the Earth itself, right? So when they give you a wind direction, uh except there's there's a couple exceptions, um it will be in true. So if you were getting uh let's say a standard weather briefing, if you're going online and you're getting all your information about winds, you're looking at winds aloft, you're looking at a METAR uh in order to get your information that you need while you're doing your pre-flight and preparing yourself for wherever you're going to go that day, all those different sources will be in true direction, mainly because you use that information in order to plan your flight. So whenever you plan your flight, you always do things in a true direction first, so it's accurate, and then you convert it to magnetic based upon where you're located uh in the world, because there's little things called isogonic lines, so you'll find out that magnetic north where your compass points to is different from the actual true north where the latitude and longitude. So in other words, all those longitudes, they all meet up at the North Pole, so you'll see more that too as we get a little bit further along, um but just remember that wind direction is uh is referencing true north for the most part.
So let me tell you where the differences are, so you kind of have a heads up what you can expect. So there is a rule of thumb out there that tells you, and it makes it really simple if you're trying to remember like when you're taking a test, it's like, oh okay, I'm reading something; is that is that wind in true or magnetic, right? So this is simple; the rule of thumb is if it's written, it's true; if it's spoken, it's magnetic. There is a catch; there's it's a little one, but there is a catch to it. So for the most part, if you're reading something, going online, you're getting all your information, uh that's it's all going to be in true. The exception is when you're flying your aircraft, uh let's say you're flying your aircraft in the pattern, right, and the winds change a little bit enough for air traffic control to tell you what the new winds are. So the, you know, air traffic control, 1, 2, 3, 4 winds are now 220 at 4 knots, well the direction that they gave you is a magnetic direction because you're flying your aircraft and you need to compare that with your magnetic heading on your aircraft so you can easily see as you're coming in for a landing on Runway 20 where that wind or you can kind of visualize where that wind is coming from; really important. Now that's the only exception, um is is when you're flying; everything is given to you in magnetic. The one place that you can hear someone say it but it actually isn't true is this is the big catch is when you're talking to air, I'm sorry, almost said air traffic control, when you're talking to a briefer. So when you call a flight service and you get a standard weather briefing and you're you're chatting and about METARs and in-flight weather that kind of stuff, uh and they give you the information, they're speaking it of course to you over the phone. The catch is this is important; they're reading the information off of a screen where it is written. So anything you get from a flight briefer, unless they tell you it's in magnetic direction, will be in true direction; that's the only catch where if it's written it's true; if it's magnetic, if it's spoken it's magnetic; that's the only time you won't get it; they don't match out. You uh because think about it, think about it; is the only time you're going to hear magnetic is when you're talking to air traffic control or somebody on Unicom; air traffic control, ATIS, right? ATIS will be in magnetic uh because you're flying, you're getting weather information that you're flying with; they don't want you to get that information about let's say winds and have to pull out a calculator to figure out, oh, I need to convert it from true to magnetic while you're flying an aircraft, especially on short final; that doesn't make any sense. So that's that's the big difference.
So to understand winds a little bit better as far as vectors are concerned, we look at wind barbs uh whenever we look at the charts and so on. The left-hand side of this of this uh graphic you'll see of course our indicators; the circle with nothing in the middle in uh is winds calm, so there are there is no vector, right? Uh and then you go down the list: 5, 10, and 50 knots. So the five knots is just that little stubby line; 10 knots is a full line, and of course 50 knots looks like a little triangle, and then you can use a combination of all of these together except for wind calm because that's just by itself, um in order to to give you what you're looking for. On the right-hand side, on the top portion, you'll see uh compass rose; the compass rose gives you uh all your cardinal directions, right? So North, East, South, West, and then of course in between those two you can see little points in this compass rose, and those show the uh like northeast, southeast, and that kind of stuff as we start to move around, but you can see inside the compass rose there is a uh look at it like an arrow, right? So there's an arrow kind of pointing towards the center of the compass rose along with a barb or of the barb and the uh the indicator at the end showing you the speed, which I I liken that to like a if you think of an arrow, the feathers on an arrow. So look at it that way; I like to describe it that way; it makes it easy to kind of visualize it if you've ever shot a bow and arrow, even if it's fun or or whatever, you still have a little tail or or something on the end of of an arrow. So it tells you the direction of the wind is coming from in addition to the velocity. You can see down below of course that whole lower half shows you all the combinations that you can have, showing you of course how fast the winds are blowing, uh which is pretty wild. So variable winds are shown as it just depends on how variable they are; if they're under five knots for the most part you're going to get that little circle because it's not really an issue. So uh it is different on METARs, so when we get into METARs we'll show you there's a couple different ways they write that uh as far as calm because sometimes it they differentiate below five and below three knots, so we'll we'll talk about that later, so you have to worry about it, but for now you just need to understand the symbology that's associated with it because of course not only will you get a quiz on on the symbology, but you need to be able to look at it and just be able to tell and how you would use this practically, which is the whole thing I like to teach is looking at this 500 millibar chart.
So on this 500 millibar chart, it's kind of neat; the barb, the the straight part of the arrow stands for the direction the wind is coming from, and the the feather on the end of the arrow shows you the wind speed, so it's going to show you direction and speed are the two things, all right? So as we look at this chart, you can see not only uh the a whole bunch of the barbs uh kind of flowing across the the map from the west coast to the east coast, but you also see a couple other things, all right? So you see a low at the very top in red; you see a high down below on the left-hand side in in blue, and along with those uh the the wind speeds, you'll also notice rotation; you notice things are rotating, rotating around the highs and the lows, so can can anybody tell me the direction, clockwise or counterclockwise, that the wind is flowing around the low at the top? So lows always travel and in counterclockwise in the northern hemisphere; we'll ask Bart Simpson about this in a minute, but the lows go counterclockwise in the northern hemisphere, which most of us will fly for our entire lives, and then the highs will go clockwise uh in the northern hemisphere. The other thing you can see on this chart, which is the reason why I like to use it, is if you notice the speeds of the winds as they travel between the low and the high. So traveling, if you're sorry, looking at the the high, you can see obviously it's warmer, it's rotating clockwise; you as you start to travel up you can see it's like 20 knots; as you get closer you can it's like 35, 45; it's getting stronger; you get closer to that low, that southern part of the low, and all of a sudden you get 50, 60, 65 knots uh very very quick, and because of it in between the two it accelerates the air, which is kind of neat to be able to see on this one particular map, right? And of course in this case, this is a 500-millibar chart, which is that 18,000-foot level that we've seen in other videos or explanations showing that that's about where half of the pressure uh in our atmosphere exists. So this is a really really good chart; I'll be using it quite a bit in this class uh in different forms uh other than this one, right? Yes, getting closer to the high is where the speeds will start to increase; that's also where you'll get most of your weather, which you'll learn more about that a little bit later. Quick question about the barbs real quick, um which direction do they uh point or travel; the winds again, all right? So looking at the uh looking at this uh the compass rose in this picture, visualize yourself standing right in the middle of that compass rose; that's where you're standing, okay? So you want to know where the winds are coming from; they don't go to; they come; they come from, and the reason why they give them to you especially in aviation uh in in the from direction is because that's where you want to land your plane; you want to land your plane into the wind, so to land your plane into the wind you need to know where it's coming from; in other words, it's going towards the nose or yra, okay? Then then the common ways to measure the wind besides this very basic way to be able to show you where the winds are, just hold a flag up in the air; that'll do it, you know. We also have uh one of the most basic uh ways in order to tell the direction of the wind in aviation is it's one of the oldest; the wind sock; pretty straightforward; uh if none of you have used a wind sock before, uh it's fairly basic to be able to look at it and it will tell you the direction the winds are going, right? The easiest way uh I usually try to teach how to read a wind sock the best is look at the shape of the wind sock, all right? Now a wind sock works by of course as the wind blows through through it, it slowly extends further and further until it maxes out between 15 and 18 knots depending on what the fabric is made out of, uh and that's
About the maximum speed that it will actually show, if it gets about half that, uh, you know, that velocity, it’ll, you know, it’ll be sloping down about halfway. And then, of course, as winds get calm, it just kind of lays flat. All right. Um, but the easiest way to read a wind sock is to look at the wind sock as if it was a finger, and it’s pointing in the direction the winds are traveling, which is a nice way to think about it.
Now, if you look closely at this picture, you’ll notice that there’s a segmented circle that goes all the way around this wind sock. Uh, this wind sock can be found out at AAO Wells. So if you ever want to go out there with your instructor, it’s down towards San Diego, though it might take you a little longer as far as across country. But if the conditions are right, it’s a lot of fun to fly there. And I’m not sure if the restaurant’s still open or not, but if it is, it’s kind of a cool place; it’s something totally different for you to go, uh, go to. And then, of course, you get to be able to land on a dry lake bed, which is kind of cool. Um, but anyway, it has a segmented circle that goes all the way around it, and then you’ll see a line that comes off kind of to the right, down towards you, and to the right. All right. And that one is—it’s kind of L-shaped. I don’t know if you guys can see it well enough or not—that L shape is actually showing you the direction of the pattern. So in this case, if you were flying downwind, it would be a right pattern to come back in and land. And of course, you can’t see it on the other side; it also has the same L in the opposite direction. So if you’re coming in from the opposite direction, it would be a left base coming into the airport, which is nice. And essentially, that keeps you—if you were to be able to see this—uh, from not flying over the top of the highway, but over the top of the dry lake bed, which is kind of nice. So the segmented circle, of course, represents—of course, you’d be able to tell—uh, where the wind direction is relative to the runway itself. So the extended line of that L that goes right through—you’ll be able to visualize it better when you look over the top of it—uh, is the, the runway. And then you can see it’s really obvious; you’re going to be able to see the winds as you look down on it, the direction of your travel pretty straightforward, which is nice.
Other ways that uh, we can tell wind speed is using an anemometer. An anemometer looks like, like three soup spoons; all they do is spin around in circles really fast. Of course, it’s attached electronically to our device; it gives us wind speed. And most of them, when you see them, will actually have kind of like a, a, a metal uh, wind vane that’s on the top of it that will actually give you both. In this case, it’s just showing you wind velocity uh, as it spins around on that bearing, which is kind of nice. Uh, other ways that you can tell uh, wind is through wind vanes. So you can see this one; I picked this one because I like helicopters, which is kind of cool. It also shows you, just like all the others, uh, the direction that the wind is coming from. They weight the, the back half of the helicopter, in this case like the rotor, the rear rotor, uh, in order for it to swing. So as the wind blows against it, right, the tail will swing around, and the helicopter will always be pointing in the direction the wind is coming from, which is nice. So uh, you can visualize that that uh, whether it’s an airplane or in this case helicopter, is going to land into the wind in that direction, which is kind of nice.
Um, I’m sure a lot of you have seen this; it’s kind of trivia; it’s kind of off the subject a little bit, but has what, what norm like—if you see a wind vane on top of a, let’s say uh, like a farmhouse or someone, someone’s house or a barn or something like that, what is typically on the wind vane, like what kind of caricature or something that they have on top of the wind vane? A rooster. Is everyone wonder why they have a rooster? This is the trivia, so I had to write this down so make sure I say this correct. This is trivia. The Roosters from the 9th century, when uh, Pope Nicholas I declared that the rooster be placed on the top of every church to symbolize when St. Peter denied Jesus before the crow three times, that kind of stuff. But it actually was something that the pope told you to do way back in the day uh, when, you know, that’s what they did, and it spread, and then now everybody has roosters on top of the roof; they have no idea why they did it in the first place. So that’s kind of a fun little tribute for you.
Um, you can also use a flag to be able to—like the picture I showed before—but they actually have like lighter versions of the flag if you are more concerned about uh, you know, lighter winds. Um, you’ll see a lot of water treatment plants use it because of the chemicals they add to treat the water, and if any of those get out, of course, they—it doesn’t matter how light the winds are—they need to know what direction those, those are going. Right there you go; you got trivia and a wind sock all the same place. Look at that. Uh, wind descriptions, of course, uh, names of the winds. So we have—saw in the compass rose where it shows the cardinal directions—these are all the ones that are in between; also most of you have probably heard them before, like northeast, southeast, southwest, that kind of stuff. All right. So get comfortable with those descriptions because you’ll use them often. And if you can first get comfortable with the directions, and the second thing you need to get comfortable with is usually the numbers that are associated with that on a compass. Right. So we know like North is 360° or zero, right at North. And as you go towards the east, that’s 90°. So that means, of course, in between those two it would be 45°. So North would be zero; southeast, of course, would be 45°, and then 90° would be East. So as you get used to the numbers as you start to travel around the compass rose, you get a little bit more comfortable because when they start to ask you what the direction the winds are coming from, you’ll feel very comfortable uh, with being able to give an answer. It’s just a little tip for the future.
Um, catabatic. So we had a slight uh, Santa Ana kind of thing today, not really. Uh, they’ll start to blow a little bit later. Um, but those are what—the Santa Ana winds are catabatic. So you get a huge big high-pressure system that’s over the Great Basin, which is up by like Nevada. And as it starts to build, and if you think about the rotation of a high which runs counterclockwise, as it’s rotating, think big. So as this starts to rotate around, as it comes back, it’s hitting the backside of our mountains, um, and then going over the top of our mountains. And as it drops back down, it increases in its speed. So the velocity increases; it increases in pressure, which also increases the heat uh, that happens as it starts to blast over the top of the ridgelines. Then, of course, we get hammered with our Santa Ana winds, which makes landing well interesting, that’s for sure. Uh, things that they have similar to that uh, but on the, the north, the East Coast are the Nor’easters. Uh, that’s usually associated with a huge low that spins around, pulls a lot of super cold air in that has a lot of moisture in it, and creates a ton of havoc in the, on the East Coast; lots of rain, ice, and all sorts of crap. And uh, not fun to fly in at all. Uh, convective. Of course, need to understand what convection is, which we’ll get into more detail; you’ll know more about convective occurrence by the end of this; you, you’ll be good to go. Um, but essentially think thunderstorms when you think convection, and then some of the more kind of bouncy days that you have. All right. Um, let’s see. And then land and sea breezes, which we’ll talk about today specifically, which is kind of nice. Uh, the picture I put on this, on the right-hand side, that’s a—that you can tell the name of the stratospheric bone. This goes really high up in the air, and the whole idea what they’d like to be able to do is, is called a strat owl. And if they get these balloons that they figure out how to make them right, they get them to certain places where they’re actually kind of, kind of hovering in one place uh, kind of like a satellite which is geostationary or whatever, where it doesn’t move, and it just focuses on a particular area. The same thing you can do with these balloons; the guys, they’re getting better at it, but the whole idea is to be able to look at the nuance of the atmosphere uh, with something that just doesn’t like a reg wind b or uh, you know, wind balloons; as they go up, they go up to a certain altitude and they pop; they come back down. Right? This one will hang out, which is pretty interesting. So we’ll see how that works. They use a lar technology to be able to measure turbulence and all sorts of stuff to make our rides a little bit smoother uh, when we fly some of the bigger stuff.
So uh, now we’re getting into the forces that affect the wind. So there are three, three main forces that you’ll need to, you’ll need to know and feel comfortable with. The first is the pressure gradient force, which will kind of—you’ll get a good feel for this; it kind of makes—it’s pretty logical. Then there’s the Coriolis effect, uh, which of course Bart Simpson is going to play a part in. And then, of course, friction. So we’ll get into all the details of each, each individual one. We’ll start off with the pressure gradient force, and in this—we’ll go ahead—these guys are kind of goofy, but they get the point across; it’s pretty simple uh, about how to look at the pressure gradient force, when especially when you’re looking at a weather chart uh, on a Weather Channel. That is a lot of wind, yeah, that we had out there today. Well, you know what that means? What’s that, Vince? You’re breaking out the racket; we’re going back to Candela’s weather class days right now. This, this is a tried and true experiment, but it is one way to sort of show the wind on a day like today, and it’s all set up by the difference between high pressure and low pressure. And you can think of the high pressure is sort of being like a hill, and the low pressure is being a valley, and air parcels will slide downhill much like this racket ball slides down this clipboard here. Uh, the steeper the slope, the faster the ball will slide down. So the, the bigger the difference is between high pressure on one end and low pressure on the other, that’s a very steep pressure gradient, and that causes that wind to really—how great example today of just that in our, on across the country. Right. In fact, let’s take a look at that here with the, the radar and satellite. You can see that counterclockwise spin off to the north of us now, yeah, and the snow across the northern part of the state as well. So there’s our low-pressure area off to the north; we’ve got just a few spotty showers trying to roll through tonight, although the air now very dry here at the surface, so some sprinkles will be about it. So the area of low pressure is off to the north; area of high pressure down to the South across the Southern Plains. So there’s the top of the hill, so to speak; the bottom of the hill as Vince was talking about off to the north; that’s your pressure gradient or the change in air pressure. Air pressure of about 30 inches of mercury with that area of high pressure and a deep area, a strong area of low pressure off to our North right now, 29.2 inches of mercury. It is that change in air pressure that causes the wind. So that’s the reason why we had those strong winds gusting over 60 mph in some parts of southeast Wisconsin this afternoon. So hopefully that helped to explain a little bit more. One of the things I want to point out before I switch this slide is if you take a look at the high and the low, right, and you look at the pressure number, right, this would be the altimeter number that you would put in your Coleman’s window, right? So the high is at, at 30.0, and the low, which he called a deep low, is 29.2 inches. So it is a low low, right? But you can tell that the numbers don’t change a heck of a lot, right? So it only went down an inch or so uh, as far as the numbers are concerned. So that’s when you start to look at weather charts, especially when you start to look at them in millibars, which is that 1013.25; that’s what you’re going to see; you’re not necessarily going to see everything in standard numbers, but you’ll do a comparison between one area, like a high-pressure area and a low pressure; it’s a comparison between the two. I kind of want you to start thinking that way uh, that actually creates the weather or, in this case, winds that he’s talking about, which are 60 mph, which are nothing compared to our Santa Anas. So, but of course, they have nothing slowing it down in the Midwest; it’s kind of flat, right? Pretty good example uh, pressure gradient force. If uh, this makes it a little bit easier for you to visualize, when we look at these two columns of water uh, and in between them is this communication or this tube uh, if you were to visualize a valve on that tube that could stop the water from traveling from one side to the other, you would notice that you’d have more mass, of course, in the, in the tube that’s on the left-hand side versus the right. And of course, if you opened up that valve, that, that the water would travel from the high pressure to the low pressure. So if you’re starting to see a pattern, whether it’s you’re looking at your altimeter going from like high pressure to a low pressure, if you’re going from a hot environment to a cold environment, if you’re going from a lot of water on the left-hand side to less water on the right-hand side, from a high to a low, look out below, right? So it is very consistent; nature is very consistent when it comes to this kind of stuff. And the whole goal, of course, in this particular case, since we can look at this uh, example, is both those columns would actually like to equalize, right? So when we open the valve and that water starts to flow uh, it will get to a point, point where it’ll eventually just kind of even out, and both of those columns will be exactly the same. So that’s what nature would like to do, and like in the case when we’re looking at the weather chart, that’s what’s—that’s what nature is trying to do, but there’s actually nothing kind of stopping it, unlike a closed environment like these two tubes. Uh, the other environment is just kind of free and easy; it can kind of do whatever it wants. So things get in the way, and different pressures and altitudes and all that kind of stuff. All right. So uh, that’s the pressure gradient force; it’s pretty straightforward; it goes from high pressure to low pressure. All right. And how we would be able to use this example is something that we get here in Southern California. Um, we get—as I start to explain this—this is the—remember I’d mentioned earlier, I talked about uh, sea breezes and land breezes. Um, this is what we’re going to talk about right now. And to explain this a little bit better, this is a great graphic; this is—I think you’ll find this one in your book also uh, where this one is like the ideal environment. So there’s—this is where nature is in equilibrium, right? So if you look around this picture, you can see it; of course, we’re in a perfect world because that’s, you know, this is it, right? Stepford Wives, whatever—that was a weird movie, by the way. Anyway, so bad example, but uh, this is everything’s, everything’s in equilibrium. So whe—whether it’s the surface, you can see the temperatures are the same; the pressures inside these, these columns of air is the same. Um, if we started at the surface, which we can see is at 29.92, and we were to travel up and lose one inch per thousand feet, we get up to 2,000 feet, we see it’s at 27.92. So all that raw data is, is in a perfect world, right? Unfortunately, we don’t live in a perfect world, and so stuff will happen, and it’s usually—we can blame everything on the sun because this is what happens when the sun starts to rise. So as the sun starts to rise up, of course, we remember when we talked about uh, specific heat, right, in, in I think it was like the last lecture, where the water warms faster over a harder surface like sand uh, versus how the, the energy is absorbed by the water before the temperature starts to go up. So it can actually take in a lot more energy before actually changing temperatures itself. So that comes into play right here. So in this case, the sun comes up; it starts to heat the surface; as it starts to heat the surface, right, it starts to expand; as those molecules are kind of forced upwards, it kind of gets in the way of the molecules that are above them, and the pressure starts to increase as it starts to expand, right? So you can see by just looking at the numbers that are attached to this, instead of it being 27.92, right, which would be standard, it’s 27.95. So the pressure went up as the air is expanding below it, kind of forcing its way up. So it has to go somewhere, right? So it goes from a high pressure to a low pressure. Well, where’s the pressure lower? Well, over the ocean, because that’s not changing. So over the ocean, it’s still 29.92. So all that extra pressure that’s built up over the molecules expanding now gets kind of pushed offshore, and it starts to flow towards the, you know, towards the ocean. Well, as it starts to flow towards the ocean, of course, it starts to build up. At the same time, if you just look right below at the very bottom of this, and you’ll see an arrow that’s pointing from the ocean towards the surface. Well, there’s an example I like to use of a bucket. So if you go to the end of a dock and you have a bucket in your hand and you take that bucket and you dip it into the, into the water and you pull the bucket out really fast, right, is there a hole left in the water? If you look down, is there, is there a hole there where the bucket was? Like, no, there’s not. Why? Because the water fills it up; the pressure fills up that water. So when you pull it out, it comes in to replace it; that’s—you’ve created a low pressure when you pull the bucket out; there’s a low pressure where that bucket was. Same thing that you get here on the shore or on the beach or, or the surface; as the air starts to warm, not only is it expanding and pushing the atmosphere above it up, but it’s also creating a low-pressure area over the surface because of that; it’s now at a lower pressure over the surface. So all the air from the sea will now start to move in. So as you can see, if you kind of step back and to take a look at it, it’s a convective current, kind of like uh, if you think of a chain in a bike or whatever; it’s, it’s going back and forth; it starts to rotate in that direction. So if you’re sitting at the beach before the sun comes up, soon as the sun comes up, there’s a good chance you’ll experience an onshore flow as you’re just kind of hanging out there. Let’s say if you’re going to go surfing or something like that, um, you’ll be able to feel this happen, which is kind of cool. And it’s all about pressures, and the difference, of course, is eventually the sun goes down.
And the wind will change direction; it calm down to nothing, or doesn't do anything. And then eventually, because the surface will cool off faster than the ocean, this whole convective current will now reverse itself, and now you have a land breeze instead of a sea breeze. So there you go. Any questions about that? Something we get often also might be associated with some of the other stuff we're going to talk about, like marine layers and stuff like that.
So the um, the sun heats up the land more than the water, right? Well, the the energy that goes in is the same, except remember that specific heat—that the sand will increase in its temperature faster. Okay? And when it increases the temperature faster on the surface, it turns around and releases, through radiant heat, releases that into the atmosphere, which expands—you know, the molecules or that air mass that's above it. So that big parcel of air now starts to travel upwards or expands up, pushing everything that's above it upwards and creating more pressure as it's trying to get bigger. Oh, I'm starting to remember now. In the beginning, we talked about that—how the ocean kind of retains energy more, like, right? That's the specific heat of water versus the surface, right? The other—the water is like a battery because at night, you know, eventually it starts to release that energy it picked up during the day, and of course, now it starts to change a lot; it starts to change that whole cycle. So instead of the sea breeze, you get the land breeze, which is okay. All right, thank you.
It's also a good thought if you're riding a bike down to the beach on the road, River Trail. So keep that in mind. So remember when the Sun starts to come up, you're going to get a sea breeze, which means you'll get a tailwind if you start heading back towards Orange County from the beach up the river trail—just a tip. I love that one. So yeah, that trail is pretty windy; I know it. It does get really windy, and you'll notice it uh, if you still start playing it. So don't let the wind uh be in charge of you. So I ride that trail a lot, so it's it's a lot of fun.
Here's the biggie, right? So does the water swirl the other way in the southern hemisphere? Huh? But what do Bart Simpson—I don't know if any of you have seen this Bart Simpson episode; if not, probably want to go ahead and watch this one, you know, because you'll learn science while you're watching Bart, right? So here is the video, and uh, let's see. I don't know if it starts right away. Uh, this is kind of cool where they actually demonstrate how the Coriolis effect works; they give you an explanation, and then afterwards, there'll be a follow-up video on my next slide that is uh, even a lot shorter, uh, but it actually shows some storms and different ways to visualize the same concept. So go ahead and enjoy this video; I think you'll like it. I like this guy's stuff because he kind of speaks straight to you in an easy way to help you guys understand.
A couple of years ago, my friend Destin and I wanted to definitively answer the question: Does water actually swirl the opposite direction down the drain in the other hemisphere? At the time, I was living in Sydney, Australia, and Destin was in Huntsville, Alabama. Those are about the same latitude, just opposite sides of the Equator. So we created two videos that were meant to be watched simultaneously, and if you want to synchronize them yourself, you can click the link in the description. But we also recognized that that was a hassle for some people, particularly watching on mobile devices, and that's why I'm now releasing this extra-wide video of both videos synchronized. The Simpsons did a whole episode based on toilets flushing the opposite direction in Australia, plus other shows have supposedly demonstrated this effect. So I've seen documentaries that seem to indicate that which hemisphere you're in determines which way the water is going to swirl. But there's this other group of people, and they seem really confident that it doesn't matter where you're at—the water's going to swirl however it wants. So is this a real effect or not? The application of this principle to draining water in Earth's two hemispheres is just bunk. But if you ever just look for yourself and figured out which way your toilet swirls—if you try it yourself, you'll find inconsistent results. Here in Alabama, I've noticed that some turn counterclockwise and some go clockwise. This sink sometimes drains one way and sometimes the other way. You see, most toilets have little jets in it, so the swirl direction is determined by the design of the toilet and not which hemisphere you're in. In any container of water, there's always going to be some rotation; the water is not perfectly still, and it is this, rather than the hemisphere, that determines which way the water will swirl down the drain. So it's a myth; crossing the Equator does not mean the toilet's going to change directions.
But what if we come into the garage and do a more controlled experiment? But what if we could eliminate all motion from the water? This is a 1 1/2 m kitty pool. I have here a 5-foot-wide kitty pool. Instead of filling the pool with no vorticity at all, I'm going against the way it's supposed to drain; so I'm trying to fill it with the flow going clockwise. I actually filled the pool in the anticlockwise direction to be sure that any clockwise motion we see is not due to the way I fill the pool. So let's let the water settle for a complete day so that we know that it's perfectly still. And I've left this water sitting here for 24 hours, so it seems like I've damped all of the motions from the filling. Well, I'm not going to reach in and pull a plug out because that would induce some vorticity; I'm going to use this valve that I have connected to to the bottom of the pool. I really hope this works, Destin. Wish me luck. Good luck, Derek. I'm about to pull the plug. Okay, opening the valve in 3, 2, 1. Why should be flowing, and the pool is draining, but you can't see any motion of the water just yet. Okay, water's been flowing for a couple of minutes, and I haven't seen anything yet, so we're going to put some dye in it to help us see where the water's flowing. I'm going to put some food coloring in on the four cardinal directions around the [Music] pool. Check it out; it's like a tornado, like right off the bat. We got a counterclockwise rotation. We filled it up clockwise, and now it's going counterclockwise. You can clearly see that the water is flowing clockwise in this direction, and that makes sense because that's how it should flow in the southern hemisphere due to the Earth's rotation. We have a kitty pool in my garage, and the whole Earth is rotating, and the water is going counterclockwise because I'm in the northern hemisphere. It's real; this is real. But you can see what a tiny little effect it is and what extraordinary lengths I had to go to to see this effect. So really, you're not going to see it in a bathtub, and you're not going to see it in a sink or in a toilet because there are other sources of angular momentum that totally wash out this effect. We just proved it because we just eliminated variables. The Coriolis effect is real. There you have it.
It works. To understand how it works, imagine a pool with one edge touching the South Pole. Think about a pool near the North Pole. The pool is stationary relative to Earth, but every day it's actually completing one full revolution. The Earth is spinning on its axis, so the pool spins around the pole once a day. Now you can see the side of the pool furthest from the pole travels much farther every day than the side right next to the pole. The whole pool is moving, but the part that's closest to the equator has more momentum, and the part that's closest to the pole has less. So the outer side of the pool is moving fastest towards the east, and as you get closer to the pole, the velocity decreases down to zero. Think about these velocities relative to the drain in the middle. Now imagine we drain the pool. When we pull the plug, all the water starts moving towards the middle. Water from the far side is moving too fast relative to the drain, and so it gets out ahead, whereas water from near the pole is going too slow, and so it lags behind. The side nearest the equator is going faster, so that water outruns the drain, but the water nearest the pole is going slower, so it falls behind. So when the water approaches the drain, it swirls counterclockwise. This is the reason hurricanes swirl counterclockwise in the Northern Hemisphere, and this is the reason cyclones swirl clockwise in the southern hemisphere. The center of the hurricane has lower pressure, just like a drain, so the hurricane swirls just like our pool. The higher pressure air rushes into the eye of the storm, and just like in our pool, swirls in the direction dictated by the hemisphere. And that's the truth about toilet swirl.
So a little bit different visualization, same idea, but a different way to explain it to hopefully help you understand it better. If you've ever watched the news during a hurricane or wintertime nor'easter, you've probably noticed that big storms spin over time. As they travel in the northern hemisphere, they spin counterclockwise, but if you are watching a storm in the southern hemisphere, you'd see it spinning clockwise. Why do storms spin in different directions depending on their location, and why do they spin in the first place? A storm's rotation is due to something called the Coriolis effect, which is a phenomenon that causes fluids, like water and air, to curve as they travel across or above Earth's surface. Here's the basic idea: Earth is constantly spinning around its axis from west to east, but because Earth is a sphere and wider in the middle, points on the equator are actually spinning faster around the axis than points near the poles. So imagine you were standing in Texas and had a magic paper airplane that could travel hundreds of miles. If you threw your airplane directly northward, you might think it would land straight north, maybe somewhere in Nebraska. But Texas is actually spinning around Earth's axis faster than Nebraska is because it's closer to the Equator. That means that the paper airplane is spinning faster as well, and when you throw it, that spinning momentum is conserved. So if you threw your paper airplane in a straight line toward the north, it would land somewhere to the right of Nebraska, maybe in Delaware. So from your point of view in Texas, the plane would have taken a curved path to the right. The opposite would happen in the southern hemisphere; an object traveling from the equator to the south would get deflected to the left. So what does this have to do with hurricane spinning? Well, at the same—the center of every hurricane is an area of very low pressure. As a result, the high-pressure air surrounding the center, or eye, of a storm is constantly rushing toward the low-pressure void in the middle. But because of the Coriolis effect, the air rushing toward the center is deflected off course. In the northern hemisphere, the volumes of air on all sides of the eye keep getting tugged slightly to the right. The air keeps trying to make its way to the middle and keeps getting deflected, causing the entire system to spin in a counterclockwise direction. In the southern hemisphere, where the Coriolis effect pulls air to the left, the opposite happens; storms spin around the eye in a clockwise manner.
Uh, to answer the question that was uh, brought up uh, just a few minutes ago, uh, when we talk about the geostrophic wind, which is technically what you had brought up, uh, this is the difference of what—this is what happens to winds when you add one more component to it. So we originally talked about pressure gradient force, right? That's like simple—just like that—that clipboard with the ball; it just goes downhill, goes from high pressure to low pressure, pretty straightforward, super easy to learn. Uh, but of course, we know that stuff's always moving around in the atmosphere, and of course, now we have this Coriolis effect, which turns everything um. So if you were to get yourself in the upper air, that 500-millibar level, right, which is what that center picture is, you can see as that high pressure tries to go to the low pressure, it gets turned, depending on which side of which hemisphere you're in, and of course, in this case, we're showing the northern hemisphere in this example, uh, where it shows it going counterclockwise in a low and clockwise in a high. But either way, you can tell that it's curved instead of going straight like a pressure gradient force. Now if you—as you start to get closer to the surface where we take off and land our airplanes, now all of a sudden things change even more, and it really depends on what kind of surface that you're over the top of—whether you're in Southern California, where we're in the LA Basin, where we're surrounded by mountains, whether you're in the middle of Kansas, where it's flat as a pancake, right, or you're on the East Coast where they don't have—they they call them mountains, but you know, I mean, come on, really? I mean, 4,000 feet—that's the San Gabriel Mountains right here. Anyway, they're Appalachian Mountains, the same thing, of course. Uh, they have the same issue uh, in terms of turbulence that's associated with the surface. So as you get closer to the surface, uh, usually within 2,000 feet above or above ground level is what they considered to be a boundary layer, and only get confused because there's also a boundary layer in aerodynamics that I teach, which is about the width of a like a plane chord, which is very interesting; you can find different ways you can manipulate that in aerodynamics to give you more lift out of an object. But in this case, we're talking about the weather—the boundary layer in this particular case that gets affected by the surface is about uh, from the ground to 2,000 feet above ground level. So in other words, if you're in the Rockies, of course, it's going to start 10, 12,000 feet—that kind of stuff all the way up, right? Just 2,000 feet above ground level. What that does is now, because of the surface, you have to deal with friction. So as the air starts to travel over the top of that surface, it is slowed as it's trying to go in a direction; it's also affected by the Coriolis effect. So it doesn't have to be in the upper atmosphere to get the Coriolis effect, which is showed uh, in the videos, right? In the simple kitty pool, they showed that effect; so it happens all the time; it doesn't stop. Um, but with friction, it slows it down. So as you can tell, rotation isn't quite as as pronounced as it is in the upper air where there's no restrictions whatsoever on the direction in which the air will flow except for the pressures that it has to deal with. At the surface, though, of course, as it slows, it starts to mellow out that arc, as you can tell, as it starts to rotate around. It can also have a huge effect when we're flying aircraft because when you start to get friction on the air—this is the kind of freaky part—is you can actually get the surface winds going the opposite of whatever is happening in the upper atmosphere, and that could only be, you know, a few thousand feet uh, above it. So the example for friction that I give is a flight that I did from Kansas—I think it was Independence, Kansas—to John Wayne Airport. So I was delivering a 172, so we flew out there in a 421, picked up the plane, took delivery of this brand-new 172, and then we flew it back uh, two legs—so one stop at Albuquerque, and then then the next day we went to John Wayne Airport. And as we were flying back on the first leg from from Kansas to Albuquerque, we were hit with a huge headwind, which is pretty typical from the west coast to the east coast; that's generally speaking where the air flow is going to happen, uh, and that's what you you can anticipate uh, for the most part—kind of a headwind unless you get into some kind of system that gives you a tailwind. But for the most part, that's what you can expect. What we ended up doing, since we're in a 172, is we started playing around uh, with altitudes. So as the 421 was flying over the top of us at a higher altitude getting hammered by this huge headwind, we continued to drop down, playing with the GPS, trying to figure out where the best winds were, and right around 1,500 feet AGL, we ended up with a tailwind because of this—because of the friction that happened within the boundary layer—that was like super cool. So we went from a headwind—it was probably like 15, 20 knots—to like a 5-knot tailwind when we got closer to the ground. So super sweet, though we still didn't beat the 421, but whatever—it's a different story. Um, but the first one there has to, you know, by dinner, so he lost in the end, which is good. So those are the differences: pressure gradient force, Coriolis effect, and then Coriolis effect as it's affected by the friction on the surface. All right, hopefully everybody got that.
So now we're going to look at uh, some more charts, which is kind of nice, but we're going to look at charts at different altitudes. So in this first chart that we're going to look at, you'll notice that uh, the winds are some of them are kind of going in a consistent direction, right? So if you look at kind of in the Midwest, it's kind of going, you know, to the north; you look at the East Coast, it's kind of rotating from the east to the to the west, and then of course, there's a big gap in the middle where there's nothing, and then the West Coast—pretty typical—our winds are doing whatever they want, right? So looking at this chart, something kind of stands out that that is a little unusual, and this will help you on your chart-reading skills. If you ever see this, uh, can anyone tell me why there are no winds in the kind of the center of that map? So the center part of the map that's kind of a little bit off to the left is because this chart is showing 6,000 feet, and if you're familiar with the terrain over the United States in that area, you will know that we have the Rocky Mountains. So typically, you won't show any winds uh, lower than 3,000 feet AGL for the most part. So of course, at 6,000 feet AGL or 6,000 feet, of course, is below below the Rocky Mountains, which the winds aren't blowing um, and of course, so they don't show any wind. So yeah, that's that is definitely Colorado. Um, and then you can see, but the whole idea here, of course, is to take a look at one, the direction of the winds; two, remember that the settings when you start to look up weather, you have to really remember what settings you have—what altitudes—that kind of stuff, so you can anticipate what you're looking at, right? So we'll look at the next one. So the next one, we'll just walk you through this one, is at 18,000 feet—that's 500 millibars, or half the pressure of the atmosphere of the world—and in this particular case, we look at this; it shows winds from all directions encircling across the entire United States because in California, we have the highest mountain at what 14,500, I think, or 14,600 something like that; I think it just recently changed by like a foot; I can't remember. Um, anyway, uh, the nice thing is is it shows uh, no restriction on the winds themselves, and you can see more of a pattern. So you can see it now coming in from Seattle, dropping down in the Midwest as it rotates around through down through the Gulf. So what you're experiencing there most likely will be the jet stream, so it's the lower parts of the atmosphere are starting to feel the effects of the jet stream that most likely is above it, so which is pretty interesting. You can also see in the upper right-hand side, when you look over the East Coast uh, over like Maine and New York and that kind of stuff, you can see the velocity of the winds that are coming down from Canada. So if there was a lot of moisture, and this is wintertime, think about it—it's really cold in Canada, and there's a lot of water that's located right offshore. So as it's rotating around and it's going in higher speeds, it's going to pick up all that moisture, and it's going to dump all that snow and stuff like that. So that gives you kind of a taste of what a nor'easter would look like.
Even though this is not one, so at least you can start to see rotation now. As we go one more step and we look at 34,000 ft, somewhere around where the airlines are going to be flying, right? So as you see these now, it's very consistent, right? You can definitely see the direction in which the winds are flowing; that would be the jet stream. You can see the speed in which the winds are blowing. You can see, you know, like 45 knots, 50 knots. Go there's there's one which is kind of part of a a center of rotation which goes all the way down to five knots at 34,000 ft, but that's because there's rotation happening around it. And, uh, and then of course it's coming, it's whipping down, uh, going towards Florida. And then there's still some, I don't know, some weird stuff going down in Florida as the jet stream goes down and then comes up and off the west coast, and then it just keeps going. All right, so there's moisture you can see over that, the like the Panhandle or whatever, of Florida. Uh, and then you notice that the winds are different down in Florida; the rotation is different. Can anybody give me an idea of what that possibly could be?
So here is an example of what it looks like over Florida, where you would not want to be. So this is the time of the year when we have hurricanes. Uh, so if you keep an eye out on the hurricanes, we'll talk about them a little bit later. Hopefully, we'll get a really good one that doesn't like affect anybody, but yet we can kind of watch it as it starts to move, which is pretty cool. So you can see down in Florida that that really low low, uh, which of course is caused by the hurricane itself, as it goes over the gulf, picks up all that energy, all that heat that comes off the Gulf along with the moisture, and it continues to kind of fuel that fire as it starts to keep whipping around there.
And as far as I'm concerned, at this point, you have enough information for tonight. That's it, the end. So this was a morning ride; it's a lot of fun to do this. This was this is the river trail up more towards like, uh, going towards Corona. Go ahead, if you have a question, feel free. I do have a book, book suggestion up there: *The Wright Brothers* by David McCullough. That's like super good if you want to learn about the the Wright Brothers' process they went through to, uh, actually learn how to fly, because they were the first official CFIs. Well, not official actually, because they never got a certificate or even the first pilot's license. So anybody in my Ops class will know why that is. But, uh, good book.