1. Understanding & Predicting Weather Conditions
Understanding and
predicting weather
conditions

2. Four Elements of Weather
This ELEMENT measures
heat in the air
TEMPERATURE
This ELEMENT measures
water vapor in the air
HUMIDITY
This ELEMENT measures
the force of air pressing down
AIR PRESSURE
This ELEMENT measures
the speed of air moving
WIND

3. Weather Tools
Thermometer
Anemometer
A thermometer measures the amount of heat in the air in degrees
A barometer
measures the weight of the air
An anemometer measures the velocity or speed of air movement in miles or kilometers
A rain gauge measures the levels or amount of precipitation in inches or cm.
Rain Gauge
Barometer

4. WIND Wind is caused by the uneven heating of the air.
Air moves from places of high pressure to one of low pressure.
Wind is measured by an anemometer. It is measured in miles per hour.
Wind direction is determined using weather vane.

5. Temperature Temperature is a measure of the amount of heat in the air.
Determined by how fast the molecules in the air are moving. The faster the molecules move, the warmer the temperature is.
Temperature is measured using a thermometer. It is measured in degrees.

6. Air Pressure
Refers to the weight of the air pushing down on the surface below.
LOW PRESSURE signals stormy weather.
HIIGH PRESSURE signals clear conditions.

7. Humidity Humidity is the measure of water vapor in the air.
Water vapor is water
that has evaporated
after being heated
Warmer climates have higher
humidity.
Why do you think this happens?
Chances of precipitation
Increase as the humidity does. Why do you think this happens?
Hygrometer

8. Water Cycle
The only way that Earth can be continually supplied with fresh water. The heat from the sun is the most important part of the water cycle.
This heat soaks up water from the oceans, lakes, rivers, trees and plants in a process called evaporation.
As the water mixes with the air it forms water vapor. As the air cools, the water vapor forms clouds. This is called condensation.
Most of the water is immediately returned to the seas by rain. The rest of the water vapor is carried inside clouds by wind over land where it rains or snows.
Rain and melted snow is brought back to the oceans by rivers, streams, and run-off from glaciers and water underground. This is the process of collection.
NOW IT STARTS AGAIN

9. Steps of Water Cycle
Evaporation:   Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.
Do plants sweat?
Well, sort of.... people perspire (sweat) and plants transpire.  Transpiration is the process by which plants lose water out of their leaves.  Transpiration gives evaporation a bit of a hand in getting the water vapor back up into the air.

10. Steps of Water Cycle
Condensation:    Water vapor in the air
gets cold and changes back into liquid. 
This is called condensation.
Precipitation:  Precipitation occurs when so much water has condensed that the air cannot hold it anymore.  The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

11. Steps of Water Cycle
Collection:  When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on land.  When it ends up on land, it will either soak into the earth and become part of the “ground water” that plants and animals use to drink or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts
all over again.

12. Precipitation Forms
When snow falls it is below freezing in the upper and lower levels of the atmosphere as well as on the ground
When sleet falls it is warm in the upper atmosphere, but dips below freezing near the ground forming icy pellets
When rain falls warms up as the icy crystals fall from the clouds (melting them), and stays warm all the way to the ground
When hail falls, it is warm at the upper levels and then turns colder. Updrafts cause water droplets to be lifted and cooled, forming chunks of ice. This can happen in a thunderstorm.
or sleet

14. CLOUDS

15. Cloud Group Cloud Height Cloud Types
Cloud Chart   
Cloud Group
Cloud Height
Cloud Types
High Clouds = Cirrus
Above 18,000 feet
Cirrus Cirrostratus Cirrocumulus
Middle Clouds = Alto
6,500 feet to 18,000 feet
Altostratus Altocumulus
Low Clouds = Stratus
Up to 6,500 feet
Stratus Stratocumulus Nimbostratus
Clouds with Vertical Growth
Cumulus Cumulonimbus
Special Clouds
Mammatus Lenticular Fog Contrails

16. CIRRUS CLOUDS Most common high cloud. Thin, feathery clouds
Associated with fair weather
Indicate rain or snow in the
hours ahead

17. Stratus Uniform, smooth grayish low clouds
Cover entire sky, blocking direct sunlight
resemble fog that doesn't reach the ground
Stratus
Thick blankets of cloud which produce light rainfall.

18. Cumulus Clouds Fluffy and white Flat bottom
Form from warm, moist air rising rapidly
through a cooler layer
Usually predict FAIR WEATHER until…..
they get larger and darker in the bottom

19. Nimbocumulus Clouds Could hold as much as 110,000 tons of water!
THUNDERCLOUDS
Largest of all clouds
Dark, threatening clouds
Often produce thunder and lightning
Can reach heights of
11 miles!

20. FIRST
NEXT
WARM FRONT
LAST
THIRD

21. FRONTS and changing weather
Boundary between two air masses of different temperature and humidity.

22. moisture to form clouds
Thunderstorms
storm with lightning and thunder.
produced by a cumulonimbus cloud,
usually gusty winds,
heavy rain and
sometimes hail.
Needs moisture,
unstable air and lift.
moisture to form clouds
and rain,
unstable warm air
that can rise rapidly.
Finally… lift.
from fronts,
sea breezes
or mountains.

23. Hurricanes

24. Violently rotating column of air that descends from a thunderstorm.
No other weather phenomenon can match the fury and destructive power of tornadoes.
They can destroy large buildings and lift 20-ton railroad cars from their tracks.
Tornadoes

25. FORECASTING

26. FORECASTING
Weather forecasting involves the observers and meteorologists and the work of  machines.
Computers make forecasts more accurate, and weather satellites orbiting the earth take photographs of clouds from space.
Forecasters use these observations from ground and space, along with formulas and rules based on experience of what has happened in the past, and then make their forecast.