How hurricanes and tropical cyclones are formed and named.
storms | Typical, everyday weather is important to watch and fun to keep track of. It is the weather we see most of the time and the type of weather and storms that has the greatest influence on our lives. Some of the real fun of observing weather happens when the weather gets a little bit crazy and even dangerous.
One of the most common types of violent weather is a thunderstorm or electrical storm. Thunderstorms can range in intensity from a really short and intense rain burst with some lightning and thunder to a full blown tornado.
Besides thunder and lightning, one of the defining characteristics of a thunderstorm is its intense winds, especially the vertical winds. A thunderstorm is generated when warm, moist air is blown upward. As the air rises towards the cooler higher altitudes it reaches the dew point and the moisture in the air begins to condense and form snow or raindrops.
As the drops collide and form bigger drops, they begin to fall. As the water drops fall, they will cause a localized cooling effect, which causes even more winds to blow.
When the different temperature air masses rub against each other they can build a static electrical charge. The molecules of air and water rubbing together set up an electrical imbalance just like when you scuff your stocking feet across a carpet. Usually, the top of the thundercloud is positively charged while the bottom is negatively charged, but sometimes the cloud moving over the ground can give the ground a negative charge.
When the total charge is big enough, the electrical structure of the atoms in the air between the two charges begins to break down or ionize. This ionized air is highly conductive, and what we see as lightning is the plasma energy created when the charge between the positive and negative zones equalizes.
The sudden increase of temperature and pressure along the lightning bolt causes a rapid expansion and contraction of air which we hear as thunder.
The most severe thunderstorms are called supercell thunderstorms, and they occur when the wind changes direction and speed at different heights, and there is a separation between the updraft and downdraft zones. Tornadoes are often associated with supercell storms.
The name tornado comes from the Spanish word for thunderstorm. The funnel cloud of a tornado is formed around a localized low-pressure zone. The condensation of moisture inside the funnel and the dust kicked up by the intense surface winds allow the funnel cloud to be visible.
The winds associated with most tornadoes are below 110 mph and the tornado may travel a few miles before dissipating. A severe tornado may have winds up to 300 mph and travel for dozens of miles.
Here is some interesting Trivia: The first time a Hollywood movie successfully used showed a tornado effect on screen was in The Wizard of Oz (1939). This was decades before digital effects and green screens were even considered, and the science of weather forecasting was still primitive enough that sending a crew out to Kansas in hopes of filming a real tornado was out of the question.
Special Effects director A. Arnold “Buddy” Gillespie attempted to use a water vortex and a rubber cone to fill in for his tornado, but the results were not realistic. Finally, he noticed that the windsock at the local airport was the shape he was looking for. He made a 30′ muslin sock which he hung from a crane over the set.
The bottom of the fabric cone was attached to a car below the stage floor, and compressed air hoses blew dust and wind into it to simulate the debris which swirls around the base of an actual tornado.
The Weather Channel named the tornado scene from The Wizard of Oz in their list of Great Moment in the history of weather. The scene inspired several generations of meteorologists to take up the science.
A hurricane is a type of tropical cyclone and is one of the largest and most intense storms on the planet. Tropical cyclone refers to where the storm forms, and its winds, which circle around a low-pressure center or eye. Cyclones in the Northern hemisphere turn counterclockwise and clockwise in the South. The storms are generally “born” over warm tropical oceans, but rarely within 5° of the equator.
Warm, moist winds blow radially toward the low-pressure area at the center of the storm, feeding it with more and more energy. A hurricane can grow to between 60 and 2,500 miles in diameter.
Hurricanes are such large weather events that they are traditionally given names. Names are generally selected in advance for each season and assigned in alphabetical order. Tropical cyclones which originate in the Atlantic are referred to as hurricanes and those which affect the Western Pacific region are called typhoons.
In case of Hurricanes or other extreme weather events, safety should be your first concern, therefore we recommend to prepare in advance. You could either prepare an emergency kit buying all the items one-by-one or use ready-made kits.
Q1: What are the defining characteristics of a thunderstorm?
Q2: What makes a tornado funnel cloud visible?
Q3: What gives a hurricane or typhoon its energy?
A1: Lightning, thunder, and intense winds
A2: What we see as a funnel cloud is the condensing moisture inside the low-pressure zone along with the dust and debris picked up by the intense winds.
A3: The storm gains energy and intensity as the low-pressure center travels over hundreds of miles of warm, open ocean water.
How humidity is the amount of water vapor in the air and relative humidity is the measurement of how much moisture is present versus how much moisture the air can hold in a certain temperature
How water changes its physical state from solid ice to liquid water to gaseous vapor depending on temperature.
That the changing state of water drives the water cycle and the water cycle drives the weather
How precipitation occurs when water vapor in the air condenses as the air reaches the dew point
Barometric or atmospheric pressure and how low-pressure air rises and high-pressure air sinks through the atmosphere.
Basic weather terms | If you sat down and listened to strangers meeting and getting to know each other, what would they be talking about?
Most of the time they will be talking about the weather because it is something that we all have in common. There is even an old joke that says “Everyone talks about the weather, but nobody does anything about it!”
When weather becomes subject to study or a hobby, it is good to understand the language that weather scientists, formally called meteorologists use. Meteorology seems like a very complex science, and it is because the weather is something that happens over the whole planet. However, the concepts that every meteorologist or weatherman uses are fairly simple to understand.
In the last section, we learned that water has three physical states, solid ice, liquid water and gaseous water vapor. Humidity is the presence of water vapor in the air. The mix of gases in normal air is usually around 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide, and varying amounts of other gases, including water vapor. The normal concentration of water vapor is about 1%, but air can hold more or less water vapor depending on its temperature.
Since air at specific temperatures can hold a certain amount of water, we can measure how much water vapor is in the air compared to how much the air can hold at that temperature. This is called relative humidity.
When the air can hold no more water vapor, we say that it is saturated, or 100% relative humidity. The lower the relative humidity is, the more readily liquid water will evaporate into it, and as water evaporates it takes heat energy with it. When warm air, which can hold a lot of moisture, cools, it may approach the dew point, which is the temperature where the water vapor begins to condense back into liquid.
This is what drives the water cycle, and the water cycle is what drives weather. In a simplified fashion, the cycle goes something like this:
As the sun heats the air over the ocean, the warmer air is able to hold more of the water vapor that evaporates from the surface of the water.
As the air warms, it also rises and cooler air moves in to take its place.
As the air rises it cools, and the cool air replacing the warm air causes winds to blow.
As the first mass of warm air rises, the winds may blow it over a land mass where it may cool to the point that it cannot hold the same amount of water vapor. The water condenses out of the air as clouds and eventually precipitation in the form of rain or snow that falls on the land, and runs down hill to lakes and rivers, eventually to the ocean and the cycle starts again.
Precipitate is a fancy word which means to fall.
When the air temperature drops below the dew point, the water vapor begins to condense into water droplets, and the water begins to give up the heat energy it absorbed during evaporation. When this happens up in the sky we see it as clouds, if it is at ground level it is fog or mist.
Mist and fog are classed with precipitation because they form like other types, but the water droplets are so small that they remain suspended in the air rather than falling.
Dew forms on objects on the ground that are at a temperature lower than the dew point of the air. If the object is below the freezing point of water, frost forms. When water vapor in clouds begins to condense, either on dust particles or simply into droplets, the same thing occurs. If the air in the cloud is below the freezing point, ice crystals form. As more water condenses and freezes, the crystal grows until it becomes a snowflake, and when the flake grows too heavy to be supported in the air, it falls to the ground.
Rain forms in two basic ways. The water droplets in a mist or fog collide with each other until they form a drop that is too big to remain suspended and it falls as rain, or a snowflake will go through a layer of warmer air as it is falling; and as the flake melts it becomes a rain drop. Sometimes in a thunderstorm, the flake may begin to fall and partially melt until the winds catch it and carry it higher where it takes on more water and freezes again.
This cycle continues until it is too heavy for the winds to carry back aloft and it falls as hail.
When we talked about water we mentioned the three states of matter, solids, liquids, and gases. Solids are, well, solid, they pretty much hold their shape. Liquids and gases are fluids, which means that they change their shape to suit whatever they are being held in. Gases are much less dense than solids or liquids, which means that there is more room between the molecules of a gas. This means that gas can be compressed, the molecules squeezed together.
Since there is already less room between the molecules of a liquid, a liquid cannot be compressed.
Imagine a cube of air on the ground next to your chair, a foot high, a foot deep and a foot long. Now imagine another cube of air the same size stacked on top of the first one. Once you have the second cube in your imagination, keep stacking the cubic feet of air on top of each other clear up to the sky.
Each cubic foot of air has weight, and they are all pressing down on the cubic foot of air at the bottom. This is called pressure, and it forces the molecules of the air closer together.
We know that a piece of wood is less dense than water and a rock will be denser, so the wood will rise to the top if you push it down into a bucket of water while the rock sinks to the bottom. In the atmosphere, air with greater density (higher pressure) sinks while less dense (low pressure) air rises. If there is an area of high pressure over your house, you can expect generally fair weather.
A low pressure, however, generally indicates stormy weather. This is because as the air rises through the atmosphere it cools rapidly to the dew point where the moisture in the air gives up the energy it gained during evaporation, and that energy is what drives a storm.
We think that temperature is a measure of how hot or cold something is, but that does not tell the whole story. How hot or cold something is an expression of how much heat energy is present, with more energy the molecules move around and run into each other more.
As the energy increases, so does the temperature, and as energy is given up, the temperature falls, but only to a certain point. We know that at sea level, water freezes at 32°F. That means that the water is giving up energy as the temperature falls, but at 32°F the liquid water still has too much energy to freeze solid. The water needs to give off the excess energy to the surrounding air before it can change its physical state.
You can demonstrate this by putting a clean glass of water in the freezer for a couple of hours. If you time it just right you can take the glass out of the freezer with the water still in liquid form, but when you give the glass a little shake crystals begin to form and the water freezes into slush. Before it freezes, the water is said to be “supercooled”.
Sometimes you get “superheated” water from a microwave oven, which can be a dangerous situation. When the temperature of water at sea level approaches 212°F the temperature stops rising as the water absorbs enough heat energy to change its physical state from liquid to gas.
Sometimes when you heat water in the microwave using a clean, smooth glass or cup the temperature of the water may exceed the boiling point. As soon as to give the cup a small shake, it suddenly boils which can cause a nasty burn.
Temperature is commonly expressed using either the Fahrenheit scale or the Celsius scale, which can get a little confusing. Most scientists and people in other countries use Celsius, but the weatherman on your local TV station and most of the people you know use Fahrenheit.
Sometimes when you are watching a news report from overseas you may hear the reporter say that it is 22°C, and you are not sure if that means it is hot or cold.
Tip: Most people need a conversion chart or a calculator to convert between the two scales, but here is an easy way to do it in your head. This method is not completely accurate, but it is close enough that you can understand temperature in a conversation.
When you hear a temperature in Celsius, simple double the figure in your head and add 30. The actual conversion formula is to multiply by 1.8 and add 32, but rounding will get you close enough.
In this example, 2 x 22°C = 44, add 30 and we get 74°F. If we had used the formula and a calculator we would have gotten 71.6, but either way we can tell that it is a nice day.
Q1: What is 100% Humidity?
Q2: What is “the dew point”?
Q3: How does hail form?
Q4: What do we call the weight of air forcing air molecules closer together?
Q5: How hot is it if you hear that the temperature in Sydney, Australia, is 18°C?
A1: At 100% relative humidity, the air is “saturated” and unable to absorb any more moisture through evaporation.
A2: When the temperature of the air falls to the point that the moisture in the air begins to condense, it is said to be at the Dew Point.
A3: When air rises into the cooler upper atmosphere, the moisture reaches the dew point and begins to condense into tiny droplets of water. As the temperature continues to drop, the droplets form ice crystals, on which more moisture condenses. When the crystals become too heavy, they begin to fall as snow, and may begin to melt. In a thunderstorm, the partially melted flakes can be blown higher where they refreeze and absorb more condensing moisture. After several falling, melting and refreezing cycles they finally fall as hail.
A4: Barometric Pressure
A5: For a quick estimate, 2 x 18 = 36, add 30 and we see that it is about 66°F in Sydney, so it is a nice day. For a more accurate conversion, 1.8 x 18 + 32 = 64.4°F, so 66 degrees is close enough for most things.
How weather is what is happening in the atmosphere
The difference between climate and weather
How heat from the Sun is the energy that drives weather
Introducing how moisture in the air absorbs and releases energy
Every day before you go outside you probably take a look out the window to see what the weather is doing. Most people are happy if it will be sunny and warm so they can put on shorts and play in the backyard, and if it is rainy and cold they would rather stay indoors with a warm drink.
It is easy to think of weather as simply being nasty or nice, but there is a lot more going on than just these two opposites. Weather is what is happening in the atmosphere at a particular place, and the weather is always changing.
There is weather inside your house as well and we will be looking more closely at the inside weather to help us understand how the weather outside works.The climate is in the news a lot these days. Climate and weather are related, but they are not the same thing, and it is hard to understand climate until you understand weather.
Weather is what is happening in the atmosphere at a certain time at a certain spot while climate is a study of the weather in an area over a long period of time.
Looking out the window seems pretty simple, we see that it is either sunny or cloudy, windy or calm. In fact, many different things influence what the weather is doing in your backyard. Some of them are hundreds or thousands of miles away from where you are. The two most important things that affect the weather are heat and moisture.
The heat comes from the Sun shining on the Earth. Since the Earth is tilted relative to the Sun, the area around the Equator receives more heat than at the poles. Also, the Earth is spinning, so the everywhere that the Sun is shining now will be in darkness in a few hours.
In general, warmer air rises and cooler air comes in to replace it. The new air warms and the cycle continues. It’s like putting a big pot of water on the stove to boil; the water in the bottom of the pot near the middle gets hot first because it is closest to the fire. We can see the water in the pot begin to circulate in a process called convection.
As the hottest water in the bottom of the pot moves up, it cools a little bit and the cooler water moves to the bottom and begins to absorb the heat from the element. When all of the water in the pot becomes so hot that it cannot absorb any more heat, it boils.
The heat from the Sun is the energy that drives the weather, just like gasoline is the energy that drives a car. Just a tank full of gas will not make a car move, of course. It needs an engine to convert the energy of the gasoline into motion. The engine in the atmosphere that drives the weather is water, or more specifically moisture.
You may have been taught that water exists in three states of matter: solid, liquid, and gas in the forms of ice, water and vapor or steam.
We are told that water changes between these states according to temperature: water below 32°F occurs as frozen ice, between 32°F and 212°F water is liquid and above it is steam. However, there is another factor that is just as important as temperature to determine the physical state of water; pressure.
Let’s go back to our pot on the stove. What if we went outside and filled the pot with snow?
As soon as we brought the pot inside the ice in the snow begins to melt, and it melts even faster when we put it on the stove. Not only does it get hotter from the element, but the convection we saw in the boiling water is circulating to help the snow melt faster. Remember that convection it is the transfer of heat through the movement of particles; warm particles rise, cool particles fill in the space below.
The convection will continue until the liquid water boils and becomes steam unless we put a heavy lid on the pot. If the lid is heavy enough and seals the pot so that no steam can escape, there is too much pressure for the water to boil, and the liquid water can be hotter than 212°F. The opposite occurs when the pressure is low. At high altitudes, water boils at a lower temperature.
We will look at temperature, pressure and moisture a lot closer in the next section.
For now, just keep in mind that everything we see as weather exists because of three things, heat energy from the Sun, air moving because of temperature differences, and more or less moisture in the air because of temperature and pressure.
Q1: What provides the heat energy that drives weather?
Q2: What causes the air in the atmosphere to move?
Q3: What are the three physical states of water?
Q4: What are the three basic elements of weather?
Q5: What provides the heat energy that drives weather?
A1: The Sun
A2: Differences in temperature cause the air to move. Warm air tends to rise and cooler air that sinks rushes in to replace it.
A3: Solid ice, liquid water and gaseous vapor.
A4: Heat from the sun, temperature differences in the atmosphere, and moisture in the air.
Learn how kids can learn to love the planet by learning how weather works
Learn how we can learn about weather and how it works
Learn basic safety measures to take in case of dangerous weather
Teach kids about weather | One of the greatest things about being a parent is discovering the world through their young eyes. How many common things have become extraordinary when you share them with your kids? They are even more special when they are something that they can share with you.
It is never too early to begin teaching your kids to love the planet they were born on. And the best way to love it is to learn about it. There are any number of ways to do this, a trip to the zoo or aquarium, a camping trip in the woods, a hike in the local park, all are great ways to introduce the wonder and majesty of nature to a young mind.
But the opportunities are not as easy to find as we would like. These things take planning and preparation, but the weather is always there, just outside our windows.
In fact, there is weather inside the house as well, and we will study that as well so that we can understand what is going on in the sky outside. Eventually, we will be able to see how a dust storm on the other side of the planet influences whether or not you will have a White Christmas.
But our main focus will be why is it sunny one day and stormy the next, what is really going on when snow or rain is falling, even why it can be raining at home but sunny at school!
This is a good time to begin thinking about weather and storm safety.
Storms that bring thunder, lightning and even tornadoes can be frightening for small children, but understanding why teach kids about weather and why it is doing what is doing can take away some of the scariness. It does not make the storms less dangerous, but being less frightened, kids are less likely to make mistakes.
We will learn more about specific weather safety hazards as we go along, but here are some important safety tips to keep in mind now:
Always be aware of the weather. Of course, you should always take a look through the window before you go outside to see if you need a jacket or coat, but take the time to check the forecast, either from TV or radio, online, or from your home weather station, to see if the weather could get worse.
If the dangerous weather is predicted, it does not mean that it will happen but know the signs so you can watch for them. If the sky suddenly fills with dark clouds and it starts to rain, seek shelter. Not only will you be more comfortable, you will be safe from lightning or tornadoes.
The best place to be is in a building or a car with the windows rolled up. Avoid exposed shelters like metal sheds, baseball dugouts, bleachers, or under a lone tree.
If there is lightning in the area and you cannot find shelter, crouch down in an open area, at least twice as far away from the nearest tree as it is high, and cover your ears to prevent hearing damage from thunder.
Stay away from water and metal. Both will conduct electricity and may attract a lightning strike.
If there is tornado danger, remember to D.U.C.K. – “duck” :
Get DOWN to the lowest level of the building,
Get UNDER something solid like a table or a desk,
COVER your head to protect from falling debris,
And KEEP inside the shelter until you are sure the danger has passed.
Q1: Why is it important to understand “inside weather”?
A1: The processes that occur in the atmosphere inside a building are the same as happen outside. If we can learn what is going on in the small scale, it is easier to understand what is happening on the larger scale of the outdoors.
Q2: What is the safest place to be in a sudden storm?
A2: Seek shelter in a building or in a car with the window rolled up.
Q3: How do you D.U.C.K. from a tornado?
A3: Get DOWN to the lowest level of the building, get UNDER something solid, COVER your head, and KEEP inside until you are sure the danger has passed.