 The reason I chose this topic is because if I have an area of specialty within geography, it's atmospheric sciences, namely weather and climate, mostly climate related, but especially El Nino. I did my master's thesis on how the different phases of El Nino and La Nina actually affect severe weather down south in the United States, especially in Florida. I did a statistical analysis of tornado type events, and there are certainly relationships between increased numbers and decreased numbers of tornadoes during the winter time, depending on which phase of El Nino or La Nina that we're in. But again, welcome. This should be about a half hour presentation or so, but as you know, we instructors tend to go off on tangents and talk at great length from time to time on various items. I'll probably go a little bit over that, but you certainly won't be here for an hour, that's for sure. Let's start out, first of all, talking about what actually El Nino is. I'll tell you what it isn't. It is not that periodic storm that hits the United States West Coast, especially California that you see all over the news all the time, with whip and rains coming in and large waves crashing into the cliffs, the cliff sides off the Pacific. That's not what El Nino is. Certainly an effect, certainly related atmospheric effects of El Nino, but what El Nino actually really is specifically El Nino itself, this is a periodic warming of the ocean water in the equatorial Pacific region. By the equatorial Pacific, we're talking about five to ten degrees north and south of the equator, five to ten degrees north and south latitude, so within a few hundred miles or thousand miles or so of width, but stretching across the equatorial Pacific. We're primarily concerned with the activity that's going on in the central and the eastern equatorial Pacific as opposed to the western equatorial Pacific. Not that that doesn't matter, but we're primarily focused on the central and eastern region when we're referring to El Nino. Now again, specifically, we're talking about warmer than average sea surface temperatures. This is actually not a new phenomenon. It's not something that we just discovered, it's not something that's in effect of global warming or climate change or anything like that. This was something that was actually discovered hundreds of years ago by Peruvian fishermen. They realized that every few years or so, these warmer sea surface or these warmer ocean temperatures would creep their way towards the western coast of South America here and it would drive away their fish bounty for the season and basically the fishing economy down in that region would suffer. Again, as early as the 1500s, this was identified. But why do they call it El Nino? Anybody know why they actually call it El Nino? Has anybody heard this story? You have? Okay. When did you hear this? Just a little while ago, right? Exactly. The fishermen basically realized that when these warmer ocean waters would start coming their way, it was usually right before Christmas time and again every few years, they would always seem to arrive early in the winter right before Christmas and El Nino in Spanish capitalized, if you were to be writing out, you capitalize El Nino, it refers to the Christ child. So they started calling it El Nino because it usually arrived right around that time of year. But again, every few years or so. So okay, so we see that there's warmer than average sea surface temperatures in this region periodically every few years. But what are the normal conditions in this region? Generally what you have in the eastern and the central equatorial Pacific region, what you have are much cooler sea surface temperatures and much warmer sea surface temperatures all the way in the western part of the region. Because that's your normal conditions as far as sea surface temperatures. As far as the atmosphere, how the atmosphere behaves, generally the winds are flowing east to west pretty swiftly along the equator. And it's kind of believed that these stronger winds that prevail going east and west called the trade winds, that these easterlies would kind of pile up the warmer sea surface waters over here in the western region, theoretically speaking. We don't know if that actually happens just yet. They're still trying to figure out what, I'll get into that later. But what we see again is certain definite atmospheric flow of the winds east and west. There's ocean currents along the equator flowing from east to west as well. So we have cooler sea surface temperatures in the eastern and central region, much warmer in the west. Those are our normal conditions. This results in pretty dry, in a pretty dry sky over in this region. Anybody know what desert is right along the South American coast here? Anybody know that driest region on earth? The Atacama Desert, very good geography major right there. Not only is this region blocking out winds coming from the eastern part of the continent, the Andes Mountains here are blocking that out basically. So any water vapor in the air, any humidity in the air has to rise to such high altitudes over those mountains that the cold air at those high altitudes squeezes out all the water vapor and dumps it as rain on the eastern sides of those mountains. So that blocks out humidity and water vapor from this side. On this side, you're right in the ocean, you think, well, gosh, they've got to have a lot of evaporation and water vapor in the atmosphere because of the ocean right there. Not really. The colder sea surface temperatures in this region do not really allow for a whole lot of evaporation. So the skies are generally pretty dry because of that as well. So this little strip of land that Atacama Desert is sandwiched right in between that. So that's why it's the driest region on earth. But we're more concerned with the sea surface temperatures at this point. But if anybody ever gets in to do a discussion with you about that region, now you can tell them. Cold ocean water, excuse me, and the Andes blocking out anything from the other side. So we see this normal pattern. This is what the normal conditions in this region. We started noticing this almost about 100 years ago now. Sir Gilbert Walker, he was a British scientist, did a lot of atmospheric research. And he was in this area. And he started taking measurements throughout this region. And he identified the same type of pattern. So generally what we have here is much higher atmospheric pressure from the subtropical highs, both in the northern and southern hemisphere. And the way that these guys rotate drive the surface winds westward. Not only does that happen, not only is everything flowing to the west, but in the upper atmosphere you have this return flow coming back. Now it's not as simple as this schematic here shows. There's obviously a lot more going on in the atmosphere than this shows as far as the different circulatory systems and all that. But eventually, generally speaking, anything that flows at the surface west rises up higher up into the atmosphere in the western region. And as it cools and spreads out, it eventually makes its way back to the east and descends. Now again, not as simple as that, but it's a general idea that still stands today. So he identified this normal circulation which he named after himself, of course, the Walker circulation. But he also identified that there are changes in the circulation that happen periodically every few years or so. Okay, that sounds familiar, right? So what he noticed was that every few years or so these trade winds, these surface trade winds that blow to the west, slow down, they weaken. And because of that, this Walker circulation, this whole east to west flow and then the return flow at the upper altitudes before it descends and starts the whole process over again. It starts to weaken and the whole geographic, pardon me, the whole geography of the system starts to shift to the east. Not only does it weaken, but the geographic area that it covers is reduced as well. And the center of all the action, basically where the air makes to the west warms and rises because of the warmer sea surface temperatures. Basically the warmer the sea surface temperatures you have, the more evaporation you're going to have, the more energies being given off at the surface, the more warm air you're going to have rising. He noticed that that action center that you normally have every few years shifts to the east. And because of that, this Walker circulation kind of slows down and dies as well. This coincided with different atmospheric pressure systems increases and decreases in these. And he started, he named this the Southern Oscillation. That, if you think of the term oscillation, something that goes back and forth, right? What he noticed was that every few years, the high pressure in the eastern part of the region would get much lower. And then the lower pressure that's normally dominant in the western part became much higher. Now they didn't flip flop, but there were certainly drastic changes in these that caused this whole Walker circulation to the intensity to slow down. And for the eastern geographic shift that he had recorded. Now he also started realizing that, hey, the people down in this area, they talk about how the sea surface temperatures are always becoming much warmer every few years. Coincidentally, these changes in the Walker circulation, what he identified eventually as something called a Southern Oscillation, coincided with these warmer and cooler sea surface temperature episodes. Or this El Nino that came about every few years, the warmer than average sea surface temperatures in this region. What you're looking at here with these two maps, schematics I guess you could call them. Again, your normal conditions. If you go back a couple of sides here and you look at the normal Walker circulation, and then the normal conditions on top here, you see that that coincides with the map here on top. The warmer sea surface temperatures are confined to the western part. And then the central and eastern areas are much cooler. But when this Walker circulation collapses and starts to shift to the east, you see this spreading of the warmer sea surface temperatures starting to spread east. So eventually they come up with something called El Nino Southern Oscillation. If you're ever reading through the media and you see the acronym ENSO, ENSO, that's what it stands for. The term is still used nowadays, but more and more common, you're going to hear scientists refer to this whole thing as El Nino and La Nino. La Nino is part of this Southern Oscillation El Nino thing. And I'll get to that in a minute. But generally when you hear this term, that's what they're referring to is the relationship between the changes in the atmosphere, the different pressure signals, the Southern Oscillation, and then when El Nino arrives in the eastern part of the region. So the problem right now with scientists and they're still trying to figure out, and we have all these really cool models, all this technology, we have far more atmospheric and oceanic data than we've ever had, but we still don't really have enough to tell us which one of these guys is happening first and which one triggers the other one to happen. Do the sea surface temperatures in the eastern and central region, do they warm up first causing changes in the wind patterns and the atmospheric pressure patterns? And for the whole Walker circulation to shift east? Or are there changes in the atmosphere first that allow the sea surface temperature patterns to change? They still don't know yet. They have been run, there are so many different studies out there on coupled ocean atmospheric models. And what a coupled ocean atmospheric model is, is taking all the measurements from the ocean, you're taking the sea surface temperatures, the current direction, the current speed, all the different variables of the ocean. And now you're tying that information in with atmospheric dynamic information as well. Wind direction, wind speed, temperatures, humidity, all that different stuff. So they're taking all this different information and coupling it together from the ocean and from the atmosphere. It's a very difficult process and certainly well beyond my understanding, that's for sure, these are the stuff like physicists do and people who are specialists in statistics and calculus and all that. Not me, I'm a geographer. But they're still trying to figure out which is the primary forcing agent? Which one of these guys changes first and causes the other one to switch? Is the ocean change first or does the atmosphere change first? Affecting the other, still don't know yet. You're probably thinking, well why is this guy up here talking if they don't even know what's going on yet? Because it's still a very interesting system. We actually do know a lot about it and we actually predict what's gonna happen. We just don't know which one is causing it. It's kind of weird, I know. Okay, let's get into what La Nina is now. Contrary to popular belief, the media, your friends, even sometimes weather people, your TV meteorologists for instance, these guys aren't always the biggest expert on everything out there. They might be good with weather prediction in their own local area, but I've even heard them miss speak often about what La Nina is, what El Nino is and how these things work together. But contrary to popular belief, La Nina is not the complete opposite of El Nino and El Nino is not the complete opposite of La Nina. They're all part of the same system, but what La Nina really is is actually normal conditions, just on steroids. You're talking very amplified normal conditions. So what we see with normal conditions is cooler in the east and central as far as sea surface temperatures, warmer in the west, but now this effect is even stronger. It's even colder than normal in the central and eastern part and warmer than normal in the western part. Again, as far as the sea surface temperature is alone. This really wasn't something that was discussed or talked about until like the 70s or 80s. Scientist named George Flanders, the first one who actually published something called El Nino and La Nina in a research paper in the monthly weather review. I believe that's what it was. Certainly one of the big geek climate journals or weather journals that's out there. But this is something that's relatively newer, I guess, relatively speaking with this type of research on this topic. So again, it's not the complete opposite of El Nino. It's actually just normal conditions but amplified. And again, El Nino is not the opposite of normal conditions either. It's more of a weakening or a relaxing of normal conditions. And I'll get to talking about that a little more as we go on here. Now let's look deeper. And in quotes I have that up there for a reason. Let's look deeper into what El Nino and La Nina really is as far as their sea surface temperatures. Why are the sea surface temperatures warmer and cooler in different areas? Basically the sea surface temperatures, we're talking about the temperature of the water at the very surface where the boat would hit the water, where your feet would land in the water if you jumped in. That's where the temperatures are taken. That is what's most important when we're trying to determine how much evaporation is being given off from the ocean. Again, cooler sea surface waters will not evaporate as much as warmer sea surface temperatures will. But there's something that controls that and something called the thermocline and that's many feet underneath the sea surface itself. Basically what the thermocline is, is a boundary layer between the upper, lighter, much warmer water on top versus the much denser and colder layer below. So if anybody's ever done any diving or been in the ocean, I know I haven't, but excuse me, I'm just getting over a cold here. But if you know anything about the ocean itself, there is a distinct difference as you go down in the ocean. You're in a much warmer layer until you hit this thermocline and boom, you're in extremely cold water and much denser underneath after that. And it's not just the temperatures, it has to do with the salinity of the water, how much salt is in the water and those types of things as well. But the deeper that thermocline is, the more warmer water is gonna be on top of that. The deeper that pool of warm water, the more evaporation is gonna be given off by the sea, by the surface. The more energy can be held in a deeper pool of warm water. Think about filling your kids, some of you if you had children, filling your kids pool when they're kids. You fill it this much with warm water, it's gonna give off a certain amount of evaporation. But the more you put in there, the deeper layer of warm water you have, the more energy is gonna be held in that. Think about that on continental scales or world regional scales. Think about that added energy, the deeper the layer of warm water you have. It's certainly different throughout the equatorial Pacific. The normal conditions, our thermocline depth is pretty shallow in the eastern and central part. It gets deeper as you go west, but the shallower area of the thermocline is where you have less warm water above that. So there's gonna be not as warm sea surface temperatures and not as much evaporation being given off into the atmosphere. Whereas in the western part of the region, it's much deeper, far more energy, far more evaporation, far more activity is gonna result in the atmosphere above that. And I'll get to how that happens soon. During El Nino, this thermocline doesn't flip. So it's, again, El Nino is not an opposite effect. It's more of a relaxation of your normal conditions. This thermocline depth in the far west gets a little shallower, but it certainly gets much deeper in the central and eastern region. It's not really a seesaw effect because a seesaw effect would go back and forth like this, right? This is more like a lazy or a half seesaw effect where you have sort of a straightening out of the thermocline, but it never does quite straighten out. It's always gonna be deeper in the western half of the region. But again, the differences in the depth will determine how much energy is given off from that. So even though it's always deeper in the west, you can still have cooler than average sea surface temperatures in that region, although it's still warm, okay? So what we have during El Nino, again, is this kind of a flattening out, or at least not such a sharp incline from the east to the west. This cools, again, slightly the sea surface temperatures in the west, but it drastically increases the sea surface temperatures and the central and eastern part of the region. During La Nina now, as we know, is, again, amplified normal conditions. Normal conditions on steroids, if you would put that in your notes, that's a good way to think about it. But we have a much deeper than normal thermocline now in the eastern, pardon me, in the western half of the region, and much shallower than normal in the central eastern part. This allows for cooler sea surface temperatures in the central and the east, less evaporation of the atmosphere, less humid in the air, far less atmospheric activity as far as clouds and rain in that kind of atmospheric activity. So these changes in the thermocline depth coincide almost directly with the changes in the sea surface temperatures. There's always a little bit of a lag. When it comes to oceanography or when it comes to studying the ocean and its energy, there's always a little bit of a lag effect when, let's say, the thermocline depth changes. You're not gonna see those sea surface temperatures change immediately, but you will certainly see that within a few days to a week or so. Same thing with the atmospheric effects. It's amazing how quickly the changes in weather patterns and the changes in the atmosphere directly above will react to the amount of energy being given off by the ocean. And I'm not talking about the immediate region itself, but more distant regions as this energy that's given off by the ocean in the form of evaporation, in the form of water vapor in the air, how quickly that can travel to distant global regions. Okay, so again, just more of a specific look here at how this all works together. We've just talked about the thermocline depth and how that affects the sea surface temperatures. Now I'm gonna get into a little bit more how this actually affects the atmosphere. I've talked a little bit about it already. I'm gonna go into a little more detail. Again, the deeper of a pool of warm water we have, the warmer the sea surface temperatures are. The warmer that is, the more evaporation gets given off. Basically what drives our atmosphere is heat. That's one thing that's your typical person who watches the weather every day and knows a lot about it doesn't appreciate how much the atmosphere is actually driven by heat. Whether it be from heat coming off of a dry surface from the sunlight warming it up, and that's another misconception. The sunlight does not warm our atmosphere. It warms the surface. The surface warms up and that energy given off by the surface is trapped in by many different gases that make up our atmosphere. But there's a very small amount of gases in our atmosphere called greenhouse gases which everybody hears a lot about with global warming and climate change and all that. But it's a very small percentage. And this small percentage of our atmosphere traps in all the energy given off by the surface. So the warmer the surface gets, the more energy is gonna be given off into the atmosphere and gonna be trapped in by our atmosphere. The ocean works the same way, but it works a lot slower when it comes to warming up and cooling down. Any wet amount or anything wet will warm up and cool down slower than anything dry. And why is that? Well, basic physics will tell you that. I don't know what it is about water that does that, but now let's look at the fact that light penetrates water and it goes several feet down into it. So you're not just warming up the immediate surface like you are with land. You're warming up like an inch or so or less of the earth's surface when that warms up. In the ocean, the light penetrates because water is translucent. It goes all the way, many feet down and it has that much more to warm up on top of it. So that effect is very slow. Nevertheless, the amount of energy given off by the ocean is gonna be a lot more than the surface because there's a lot more water vapor given up in the form of evaporation. Evaporation not only is water vapor in the atmosphere, but it also contains a hell of a lot of energy and heat as well. And we'll talk about some of the effects this winter and you have every winter with El Niños and how that can moderate temperatures in the US, especially, but I'll get to that. Not only does it drive the air temperatures as far as the amount of water vapor in the air, but it also determines how many more clouds and rainstorms you're gonna get. Obviously, the more humidity you have in the air, the more potential you have to form clouds and rain, right? Okay, so our normal conditions do look like this. You have this cooler sea surface temperatures in the Eastern and Central, not given off much energy. Generally, a lot of clear skies in this region, not so much in the West, pretty much have these constant daily thunderstorms because of it, because of all the warm water in that region, given off evaporation. Now during El Niño, as we see, the circulation kind of weakens and shifts over to the East, but the storm clouds follow. Now we have much warmer than average sea surface temperatures in this region, so you're gonna have a lot more storms developing in the Central, not as much in the Eastern part as much, although you do. When I was talking about the Atacama Desert earlier, look up online tonight, when you get home and you're playing on your computer, look up Atacama Bloom and they'll show you the whole large areas of this desert that completely bloomed every square inch of the desert surface because of a large rainstorm that they had go through there. Some of these areas of the desert don't get rain for 10 years, so you can appreciate how dry this is. Well, because of that dry, any seedlings in the soil and all that sit there stagnant, but if water touches them, they'll activate and they'll grow, and some of the rains that were brought to this region by El Niño this year made some really beautiful landscapes in this region. You should, again, look that up if you ever get the chance, it's pretty cool. But generally speaking, we have a lot more, again, a lot more cloudier conditions in rain in the Central and the Eastern part, but more specifically the Central part of the region. And again, La Niña, now we have, again, stronger than normal, stronger than average, normal conditions. Just basically increases the intensity of everything that happens otherwise normally. So don't really have much of a displacement of anything, but you certainly have drier than average conditions in the Eastern and Central, and more energy. I wouldn't say more rainfall as much, but certainly a lot more energy in the Western region for sure. We're not concerned of that. We're more concerned of how this is gonna affect us here in the U.S. Before I go into the details, though, I wanna show you a few maps here of what we can expect on your average El Niño winter and your average La Niña winter. And I'll explain why we're looking at winter specifically as opposed to summer in the slides that come. But what we see in the U.S., as far as temperature anomalies, anomalies are departures from your average during El Niño, on the left here for temperatures. In the upper part of the country, we generally see warmer than average temperatures. Don't let it fool you, this red. It's not hot up here in the wintertime. We know that. What that's just showing you is the departures from average using different shades of color to make things really stand out. Like, yeah, this area is quite a few, it's a few degrees warmer than average up in this region, generally in your El Niño winter. And down south, it's generally cooler. Probably thinking, how is it that? I'll get to that. But now let's look at the precipitation or the rainfall or snowfall anomalies associated with El Niño as well. Generally up by us in the upper Midwest, we see a little bit more than normal snowfall. Some years, I mean, I can remember being in college when, during the 97 El Niño. And it was a pretty strong one and we had a lot more snow than average that winter. But the temperatures were generally around average to a little bit above average. So, but we can maybe expect a little more snowfall. It wasn't predicted for this winter. I'll get to that as well. But what you really see as far as precipitation in the United States is increased rainfall in the south, along with the cooler temperatures in the south. And you also get a lot more rainfall along the California, especially the California western coastline. What about La Niña? Now, although El Niño and La Niña climatically are not opposites, you certainly see the opposite effects though on the United States, especially in the southern United States, you really see it. You can expect warmer than average temperatures. I don't know what happened with Florida here, but Florida should look like that in this one. I got this, for whatever reason, I couldn't find any data that was better than like 2000. Everything was like from 90s and lower. And we're talking like from the National Oceanographic and Atmospheric Administration website. For whatever reason, they just don't have a lot of published more recent maps. I know they have them out there. I know the research has been done, but I couldn't really find anything. This should show at least yellows, if not up to reds. Florida especially is much warmer than normal during the wintertime, during the winter months. And so is a good part of the nation's midsection. But basically the warmer temperatures creep up to the north during La Niña winters. At the same time down south, you see much drier conditions as well. Okay, again, I'll explain what this is, but if you know anything about the U.S. south, especially Florida, you know, that Florida has basically gets all their rain in the summertime and during the wintertime, it's not saying they don't get any rain at all, but far fewer days of rain during the wintertime down there. But during La Niña, he's even drier than normal. Well, what explains these different types of patterns and what explains winter weather in the U.S. in general? Well, in general and associated with El Niño and La Niña, it depends primarily on three things. How much water vapor, how much humidity is in the air? Generally our winters in the U.S. are very dry. You know, around here, generally you walk around all winter touching anything and you're just like, I don't want to touch that because I'm gonna get shocked, right? Like this winter, I've hardly walked around that all and touched something and you know, got buzzed. There's been a lot of extra humidity in the air. But our winters, especially in the upper half of the country, the northern half of the country, you know, the amount of water vaping there, the amount of humidity is huge. When it comes to determining what kind of winter you're gonna have as far as temperatures and as far as snowfall. So the amount of water vapor in the atmosphere flowing over the United States. And I'm talking flowing over from west to east from the north, from the north half of the Pacific flowing west or probably flowing to the east over the continental United States. The size and the strength of the subtropical high pressure system over the northern Pacific. Now, I don't mean over the north part of the northern Pacific, just the north Pacific closer to the equator. The subtropical high is actually much closer to the equator, but in the northern hemisphere. And depending on that, depending on the size and the strength of the north Pacific subtropical high will determine the average position, the seasonal mean position, the seasonal average position of the jet stream. And if, most of you are here because you probably know a little bit about the weather. The jet stream for those of you who don't know a little bit about the weather is basically this rapid flowing tube of air in the upper atmosphere. And that's the boundary between the warmer tropical air masses to the south and the much colder and drier air masses, polar air masses to the north. How that tube or that river of air in the upper atmosphere gets going is basically a sharp drop between the top of the atmosphere where it's in the warmer part of the world and a much thinner or a much, how would I describe this? I guess a more thin layer of atmosphere over the colder parts, northern parts of the earth. But there's a real quick drop between the tropical air masses and where the polar air masses are. And the upper level atmospheric pressure that results from that basically creates a steady stream of rapidly flowing air in the upper atmosphere. And that, as you know, is often that boundary area of where the warm and cold air masses meet. This is where you get a lot of your storm activity, where you have warm and dry, warm and colder air masses beating and creating clouds, rain, storms, whatnot. So these three things are determining what kind of winter weather we're gonna have in the US. And again, winter is more important because our atmosphere is normally very dry. You can put a huge influx of water vapor into the air and all of a sudden, things change. During the summer months, not as much. We're humid anyway in the summer. We have much more humidity in the air in the summer. An influx from the Pacific isn't gonna change things that much because we get plenty from that big bathtub called the Gulf of Mexico down to the south of us. That basically is what drives the eastern two thirds of the United States as far as summer weather and as far as the warmer temperatures. But nevertheless, sea surface temperature conditions all the way in the equatorial Pacific from the central or from the eastern central and western part of the Pacific. The sea surface temperatures in this area are what determine these variations in the amount of water vapor we're gonna have in our winter time. The size and the strength of the subtropical high in the northern half of the Pacific. And because of that, where our average jet stream position is gonna be throughout the year. All right, so a little more detail about the evaporation, the effects of the evaporation here. Again, as I've explained, the warmer the sea surface temperatures, the more evaporation is gonna be given off, right? This is more of a, this is more important when we're looking, especially at the central equatorial Pacific. We have the subtropical high that sits right about here, this north, again, this north Pacific subtropical high. The more evaporation that's being given off in that central region, the more of that water vapor in the atmosphere is gonna make its way into our subtropical high. The northern flank of that subtropical high in my hands going this way, I use my laser pointer for this. Subtropical, or pardon me, high pressure systems rotate clockwise. Okay, so we have this guy circulating around right here. And as you can see, as he swings down to the south, he's gonna be picking up a lot of that water vapor in the atmosphere given off near the equator in the central region. And as that flow swings northward, it's gonna be carrying that into the middle latitudes where we are here in the United States. Well, this isn't the only subtropical high pressure system. There's many of these throughout the world. There's a whole series of subtropical highs on both sides of the equator, straddling the equator on both hemispheres, as well as a series of low pressure systems called the equatorial low pressure belt or something called the intertropical conversion zone for those of you who have physical geography with Dr. Sharkey right now. But so we're primarily concerned with what's going on here in the central because if it's warmer than average here in the central and eastern equatorial Pacific, that's where our north Pacific subtropical high is gonna pick up that additional water vapor and carry it over into the United States. So again, during an El Nino where sea surface temperatures are warmer, more evaporation, more water vapor, more humidity making its way into the U.S. during La Nina, cooler than average sea surface temperatures in this region, much less than normal. Well, what about the high pressure systems? How does that affect the high pressure systems and the position of the jet stream and all that? The energy, as I was talking about earlier, the depth of the thermocline, the depth of that warm water pool determines the amount of energy through evaporation but just energy in general that drives, that drives these subtropical highs. The warmer the sea surface temperatures in this central region here, the warmer those are, the faster and stronger this north Pacific subtropical high is gonna rotate. Think about sticking your hand in a bucket of water and you're turning the water around, right? You're doing it slow. You see that kind of little dip in the water in the middle, that swirl in the water. You see it kind of start to dip a little bit, the faster you start turning it, right? Our pressure systems work the same way. The more intense they are, the more they're actually gonna constrict and become tighter. The slower they're moving or the less intense they are, the more they're gonna expand. The jet stream, whoops, I keep doing that. The jet stream here, this is kind of a bad example but really what this should show right here is the jet stream touching this northern flank of the subtropical high in the Pacific. The jet stream rides right along the northern flanks of all the subtropical highs. The way that these guys rotates and look how here in the north, the rotation is pushing from west to east and all of these subtropical highs. So basically the northern flank pushes the jet stream from east to west, so to speak at the surface as far as the surface level wins. But it also does so in the upper atmosphere. Again, with this big dip between the layers of the warm and the cold air, also driving this jet stream. But that position of the jet stream is, sorry, that position of the jet stream is determined by where the northern flank of the subtropical high is. Again, if it's rotating tighter and faster, if it's stronger and it's rotating tighter and it becomes smaller, it's gonna bring down where the jet stream is. It's gonna bring it farther to the south because this whole thing shrinks. So as this thing shrinks and becomes tighter, that jet stream's gonna come farther south with it. Just the opposite during La Nina. If this thing is weaker than normal, it's gonna be much larger than normal and it's gonna be moving slower. So the jet stream's not gonna be moving as swiftly and it's gonna be pushed up farther to the north. Okay? Now we're gonna get probably the most complicated part of all this. This is another one of those theoretical type diagrams. This isn't exactly really what happens. But these subtropical highs are driven by something theoretically called a Hadley cell, a scientist named Hadley obviously identified this. But let's say you're on the equator and you're in the far western part. So you're standing right over here. And you're looking straight east along the equator. So you're looking at the west coast of South America there. This is what you'd see. This would be the northern hemisphere. This would be the southern hemisphere. Let's focus over here. The rising warm air at the equator, as the warm air rises, it gets into the upper part of the atmosphere where it cools. You know, the higher you go up in altitude, the more it cools, right? The more water vapor that's in the air, when it hits cooler conditions, starts to get squeezed out like a sponge. While the water vapor molecules start to slow down, they start to bump into each other and stick together, form larger droplets of water. Eventually you can see these water vapor particles come together in large bunches called clouds. And if the collision of those droplets of water and begin to coalesce or stick together and form larger droplets, eventually they'll become too large. They start falling out as rain. Gravity pulls it down naturally. That's based in a nutshell. That's how a cloud and rain formation happens. But as that happens, as this warm air rises into the upper atmosphere and all the water vapor starts getting squeezed out, it gets dumped out as rain, but the air starts to then spread forward. So it's spread towards the North Pole. And as it starts to spread towards the North Pole, it starts to descend because it's now cooled. The condensation process actually, it's as the water vapor squeezed out of it. Now they get this dry air flowing, sorry, flowing forward and because it's cooler, now it starts to descend. Now I'm not talking like much cooler, but nevertheless the cooler the air is, the more it starts to drop versus the warm air that rises, right? This northern end of the Hadley cell, God, I keep doing that, I'm sorry. The northern end of this Hadley cell where the cooler air starts to descend is actually the subtropical high-pressure belt. This is that North Pacific subtropical high-pressure cell that I was showing in the previous slides. So you're looking right here. This is where a subtropical high is. Now you have this return flow again towards the equator and then the whole process just kind of continues. It's something called a positive feedback loop where it's just a process that amplifies and kind of grows upon itself. But it's more or less of a never-ending cycle everywhere along the equator in both hemispheres. But it's what drives the subtropical highs. The descending of the cooler air and the northern part of the Hadley cell creates the subtropical highs, okay? Now this is actually what's affected by the amount of water vapor in the atmosphere and the amount of energy being given off by the ocean. Earlier I told you how the subtropical highs will expand or contract depending on how much energy is being fed into them, how powerful they are. Well this happens, the same thing happens to the Hadley cells. So the more energy you're gonna give off into the Hadley cell the tighter this guy is gonna start rotating and he's gonna start, the northern extent of it is gonna be pushed towards the equator thus bringing down that jet stream location which rides along the northern flank of it. So we'll look at some specific examples. But nevertheless what you see here at the Hadley cells is gonna determine the strength of the subtropical highs and thus the position of our jet stream. Again separating our colder air masses from the north and our warmer air masses to the south. So this is what really determines what kind of weather you're gonna have at any given day and looking at the average jet stream position throughout the winter or throughout a season will determine what type of season that you had as far as temperatures and precipitation as well. As we know that the storm track generally follows that boundary between the warmer and the cold air masses. So during El Nino, I took these, I couldn't find anything cool online that showed like a live diagram or any kind of like animation or anything like that. I couldn't find anything really cool so I just took these things and I took this image and I shrunk it this way to give it the effect of this Hadley cell is rotating tighter now as you can see. But in essence that is what happens. The warmer sea surface temperatures will make this thing spin faster and as it spins faster it contracts. Now where you have the cooler air from the atmosphere descending and creating the high pressure cell is a lot closer to the equator than normal because it's being, because of the intensity of it has been amplified. So this will bring the jet stream, that's the average jet stream pattern which again rides along that northern flank of it. It brings it farther to the south bringing with it cooler air from the north and giving it the area where the warm and cold air masses meet allowing more rain or cloud formation and eventually rain and storms to develop as well. Now during La Nina we have the opposite. Now I took this image and stretched it to give it the effect that hey, we have not as much energy rising in this central equatorial region. We have a lot less so this thing isn't spinning nearly as fast and because of that it's much, it takes up a larger geographic area than normal. Now we have the descending air from the, sorry. Now we have the descending air that forms a subtropical high pressure system much farther to the north, much farther away from the equator. Bringing that jet stream position again which rides along the northern part of it keeps it farther to the north instead of tugging it farther down to the south. Okay, so that's what we normally have during El Niños and La Niños. We normally have in our region here in the Midwest. We normally have a little bit, some warmer temperatures, warmer than average temperatures by a few degrees on average and usually a little bit more precipitation usually in the form of snow. And down south we have much cooler and wetter conditions during El Niño. Okay, so like what happened this winter because we're not really seeing that this winter? We certainly had, we probably are having warmer than average temperatures but keep in mind we have three weeks of winter left folks. It's not March, it doesn't mean, or it is March, it doesn't mean it's spring yet though. It hurts people talking about that earlier. It is hard to believe it's March but keep in mind our winter weather lasts well in the March sometimes in April. If you're from Wisconsin you shouldn't ever be surprised what the weather is like, ever, ever, ever, ever. So what happened this winter? Why aren't we seeing that? We were supposed to have like this mega El Niño this year. They've been calling it like the Godzilla of all El Niños. So here I'm thinking as an El Niño guy I'm thinking we're gonna have a lot more snowfall, a lot more instead of that just a little bit more than average, we're gonna have a lot more than average because of this and we're probably gonna be, I wouldn't say much warmer than average but maybe even a little bit cooler because of the possibility of this jet stream being tugged so far down to the south so often it's gonna bring such that many more colder arctic or colder polar air blasts into our region. Well not really. The effects of it were, of El Niño this year were actually pretty minimal and it was actually predicted. I didn't read this until recently when I started to prepare for the presentation I'm gonna say a month ago but it was more like yesterday just kidding but I've had this presentation for a long time but I really didn't look into the effects on this winter as much until just a few days ago but they had predicted this months back. They predicted that yeah we're gonna be, there's a 60% chance in Wisconsin that your temperatures are gonna be on average higher than average and precipitation you're gonna have about a 40% chance that you're gonna have less precipitation than normal which doesn't jive with your typical El Niño results here in the Midwest. Typically we have a little bit more snowfall than average. The problem is El Niño is not the only thing that influences our winter weather. There are other climatic oscillations out there. A few of them. There's actually more than just these three but these are the big players. The way that all the stars lined up if you're into astrology you're gonna love that analogy but the way that the stars all lined up this particular year, the conditions of these different oscillation, the phases all came to be that the likely pattern was gonna keep basically keep the different atmospheric circulations from being as such that would give us more precipitation than normal. The temperature prediction was there but the typical pattern of El Niño winter is having more precipitation in the upper part of the country didn't happen and again it was mostly because of the state, the current state of these three different oscillations but there are other things that go along with it as well. Soil moisture, the amount of water and the soils for instance. Was it a summer or two? We had a pretty dry summer and that can have actually long lasting effects for many years after both winter and summer weather patterns but other longer term trends like lake temperature for instance of all the great lakes. We know a couple, a few years ago we had that extremely cold winter that was not a result of any La Niña or El Niño or anything like that. It just was more of a result of these other types of variables that go into forecasting but the effects of the colder lake temperatures from just a couple or three years ago are still having longer term kind of wave-like effects throughout our region especially during the winter months. So all these things put together basically outweighed the effects of El Niño this particular winter for our part of the country. Normally El Niño is one of the stronger variables that determines your seasonal outlook but this year it was not. So if anybody asks and they say, well these El Niño guys you know what they're talking about you gotta say, well look there's other things that go into our winter weather predictions and this year by chance these other things that came together their signals were strong enough to kind of outweigh the effects of El Niño. So that's what we have. We did certainly got our typical temperature warmer temperatures than normal but why is that? Why do we get warmer temperatures up here during El Niño? Think about the amount of humidity I talked about that's pumped into the atmosphere and as I said earlier the water vapor not only is just water droplets floating around the air it actually holds energy. Water has an extremely, it has a great capability of holding energy and heat. So the more water vapor the more humidity is in the air the warmer generally it's gonna be and this is especially important during our winters when we're normally a very dry atmosphere that's why it's so cold. When you're a lot more humid than normal the temperatures aren't gonna be as biting cold. We're still cold I mean we're in Wisconsin we have cold winters but not nearly as bad as we normally have cause the amount of increased water vapor humidity in the atmosphere. Okay I will play this guy for you and I'll show you where we're at right now with El Niño. Oh he lost my settings. No we didn't, okay good. All right this is what's currently going on right now. The colors underneath are showing the anomalies or the departures from the average of sea surface temperatures. This yellowish glow along the equator here in the central and eastern part you can see that in the eastern part of the Equatorial Pacific now there's pretty much warmer than average still yes and less warmer than average but still warmer than average in the central part. And as you can see these lines that are moving are actually the directions of the ocean current. Don't be fooled they're not moving that fast. It's just an animation to show you the kind of general flow and pattern of the ocean currents in this area. And this is normal but thing is during El Niño we usually see not as much of a nice what's the word I'm looking for? You don't see such a nice and neat flow of east to west. Usually you see the lines kind of going spreading a little bit north and south and not being nearly and these lines not being nearly as long meaning that the flow is not very organized. The water sits more stagnant than has a nice current pattern during El Niño's. So what this is indicating is that we're actually starting to get out of the current El Niño that we're in right now and as predicted what they predicted is by a right around the end of this winter this El Niño is gonna die down and go back to more normal conditions and possibly lead into a La Niña in the months to come whether it be a few months or a year or so we can pretty much expect some La Niña conditions of start and by looking at the organization of these ocean currents being so well uniform east and west uniform was the word I was looking for. You can see the more uniform flow going east to west this starts to indicate that we're going back to normal conditions and as you can see the sea surface temperature anomalies in this region aren't and you see some reds up in you know north and south of the equator but in the right around the equator itself is where you see that sea surface temperature patterns developing whether it be an El Niño or back to normal conditions or into La Niña conditions this is where you see it happening so this lighter yellow and I don't have the legend up but this lighter yellow indicates a little bit warmer than average but not much you're approaching pretty much average temperatures now for this time of year so what we're looking at is we're pretty much we're leaving our El Niño and going back to normal conditions now I could show a few more variables on here actually real quick before we get out of here maybe show surface wind patterns here let's go air let's go surface winds there we go okay good now this is showing our surface winds in this region and this is perfect because it shows the subtropical high right here right okay so it's showing it's kind of weak right now but you can see this southern flank of it is put the southern flank of the subtropical high surface winds flow east to west sort of pushing you know the east to west flow of this region right whereas the western or the pardon me the northern flank of it is what drives the what the east to west pardon me the west to east flow over the North American continent over the continental United States but the organization of these of this of this the directional flow of the surface winds now is also indicative of coming back to normal conditions where normally if it was still pretty strong El Nino conditions you wouldn't see such a nice kind of pattern coming out of the north east going southwest like this the again the patterns would be more or less all over the place and not very uniform as far as their geographic patterns okay I went a lot longer than I thought that's what we do I'm sorry instructors are terrible like that all right concluding remarks real quick okay as I said earlier it's El Nino is not a storm it's a climate system almost entirely of itself it's a coupled climate system it relies heavily on what's going on in the ocean namely the sea surface temperatures controlled largely by the depth of the thermocline below we have known about El Nino for a long time since the 1500s Peruvian fishermen told us all about it so this isn't something that a lot of times you hear like with because of global warming we have this thing called El Nino no that's not true this has always been around we're just starting to really understand it especially the second half of the 1900s of the second half of the 20th century is where we really started getting a lot more data collected again with anything with atmospheric sciences and weather prediction the more data you have the more accurate predictions are gonna be people complain about the weathermen all the time they get paid so much for not knowing what they talk about well I'll tell you what for not having a whole lot of data to work with in their models I think they do a pretty darn good job of at least getting us right around about what temperature we're gonna be at and generally getting right whether or not it's gonna rain maybe not the snowfall amount says much but they certainly if they say it's gonna snow generally it does if it's gonna rain generally it does so I think they do a pretty good job considering they only have a half a century is worth of good data or so before that not much and you think and you know now we take all sorts of atmospheric readings from humidity and wind direction and wind speed and everything else that we have every second whereas before we would just have oh a few times a day we take these things so think about that okay and again El Nino and La Nina are not complete opposites El Nino is more of a relaxation of a normal condition whereas La Nina is more of a amplification of the normal conditions and again they're not a flip-flop you're talking about a seesaw that never really flips over to the other side you're talking like a half seesaw here that's about it so as far as the conclusions with how this affects the United States weather the warmer the sea surface temperatures are the more it's gonna strengthen our subtropical high the more that subtropical high is strengthened the farther south it's gonna pull our jet stream and our jet stream again is that boundary basically between the warm air to the south the cold air to the north and this is where all the storm action is so over that jet stream average position is you're gonna have a lot of higher precipitation amounts around that region you're also gonna have cooler temperatures if it's pulled farther south especially in the southern U.S. where it's normally pretty warm just the opposite during La Nina La Nina expands that subtropical high so it keeps the jet stream farther north and that allows all that warm tropical air to push well up into the southern part of the U.S. and up into our midsection as you remember from that one map so you can expect much warmer and drier conditions at the south during La Nina and much, not much cooler but certainly cooler and much wetter conditions in the south during El Nino when the jet streams pulled farther south and again this year's Godzilla it's mostly the effects of El Nina were not nearly as pronounced as normal due to the other various type of climatic oscillation systems that we have that really do have quite an effect on our winters for the reasons of those all coming together in the proper proportions kinda diluted the effects of El Nino for us this winter especially us here in the northern part of the country questions, comments, concerns or complaints?