1. A Skill For Outdoors People
Predicting Weather
A Skill For Outdoors People

2. Weather
Weather simply refers to the condition of the air on earth at a given place and time - whether it is warm or cold, dry or wet, blowing or calm.  The condition of air and how it acts to create weather is influenced primarily by two things:
Heat (the sun)
Water

3. Sun’s Influence on the Weather
Weather on earth starts with the sun.  The sun's heat warms our atmosphere and causes two things to happen:
water evaporates into the air
air rises

4. Precipitation
As air rises, its temperature drops.  As the moisture in the air cools, it condenses into tiny suspended droplets, forming clouds.  The droplets inside the clouds become larger as more moisture is evaporated into the air.  Eventually, they are too heavy to remain suspended and fall to earth as precipitation - rain, snow, sleet or hail.

5. Air Pressure & Weather Maps Maps
Weather maps show the positions of air masses. An air mass is a very large body of air that has similar properties. Air masses move, so they can be tracked over time. They are clues to the future temperature, moisture level and air pressure of the area into which they are moving.
How is air pressure measured, and plotted on a Map?

6. Weather Maps Show Air Pressure
Winds move Anti-Clock Wise around a high
Winds move Clock Wise around a Low H L
The Closer together the Isobars the stronger the winds.

7. Colliding Air Masses
When one air mass meets another, the air in different masses usually does not mix because the properties of the air are different. A boundary, or front, forms between the two air masses. Stormy weather often occurs along fronts.

8. Cold Fronts
A cold front forms where a cold air mass moves into a warm air mass. Cold air contracts, becomes more dense, and thus heavier than warm air, so the cold air pushes underneath the warm air. Cumulus clouds and showers or thunderstorms may be scattered along cold fronts. As the front passes, the wind changes direction. Skies begin to clear, and the temperature usually drops.

9. Pressure Systems, Wind & Clouds
Cold front Cloud with cool SW winds behind it.
High Cirrus Cloud ahead of Cold Front
Clouds spiralling clockwise around the low pressure
Rain can occur under the influence of a high pressure when it pumps moist winds off the ocean like here in Qld.
Clear stable conditions under the high pressure

10. Using Pressure Systems to Predict the Weather
Certain weather conditions are associated with high and low pressure systems.
Knowing the characteristics of these systems can help you predict the weather.
Lets take a look at a high and low pressure system and determine what each would look like if we were in the field on a trip.

11. High Pressure
High pressure areas, or highs, are shown by "H" symbols. In a high pressure system, air pressure is greater than the surrounding areas. This difference in air pressure results in wind, or moving air. In a high pressure area, air is more dense than in areas of lower pressure. The result is that air will move from the high pressure area to an area of less density, or lower pressure. Winds blow away from high pressure areas toward areas having lower air pressure.
High Pressure

12. Low Pressure
Low pressure areas, or lows, are shown by "L" symbols. Winds tend to blow into low pressure areas because air, like other gases, moves from areas of higher pressure into areas of lower pressure. As winds blow into a low, the air moves up. This upward flow of air can cause clouds and precipitation to form.
Low Pressure

13. Measuring Air Pressure
Air pressure is measured by barometers.  In general, weather will improve when pressure increases and worsen when pressure decreases.

14. High Pressure Characteristics
Stable descending air mass
Calm winds
Often see fog or frost
Clear skies
In Australia winds from NE area.
Clear day above, fog in the valleys, under high pressure influence.

15. Low Pressure Characteristics
Unstable ascending air mass.
Winds increasing
Increasing cloud cover
As the low approaches in Australia, temperatures increase.
Winds swing to NW ahead of change.
High cirrus cloud, with increasing NE then NW winds, with increasing temperatures are a sign of approaching low pressure.

16. What Would We See in Perth
Winds flowing anti-Clock wise around the high.
As the cold front approaches winds swinging to the NW & strengthening. Closer together isobars = stronger winds.
High Cirrus then stratus cloud increasing
What the sky would look like in Perth

17. Knowing What Conditions Clouds Form Under Can Help You Predict Changing Weather

18. Early Signs In The Sky For Approaching Bad Weather
High Cirrus Cloud = Bad Weather on the way!

19. Hot Days with Unstable Air = Cumulus Nimbus Clouds & Thunder Storms
Classic Anvil of a Cumulus Cloud
Storm Cells taken from a Satellite
Begin To Worry
Run for Cover
If you see these clouds developing, think storm. Have a plan for shelter.

20. Cumulus Storm Clouds & Precipitation
Lightning is our biggest threat when in the outdoors in storms!

21. Lightning: Our biggest threat to safety when in the outdoors during a storm.

23. Precautions against Lightning Strikes

24. The weather is dynamic. You must be prepared for all conditions.

25. Always be prepared for the worst!

26. Monitoring the Weather in the Field
To complete the class we will now attempt to identify the weather in different parts of the country.
The map on the following slide identifies a town or city in Australia. You have to identify the wind direction, cloud type, and temperature estimate solely from looking at the weather map.
Your teacher will click on the hyper link to get the answers! Good luck.

27. Test Your Weather Skills What is the Weather at…
Test Your Weather Skills What is the Weather at…? Click on the town for the answer!
Class, discuss the forecast for each place; then Click on the City for the answer
Kalgoorlie
Perth
Melbourne

28. Monitoring the Weather on Solo
Later this term you will be required to monitor the weather for the three days of your solo experience.
You will then have to make a forecast as to what you think the weather will do based on your observations.
You will need to monitor: Wind, clouds, temperatures, precipitation.
The following sheet is a copy of the one you will fill out on solo.
Let us attempt to fill it out for today’s conditions.

30. The End

31. Perth Hot Conditions Winds Strengthening out of the North West
Increasing cloud cover, most likely High Cirrus (1), descending to alto-stratus (2) as the front approaches. 1 2
Click to return to Map

32. Kalgoorlie Clear Skies Stable Conditions
Dew on grass first thing in morning
Light but warm to hot northerly winds
Click to return to Map

33. Melbourne Cold Front and Low Pressure over city Unstable conditions
Cumulus Clouds
Possible storms & rain
Warm to hot early, temperatures dropping after front has passed
Winds turning fresh to strong from the Southwest
Click to return to Map