Created by Mrs. Susan Dennison 2015-2015
The atmosphere is a layer of invisible gas (air) that surrounds the Earth. It wraps around the planet like a blanket.
All weather happens in the lower atmosphere.
What causes weather? Winds keep our atmosphere in motion (moving). Air moves in masses. Winds push those masses around. All weather gets its start in the atmosphere. We can often predict the movement of those air masses and therefore know what weather may come our way. Scientists who study the weather are called meteorologists.
How is weather different from climate? Weather: what conditions of the atmosphere are over a short period of time Climate: how the atmosphere "behaves" over relatively long periods of time
A meteorologist is a scientist who collects data about the weather and uses it to make predictions, or forecasts.
People who study meteorology depend on special instruments to help them understand what has happened and to forecast what will happen.
A thermometer is the device that measures the temperature (amount of thermal, or heat energy) of the air and tells us how hot or cold it is in degrees. 17 C 62 F Degrees in Celsius *Most of Europe and the rest of the world use this system. Degrees in Fahrenheit *This is a system we most commonly see in the U.S.
The two scales used to measure temperature are named after their inventors who lived in the early 1700s. Fahrenheit Celsius Fresh water freezes at 32 F Fresh water freezes at 0 C Human body is 98.6 F Human body is 37 C Water boils at 212 F Water boils at 100 C
Anemometers are instruments that measure wind speed and sometimes direction.
Wind or weather vanes are instruments that tell from which direction (n,s,e,w) the wind is blowing.
Barometers are instruments that measure air pressure the weight of the atmosphere. The dial has numbers and sometimes pictures of a cloud or sunshine. The HIGHER the air pressure, the drier the weather is likely to be. The LOWER the air pressure, the nastier the weather is likely to be.
Air pressure is the force caused by the weight of the air pushing on things. The wind blows from areas of high pressure (high means heavier ) towards areas of low pressure ( less pressure ). Warm air rises and cool air sinks towards the ground. HIGH PRESSURE = happy weather LOW PRESSURE= less happy weather
Rain gauges are instruments that measure the amount of rain that has fallen. Rain falls into a large cylinder that has measurement markings on the side.
Hygrometers are instruments that measure the amount of humidity, or moisture, there is in the air. When it is humid, we usually feel sticky and our hair gets frizzy. If it is hot, we feel icky. *Higher numbers show more moisture. The air is more wet.
Satellites are machines that scientists also use to keep an eye on our weather. They hover over our Earth and send information and pictures back to groups like The National Oceanic and Atmospheric Administration (NOAA).
Where do clouds come from? 1. Water evaporates. 2. The air becomes full of water vapor (clouds are condensing water vapor). 3. Air currents rise. 4. Water vapor condenses and falls as water droplets or frozen precipitation (rain, sleet, snow, hail).
Clouds are made of billions of tiny droplets of water formed around specks of dust in the air. Fog is a cloud close to the ground. There are many types of clouds.
Cirrus clouds are feathery and usually are seen on fair (good) weather days.
Cumulus clouds are fluffy, white clouds with flat bottoms. The billow out, change shape, and even look like familiar shapes or cotton balls. The usually indicate fair (good) weather.
Stratus clouds are smooth and gray. They cover the whole sky, like a gray blanket, and block direct sunlight. They usually indicate light rain, drizzle, or snow (if it is cold enough).
Cumulonimbus clouds are big, stacked, and darker on the bottom. Cumulo-nimbus is Latin for heap rain. They usually indicate downpours of rain, hail, lightning, high winds, and sometimes even tornadoes!
Precipitation: hail, rain, sleet, and snow In Virginia, we are most likely to see hail and rain during the summer. It does not have to be cold outside for us to see hail!
Precipitation: hail, rain, sleet, and snow When rain and snow are mixed, we experience sleet, which is slushy. We see this when temperatures are just slightly above freezing and rain or snow is in the forecast.
Precipitation: hail, rain, sleet, and snow If both the air temperature in the clouds and the atmosphere is below freezing, we will experience snow, or frozen precipitation.
Dew forms when warm, moist air cools down causing water to condense. Ever notice dewy grass on a foggy morning?
If there is a lot of water vapor in the air, meteorologists tell us that it is very humid outside. When there is a lot of humidity, many of us feel icky and sticky, especially if it is also hot outside!
What else can tell a meteorologist that wild weather is in our future? Areas where high pressure is about to collide with low pressure are called fronts. They can often bring wild weather and are trouble spots.
When a cold air mass is cutting under a warm air mass and lifting it, it is called a cold front. Its symbol on a weather map looks similar to icicles and is usually depicted in blue.
If a warm air mass is rising up over a cold air mass, it is called a warm front. It looks like half a sunrise on a weather map and is usually depicted in red.
What other symbols are used on a weather map? There is a lot of useful information on a weather map. For example, a big, blue H shows high pressure systems that will bring cool, dry air and light winds. Low pressure systems will be shown with a big, red L. They bring swirling masses of warmer air that is moist. Stormy and windy weather is often on its way.
By reading the map legend of a weather map, you can also see warnings of snow, possible thunderstorms, floods, and other dangerous conditions. You can better prepare yourself for the weather to come.
Hazardous, or dangerous weather conditions include things that could cause harm or damage. We need to prepare for things like thunderstorms with lightning, hurricanes, and tornadoes.
Thunderstorms are often characterized by loud rumblings, called thunder, and bright displays of lightning. Lightning is nature s static electricity, and it is very powerful. Thunderstorms can cause tornadoes, hail, flash flooding, strong winds, and even wild fires!
Three things are needed to make a thunderstorm: 1. Moisture 2. Unstable air 3. A lifting source
Hurricanes are huge, slow-moving storms that are fueled by heat and energy from warm ocean waters. They always form over large bodies of water.
Hurricanes that blow over the warm Pacific Ocean currents are called by another name, typhoons. Ones that blow over the Indian Ocean are called cyclones.
Hurricanes can cause storm surges, wind damage, and severe flooding. They are named after people. In 2005, Hurricane Katrina s storm surge brought terrible destruction to the southern U.S. coast.
Tornadoes, also called twisters, are dangerous, funnel-shaped columns of air that reach from a thundercloud to the ground. There is usually a warm air temperature. They have winds that spin dangerously fast.
Tornadoes can be extremely dangerous and more difficult to predict than other storms. These strong storms can also bring giant hailstones and torrents of rain.
A tornado s spinning winds form a vortex that pulls up at the center of a storm. The vortex is a mass of spinning air.
Weather Conditions Day Air Temperature ( F) Air Pressure Day 1 25 F low Day 2 80 F low Day 3 30 F high Day 4 65 F high According to the data table above, on which day will there most likely be a thunderstorm with heavy rain? 1. We know that there will be snow, not rain, if the temperature is well below freezing. 2. We know that high pressure indicates fair, or good weather. Low pressure indicates poor weather. Day 2 is the day we can expect thunderstorms and heavy rain. A warm front has come in and the air pressure is low.