How Weather Works

And it was a really cool experience to actually get to walk around and see the various people who work on weather science and try to figure out what was the weather doing right now and was it going to do next. I even managed to cause some problems for

the Weather Channel, but that wasn't entirely my fault. Uh Now to explain us, the Weather Channel and the Weather Company used to be the same entity, but then IBM acquired the product and technology divisions of the Weather Company and they bought those sections, but they didn't buy the television broadcast business. So now they are two independent businesses. One of them is run by IBM, the other one is its own standalone weather broadcast service. That being said,

they still work very closely together. The Weather Channel still gets a lot of its data and it's information from uh, the Weather Company, so it's not like they are completely independent of each other, and they both still exist in the same building. They both are located out of the

same headquarters building here in Atlanta, Georgia. So there is a Weather Channel studio that is in part of this building, and there's the Weather Company offices that's on different floors of the building, and UH they kind of co occupy space even though they are no longer corporately speaking anyway the same entity. So I thought it'd be fun to

do an episode about meteorology and weather models. This is gonna be a two part episode because I have to cover the science behind weather first and then talk about meteorology to let you understand how meteorologists base their forecasts off of weather conditions. You have to understand the complexities of whether before you can really get a grip on

what it is that meteorologists do. And so in order to do that, this episode is gonna be a little less about tech and more about science in order for us to have a deeper understanding of meteorology. In the next episode, I should I should also mention We've covered this topic in Tangential Ways and Older Tech Stuff episodes, but it was more than overdue for a revisit. So that's why we're going to talk about it today. We're

gonna really look at how weather systems actually work. Uh. And before I get too far, I guess I should actually explain what I meant when I said I caused some problems for the Weather Channel. So while I was at their headquarters, I was getting ready to shoot a video interview with a man named Dale Eck, who is the director of the Weather Forecast Center for the Weather Company.

So this guy is the head meteorologist in charge. He's been doing work in meteorology for thirty years, and he has a desk that's very close to the broadcast studio for the Weather Channel. The broadcast studio has glass walls, so you can see right through the walls. If you ever watch a broadcast on the Weather Channel and they shoot from inside the studio, you'll see people walking in

the background. You'll see desks and monitors and lots of of colorful imagery because people have got a lot of weather maps up in the background, so all of that's real. Those are the actual people who work at the company. Uh, and that's where we were shooting our videos. We were shooting off to one side of this studio, and while we're getting ready to shoot, we had set up the camera. I was miked. We had a shotgun mike so that

we can pick up Mr X his his contributions. We were off to one side of the studio, so we're up against where the glass walls are, but we weren't directly across from where the cameras were set up. Um, they did have sets where they could pivot around where we would have essentially been in the background for those those shots if they had set something up, but they were mostly shooting directly against the back wall of the

studio and we were on one of the sidewalls. So we're getting ready to shoot, and one of the the employees over at the Weather Company very helpfully pointed out a bank of light switches that were in control of production lights. So flipping those switches would turn several lights on in the area we were standing in That would end up providing a lot more light for our video, and that is really important if you're shooting video, you need good lighting. So after being told about them, we

turned them on. We being my producer, turned them on, and you know, he was essentially told to do it, so that's what he did. And it didn't take very long before a floor manager for the Weather Channel, very calmly walked up and asked us to knock that off. Although I should say she was incredibly friendly and professional. She wasn't mean about it at all, but explained that the light that we had created was bleeding into the set.

You know, it's a glass wall, lights just passing right through it, so it was affecting the shot for the actual Weather Channel, you know, the nationally televised Weather Channel broadcast. So my little YouTube video that I was shooting was impacting a nationally broadcast television scene. So that was a little bit of a Oopsie Daisy moment for me and my team. The nice thing is it was probably pretty subtle and it probably didn't have that big of an impact at all, but still it made us feel like

we were kind of jerk faces. And if you were watching the Weather Channel last week or this would that would have been, um, you know, this is June right now, so it would have been June Thursday. If you were watching the Weather Channel, you know, trying to keep up to date with Tropical Storm Cindy, and you were wondering, why is the lighting going all crazy in this broadcast? That was us are bad, But I have to really thank everyone who works for the Weather Channel and the

Weather Company. They were very generous with their time and they gave us lots of leeway to shoot really cool video. So it was a great visit and it helped me appreciate the complexities of meteorology on a deeper level. So let's now talk about weather forecasting. It's an interesting business. At a very very high level, like a super simplistic level.

Weather forecasting, at least in the recent past, involved taking lots of observations, comparing those observations of present conditions to things that had happened before in the past, researching what followed those similar conditions when they did happen before, and then making a guess as to what is going to

happen next based upon past experience. That's a drastic oversimplification, and really it's saying that it's about pattern recognition, and like, let's say, if you notice that when the temperature goes up at a certain time of day, with these other factors in place, the chance of rain increases drastically based upon past experience. You might use that to help forecast the weather and say there's a good chance that's going to rain later today because these other factors are at play,

and other times when that has happened, it's rained. But let me give you a more simple example about how this might work out. Let's say you've got some basic meteorological gear, like some sensors, a barometer, wind speed, indicator, wind direction. You know how much humidity is in the air. You know the temperature because you've got a thermometer, all these sort of things. These are the typical sensors you

would find at a weather observation point. You've kept a log book of weather for this particular location that goes back two decades, so you've got twenty years of information at your disposal, twenty years of collections of data points

and what was actually happening with the weather. You make your observation in the morning, you note the temperature, the air pressure, You've got all these different factors, and then you look at your log books and you look for days that are similar to the conditions you are currently observing. Then you look to see what happened later on those

previous days. So if you had one hundred mornings that are similar to the conditions of the morning you are concerned with, like this morning, you wake up, this morning, you take readings, you find one other, one other examples in your log book that are similar to today, and then you notice that on seventy of those one days it rained. You could say there's a seventy chance of rain. That seventy of the time, when conditions were the way

they are right now, it rained. Of those days where the conditions were exactly the way they are right now, it did not rain. And I don't really mean exactly. I guess I should say approximately, because weather is incredibly complicated and to have two weather systems behave exactly the same way under the same circumstances is pretty unlikely. But this, again is a drastic oversimplification of how weather forecasts work.

It does give you a basic idea of the the principle behind meteorological forecasts, at least until more recently we get into weather simulation and huge amounts of data processing. Today that gets a lot more sophisticated than just what are the conditions today and what happened on previous occasions when those conditions were present. But keep in mind meteorology

is constantly evolving. It has ever reached a perfect level status, as anyone who has depended upon a weather forecast knows, you've probably in the past looked at a weather forecast and said, oh, there's no chance of rain, and then a thunderstorm pops up. Well, that's because weather is really complicated and sometimes a hyper local event can occur that is impossible to really predict when you're looking at, say a regional weather forecast, because your fidelity doesn't get that small.

You can't predict everything that happens within that region with perfect accuracy. You're giving more of an overall look for the region as a whole. So it gets really complex. There are a lot of different variables, and there's a lot of different technology that goes into gathering the information about those variables and then crunching those numbers to make some meaning out of it, which is why it's an

ideal topic or text stuff. Now, if we are to understand really how meteorology works, we've we've got to take a deep looking at a look at whether or not a deep looking that makes no sense, but a deep look at whether. We at least need to get as deep in understanding for whether as we can in a casual podcast setting. So the first step is acknowledging the

difference between weather and climate. This is important because I see these two concepts conflated all the time, and frequently it pops up in in political discussions because you have people with agendas who want to push specific action items that favor their philosophy over the action items of people who oppose their philosophy. And frequently in those discussions, people will start to make generalizations about weather and climate that are,

if not untrue, at least inaccurate. So let's settle that. And I know all of you know this, but it's good to at least start with the baseline. So whether refers to the current state of the atmosphere, it's it's timely. It's either something that's happening right now, like you're talking about the weather right now, you're talking about a weather forecast. You're talking about something that's going to happen within the next day to ten days maybe or maybe a little

further out, but that's about it. Or you're talking about what has happened over the past few days, but that's about it. Like it's about a month or so of time stretching backward and forward uh in total from where you are right now, So it's very timely. Climate, however, is about whether patterns over vast spans of time or at least several years, if not decades of time. So climate is more about general weather patterns and how they behave over these these uh the span of years. So

climate change is very gradual. That means that you're not likely to notice climate change on a day to day basis, which means that if you use an argument like global warming isn't real because it's snowed last winter, that's a fallacious argument because you're talking there about whether not climate climate would be a gradual change, which over the course of several years might mean that after several years it's snowing less and less, or the snow is not lasting

very long, the the period of time where it does snow is decreasing, like it's becoming more concentrated in a narrower span of days. Those are the sort of things we might see as a result of climate change over the course of several years. But we humans aren't very good at conceptualizing that. We tend to focus on stuff that we've recently observed, but particularly when it's something that's

happening at at times. So if you were to have an unusually mild summer, you might think, well, that says that climate change is is bogus because I should it should be much hotter than that. That's not taking into account the long term changes in trends. So again, climate is the long view, whether is what is happening right now?

Now that we've established that, we can get past those weird straw man arguments people make that tried to discredit one another for whatever philosophy they have using weather in place of climate, it just doesn't work. Climate change, by the way, is a real thing. Uh, it is a scientific consensus has found that climate change is real and that humans have had an impact, a significant impact on climate change. And consensus is no small matter getting scientists

to agree to some thing. That's I mean, science is all about questioning claims and putting them to the test. That's how science works is you make an observation or you make a prediction, and then you test it over and over and over again to see if it holds true. If you get to a scientific consensus where a lot of scientists, the vast majority of them all agree on something, that's a powerful statement, although we often will see that dismissed. Uh So, again, this isn't to get political. This is

just stating a scientific fact, not a political effect. Climate change is real, humans have an impact on it. What does that mean politically, Well, that's a totally different discussion. So there's probably people out there who wish that climate change wasn't a real thing, that this was all just a manufactured story. But if wishes were horses, beggars would ride. As my old social studies teacher would say, So, climate describes weather trends over many, many years, and weather describes

changing atmospheric conditions on a much shorter time span. And our atmosphere is where weather happens. Again, not a big shock. This is elementary school science. It's made up of a lot of gases our atmosphere. The big one, of course, is nitrogen, that makes up about of the atmosphere. Then comes oxygen, which is my personal favorite. I'm totally breathless

without oxygen. It makes up about of the art's atmosphere, and then you've got less than a percent of argone point zero three carbon dioxide, and the rest of it is made up of small amounts of water, vapor, hydrogen, ozone, neon, helium, crypton, and xenon. Our atmosphere is pretty thick, and there's not really a hard barrier between the top of the atmosphere

in the beginning of space. It's kind of a fuzzy barrier, and there's not like you can't point to a specific height above the Earth and say, specifically, at this point the atmosphere ends, and this is just empty space beyond it.

The best you can do is do an estimation. So generally speaking, the atmosphere pretty much peters out into nothing once you reach about six hundred miles or one thousand kilometers above sea level, So you gotta go at sea level six d miles up and you're pretty much at the point where you're not going to find any molecules of any significant number that represent an atmosphere. Gravity holds the gases down to the planet, which I'm sure seems

pretty obvious. Without gravity, the atmosphere would dissipate into space, but don't worry, so would we. So the gases wouldn't be lonely for very long. It's a moot point because we do have gravity, so we're good. The atmosphere is also a very heavy thing. Collectively, if you take all of the other's atmosphere, it weighs five point five quadrillion uns. That's four point nine nine quadrillion metric tons. Again, that's collective.

That's all the atmosphere that surrounds our planet. Obviously, you are not walking around with a few quadrillion tons of weight on top of you. This weight of the atmosphere creates atmospheric pressure. The pressure is different at various altitudes, which makes sense. If you are on top of a mountain, you actually have less atmosphere above you, like there's less

air between you and outer space. If you're on top of a mountain, then if you were standing in the middle of a valley, there would be more air between you and outer space. Because again remember we're measuring that by sea level, so your altitude makes a big difference. You would have a lower atmospheric pressure at a high

altitude than you would somewhere with a low altitude. The pressure also compresses the gases in the atmosphere, so air closer to the surface of the planet is more dense than air that's near the edges of space, and all the weight above that low altitude air is forcing the various molecules to get all chummy with each other. So you've got denser air closer to the surface. So I've got more to say about atmospheric pressure and it's rolling weather in just a minute. But before I jump into that,

let me take a breath and thank our sponsor. All right, So let's say you are at sea level. The average atmospheric pressure at sea level is fourteen point seven pounds or six point seven kilograms per square inch. As you climb in altitude, the pressure and density of the air around you decreases until you reach a point where it would be quite difficult to breathe, and you need to breathe in more in order to get enough oxygen so

that you can continue, you know, living. So you might take a lungfull and not get enough oxygen to remain conscious if you're at a high enough altitude, which is part of the reason why mountain climbers have to tackle really tall mountains and stages. They have to have camps where they take a break and acclimate to the lower air pressure and lower air density of higher altitudes. So gravity obviously plays a big part in weather systems keeping

our atmosphere nice and in place. The Sun obviously also contributes to our weather patterns. The Sun is the direct source for most of the energy here on Earth. Some of the energy of the Sun gives off warms our atmosphere directly, but most atmospheric warming actually comes not from sunlight coming down to Earth, but rather the heat that is radiated off of Earth. The heat that the Earth has absorbed from the Sun. So the plant itself absorbs heat and then releases that heat later on. That tends

to be what heats up most of the atmosphere. The reason this happens is because the type of radiation that we're talking about radiation from the Sun is short wave radiation that easily passes through the gases the atmosphere and then it gets absorbed by the planet. When the planet emits heat, it's emitting long wave radiation. Long wave radiation gets absorbed readily by the atmosphere, so the atmosphere warms

from the ground up. And that also explains why if you were to climb a mountain as you would climb in elevation, the temperature would decrease to a point anyway in the troposphere. So there are four layers of Earth's atmosphere, and you classify those four layers by temperature ranges. The layers aren't uniform. Their thickness varies a bit as you go from region to region around the Earth, but they're

roughly outer shells of Earth. The innermost one is the atmosphere, as the level closest to the surface of the Earth. It ends somewhere around seven miles or eleven kilometers above sea level on average. Throughout the troposphere, as you climb altitudes, the temperature drops. That's one of the markers for the troposphere that all stops when you pass the tropo pause. That is the boundary between the troposphere and the stratosphere. That is the next layer out from the troposphere. The

tropospheres where all of Earth's weather happens. It also accounts for eighty percent of the air in our atmosphere. The other three layers contain the remaining twenty of the air in our atmosphere. Now, remember our atmosphere extends all the way up to six hundred miles above sea level, whereas the troposphere ends at seven miles above sea level. So within those first seven miles out of six hundred, you have eighty percent of the air in our atmosphere. That

tells you how densely packed those gases are. The stratosphere extends from the tropopause up to about thirty miles above sea level or forty eight kilometers. For the first few miles, the temperature of the stratosphere remains pretty stable with regards to the tropopause below. So remember you climb up through

the troposphere, the temperature starts to go down. When you hit the tropopause, the temperature pretty much stabilizes, and then you're in the stratosphere and the temperature remains stable for the first several miles, but then the temperatures actually start to increase. It starts to get warmer as you move through the stratosphere. This is because at those upper levels

of the stratosphere you can find ozone. Ozone can absorb ultra violet radiation from the Sun. Unlike most of the other gases, it actually can absorb some of those short wave radiations. So the ozone heats up, which means the upper levels of the stratosphere are also warmer than the lower levels. Above the amosphere is the miso sphere, where temperatures decline again, getting to be the coldest temperatures in Earth's atmosphere. Those temperatures hovered around minus degrees fahrenheit or

minus nineties celsius. And the final layer of the atmosphere is the thermosphere, which shares its outer body with space, and the air here is not dense at all. It's actually pretty widely spread out. The molecules are very thin like, it's very thinly populated, the opposite of very dense. In other words, the interesting thing here is that the thermosphere technically gets really freaking hot. We're talking like degrees fahrenheit

or shundred degrees celsius. But because those molecules are so few and far between, it would not feel hot to you because you wouldn't be in contact with these highly energized molecules. They're spread too far apart from each other. It's kind of like being inside and an enormous arena stadium and there are a dozen ping pong balls flying around. The Odds of any of those ping pong balls actually

making contact with you are pretty low. Because you're in a big area with these tiny things moving around, it's just not likely that you're gonna encounter one of them. Same thing is kind of true with molecules out in uh the the thermosphere. So while those molecules will be quite warm and you're not likely to run into them. Now back here on the surface, where we have the troposphere to deal with, you've got atmospheric pressure, you've got temperature.

These two factors affect atmospheric movement. As gases heat up, the molecules in those gases move around more, they spread out, they become less dense. When the density changes enough so that the air above is more dense than the air below, that denser air is going to sink down and displace the warm air that is there. You might have heard the phrase warm air rises, Well, it's true, but it's

really probably more accurate to say cold air sinks. If you were to have a very dense fluid and you put it on top of a less dense fluid, you'd see the dense fluids sink down to the bottom and the less dense fluid would rise to the top. Same thing is true with atmospheres and our atmosphere is a fluid, so these denser, colder areas sink down and that pushes the warm air up to the top. So this way you get some fluid movement in our atmosphere as different

areas start to warm up or cool down. Now, as that warm air does rise, it actually starts to cool down because it's going up in altitude. And remember and those altitudes in the troposphere. The higher you go, the cooler it gets. So the warm air initially gets pushed up by colder air, but then the warm hair itself

begins to cool and it has a tendency to sink again. Now, if everything we're equal, if our planet did not rotate, if we didn't have any uh variation in parts of the plant that warmed or cooled, if it all warmed or cooled at the same time, our atmosphere behavior would be really simple. It would expand when sun was hitting it, and it would contract when the sun wasn't hitting it. So you would just see the atmosphere kind of breathe that would move out and in based upon the warming

and cooling, and that's all it would do. You wouldn't get a whole lot of other movement there, but that's not our reality. The reality is we have a lot of other factors at play that create the the conditions

that allow wind to generate. So regions of the Earth warm at different rates at different speeds, and thus regions of our atmosphere end up warming at those different speeds, and that regional variation causes a lot of churning in the atmosphere, which creates pressure differentials between regions, thus leading to wind. So let's take a city and countryside example

to kind of understand what I mean by this. If you have a city, the city heats up faster than the countryside would during the day due to a lot of the materials in the city, you know, concrete, blacktop, these sort of materials soak up a lot of heat, so they're going to get much warmer than the countryside wood, which doesn't have those sort of materials all through it.

So you've probably heard of the island effect, which is where you get an island of heat because you've got a bunch of of mass that just absorbs heat readily in one space, and it creates an island effect within the region. That's what we're talking about here. The city ends up soaking up a lot of heat and then

releases that heat. Over the course of many hours. As cities radiate heat, that heat warms the atmosphere that's surrounding the city's That warm air is less dense than the cold air that's further on the outskirts of the city, out in the countryside, So the warm air is an area of low pressure because it's less dense. It's actually exerting less pressure on the city because it weighs less. It is less dense than the cold air that's around it, or the relatively cold air compared to the city's air.

So the cold air blows into the city because it wants to move from an area of high pressure to an area of low pressure, sort of that. In tropic movement, the warm air is forced upwards in an updraft and starts to climb up into the upper levels of the troposphere. As it does so, it starts to cool, and once it cools enough, it needs to come back down. But because cities soak up so much heat, and because the updraft can be so powerful, the cold air can't just

sink back down to where it was. It actually has to move outward and then sink down further out from where the city is. It's almost like a fountain. You would see the water of the fountain come up in a column and then spread out in a fan the top and come back down to the base of the fountain. That's sort of what's happening, except with atmosphere, not with water, although it could be with water. We'll get into rain

in just a second. So at night the city would cool faster than the countryside does, and then the trend would reverse itself. We would have winds that are originating essentially from the city moving out to the countryside. This little system is what we would call a convection cell, and convection is when the movement of mass or circulation of atmosphere transfers heat through some sort of substance. In this case, we're talking about the planet and the atmosphere.

On a larger scale, forces affect these movements to generate massive weather weather patterns. The poles are areas of high pressure and the equator is an area of low pressure. You've got a lot warmer air moist air in the equator, a lot cold or dry air over at the poles. And if that was all there were to it, we would see winds coming from the north and south and converging towards the equator. But there are a lot of other areas of high and low pressure across the surface

of the Earth. It's not just the polls and the equator. There's a lot of variation there due to tons of different stuff, including topography like mountains and valleys, that sort of thing, deserts. So you have lots of areas of high and low pressure across the surface of the Earth, which creates natural pressure gradients, and that generates wind. Wind from high pressure areas cycle inward to low pressure areas. In fact, we call a low pressure center a cyclone.

Now it's not the same thing as cyclones that are also known as hurricanes, slightly different, although there is a circular motion to it. That's where you get that cyclone name there. High pressure centers are anti cyclones, as an anti not as an anti cyclone the sister of my father, who we don't talk about. It's a different thing entirely. High pressure air moves in a down undraft as low pressure air moves in an updraft, and Earth's rotation also gets into the game. This is where we get the

Coriolis effect. In the northern hemisphere, wind deflects towards the right. In the southern hemisphere it's deflected to the left. The Coriolis effect really influences large fluid masses, by the way, so it does not necessarily affect which way the water goes down a sink or a toilet, despite what the Simpsons would have you believe. Uh, there are a lot of other smaller things that can affect the way water drains down the drain and is not the Coriolis effect.

Coriolis effect is really for very big systems, not for small systems like a a sink full of water or a tub full of water. But the Coriolis effect does break the two big convection cells that otherwise would exist, you know, the ones that would be the North and South hemispheres, and it ends up creating three different types of convection cells. You get two of each type. You have two polar cells to Hadley cells, and two Feral cells. And the Hadley and Feral cells are named after meteorologists

who discovered them. This is the important thing, really is to remember that these convection cells have a really big impact on on larger weather trends, global weather trends now where the wind blows down here near the surface, air encounters resistance in the form of friction, but a bit higher up in the atmosphere that's not a problem. So jet streams shoot around at fairly high altitudes we're talking twenty thoty five thou feet or between six and fourteen kilometers,

and they don't encounter this friction. They move it incredible speeds. They can carry temperature changes effectively around the world. So you'll see things about jet stream and how that will affect local weather patterns depending upon where you live. High altitude winds, the coreolas, affected pressure gradients are the three big influencers of wind generation on a global scale. But remember regional geography, coastlines, mountains, valleys, all of that also

has an effect. Regional heating and cooling has an effect. So these big factors are the major variables, but they're not the only ones. And now you're starting to see all the complications that come into just describing weather, let alone predicting it. But that covers wind. Rain is pretty easy to explain. The water cycle on Earth is pretty much a closed system. Water evaporates into the atmosphere. Water vapor condenses as it cools down, so it condenses from

water vapor and turns into liquid water. It starts to cling to specs of stuff in the atmosphere, little particles of dust. Uh. That ends up becoming the nucleic sites for rain drops. If it is able to accumulate enough water vapor. The cooling happens. Once water vapor rises high enough into the air, and with enough cooling water vapor, you get clouds. Wind will push and reshape the clouds,

moving them to different locations. And if you get enough water vapor condensing around those nucleic sites, it becomes too heavy to remain aloft by the winds alone, and it starts to fall. And that's when you get rain, or if it's really cold, you might get sleet or freezing rain or snow. But you get what I mean, you get precipitation. I've got a little bit more to say about the water cycle and other elements of weather, but before I jump into that, let's take another quick break

and thank our sponsor. So water vapor can be pushed into higher altitudes through several different ways. One of those

is just changes in elevation in the land. So if you have a warm air system and it's got a lot of water vapor in it, and it moves across flat lands and start to encounter mountains, it has to conform with the topography, so as it gets pushed against the mountain, it actually starts to go up the mountain, and that means some of that water vapor gets pushed up to higher elevations and it gets high enough, then it can cool down, condense, turn into clouds, and eventually

even turn into precipitation. So if you've ever heard about windward and leeward that's what this refers to. The windward side of a mountain is the side that faces the area where wind comes in from. So traditionally the direction front which fronts move through, so you have a warm air mass coming through to a hit a mountain, that's

the windward side. The leeward side tends to be gloomy and covered in rain a lot because that water vapor that hits the windward side gets forced upwards into the higher parts of the atmosphere or of the troposphere i should say, condenses into uh into clouds, and then eventually can turn into rain or precipitation of other forms, and on the leeward side that's where you get that rain, and you also have a lot of cloud cover. So there's a sunny side of a mountain and there's the

less sunny side of the mountain. Typically, and uh, that's one way water vapora can be pushed into high altitudes to form clouds. But there's also an way called frontal wedging, which originally I thought was something that happened to me back in middle school, but it turns out I was

thinking of something totally different. This is actually when warm air ends up colliding with a cold air mass, and the cold air mass sort sort of acts like a ramp because remember a cold air is more dense than warm air, so warm air is going to float above or rise over cold air. It ends up being wedged on top of cold air. That pushes warm water vapor up into those higher altitudes again where it can condense

and form clouds. So if you have a warm air mass moving into to a cold front, or rather a cold air mass, not a cold front, then this can happen. The warm air will rise over the cold air, the water vapor in the warm air will slowly condense and then you end up getting clouds as a result. This is typically what we call a front. So a warm front is when warm air moves into an area that has cold air in it. A cold front is when cold air moves into an area that has warm air

into it. So essentially it's a low pressure system moving into a high pressure system, or a high pressure system moving into a low pressure system. And then you've got these masses colliding with one another. Really, it just depends on what type of air mass is moving in and what type of air mass is currently in the region. That determines whether it's a cold front or a warm front. But then you also have two other types of fronts.

You have a stationary front, and these cases you have two air masses that are unable to advance against each other. They kind of just bump up against each other and stay there. And then you have the occluded front. This is when a cold front moves fast enough to overtake a moving warm front. So that's another way that water vapor can be pushed up into the higher elevations. Way number three for water vapor to go moved moving up

to those higher altitudes is called convergence. Now this is not the same type of convergence I typically like to talk about here on tech stuff. It's when two similar air masses collide and both end up forcing air into an updraft, which includes water vapor. And so yet again we see water vapor get pushed up and cooling down to condense. But that's convergence. And finally you have what

is called convective lifting. This is a localized effect, so it's not something that happens on regional or global scales, but rather very local scales. It's when Earth's radiation of heat causes a pocket of air to warm and rise, forcing water vapor up in the process and creating clouds. This requires having an area that is absorbing a lot more heat than its surroundings typically do. So a good

example might be a large airport. The airport's got a lot of surface area that gets exposure to the sun. It absorbs a lot of heat, much more heat than the surrounding area typically does, and so it releases more heat and as a result, you can get cloud formation above airports just because of this localized convective lifting. So now we understand the general principles behind weather that air pressure temperature and the presence of water vapor matter a lot.

Now other things matter too, of course. The Earth's access, for example, is that twenty three and a half degrees tilt, which means we're likely, uh, we're we're we're like, we're bobbling, bobbling around like a wobbly top as we orbit the Sun, and this causes different parts of the planet to receive more or less sun exposure during certain parts of the year. That ends up affecting weather patterns and seasonal patterns and weather. It's complicated in that incoming systems can have a dramatic

effect on systems that are already within a region. So it's an enormous, chaotic mess with lots of variables, and that's part of the reason why meteorology is so darned challenging. We cannot isolate those variables. We cannot really understand how to properly weight all of them in every situation. That is, determining which variables are most important under any given set

of circumstances, it's really really hard to do. So you might say that under a certain set of conditions, the temperature of the air is the most important variable, and that depending upon that temperature of the air, certain outcomes are almost absolutely gonna happen, right But then you might say, under slightly different circumstances, temperature no longer becomes the most important variable. Now it's air pressure that's more important than temperature.

Weather is so complicated, and there's so many different variables that have different weights and different situations that it becomes very, very difficult to understand what is happening right now, let alone predicting what is going to happen. In fact, I find it amazing that we can manage to have any real accuracy and weather predictions at all, because it's so

crazy complicated. Now, Before I wrap up, I thought it'd be fun to talk about some of the earlier forms of weather forecasting before you know, sensors and and observing stations and computer models came along. The stuff we used to do before we had all those sophisticated technologies and really a truly astonishing amount of processing power capable of

handling all those points of data simultaneously. Because we humans have been trying to suss out weather for centuries, knowing what the weather will be like has a tremendous impact on our decisions like should I buy tickets to that outdoor sporting event, or how can I plot a course for these shipping goods to get from point A to point B with the least amount of delay and fuel consumption.

But our methods for making predictions haven't always been terribly scientific, and it's heart a lot of our weather predictions were centered on pattern recognition. That's what I alluded to at the top of this episode. We would say, hey, remember that other day that was a lot like today. Well, it rained like a son of a gun later on the evening, and that other day, I bet that happens again tonight. I bet we get more rain tonight, because

that's what happened that other day. Early human civilizations made similar observations and predictions, which range from the immediate, which would involve something like I better seek shelter because it looks like it's going to storm, to more long term planning, such as I've noticed that the weather seems to get warmer for a while, and then everything is growing, and then after a while the weather starts getting cold and

everything stops growing. So maybe I should grow stuff in this one part of time and harvest stuff at this other part of time. In other words, we started learning

more about how seasons work. There are some changes in conditions that are a bit too subtle for humans to pick up on them by themselves, but they're are other animals that are more sensitive to those changes, things like atmospheric pressure, for example, and so humans would sometimes observe changes in animal behavior that would precede certain types of weather events. Those behaviors would become associated with weather, leading to some folk knowledge about what it means when your cow,

I don't know, switches from Xbox to PlayStation. I guess I should point out right now that I haven't been on a farm in like thirty years, so my understanding of animal behavior might be a little off. But those approaches don't really give you very much detail, nor are they useful outside of the immediate area. If you see your cows are playing Halo two instead of Uncharted, it doesn't tell you about the weather that's going on in the town on the other side of the valley, for example.

And let's say that you want to go to the other side of the valley because you need to sell your I don't know yearly parsnip harvest, So for that you would need more information. You would need someone on the other side of the valley sending you observations of their weather phenomena, and also a way of understanding what those observations mean in relation to that area's local weather.

You would need a meteorologist and some reliable data gathering sensors, and in our next episode will explore those worlds and talk about the complex models scientists have created to describe and predict our weather and to really get a grip on how impressive it is and why we need supercomputers to run some of these weather models. Will also talk about why are there more than one? Why is there more than one weather model? Wouldn't one weather model work

for everywhere? As it turns out new there are a lot of different weather models, and they all have different levels of resolution, meaning some of them have way more observing stations reporting in for a localized area, which means you have very very accurate reports of what is happening in a specific region, but they don't cover a large region, like a large area might be a section of a country, but not an entire country, or certainly not a continent.

Then you might have much larger weather models that cover continents, but they do so at a much lower resolution. You

don't have specific accuracy for independent regions. Ideally, what we want to arrive at is a global model that can have incredible resolution down to the local level, so that we know what the weather is going to be like in our hometown, we know what the weather is going to be like in the place we're going to travel to on the other side of the world, and we can even see how the weather conditions in one location are affecting the subsequent locations further down the line. That's ideal.

We are not there yet in our next episode. We'll talk about why that is. But for now, if you guys have suggestions for future episodes of tech Stuff, please let me know what those are, because I hate guessing. You can write me My address is tech stuff at how stuff works dot com, or you can drop me a line on Facebook or Twitter to handle at both of those is tech Stuff hs W. If you would like to watch me record an episode live, go to

twitch dot tv slash tech stuff. You can see the schedule there and you can join in and watch as we have technical difficulties that extend a forty five minute long recording session into an hour and a half that really happened today, and you wouldn't be able to see it unless you go to Twitch dot tv slash tech stuff to enjoy and watch as other people pop into

the studio and try and fix problems. It's exciting. I hope to see you there and I'll talk to you again really soon for more on this and thousands of other topics. Because it has staff works dot com