3. What is the percent cloud
cover at the station?
What is the wind speed in
knots?
What direction is the wind
coming FROM?
What direction is it going to?
This funny looking thing is a weather symbol. It represents data recorded from a
weather station.
The circle is cloud cover.
The “tail” is the wind direction.
The feathers are the wind speed in knots. (1 knot = 1.15 miles)
0%
15 knots
NW
SE
4. • 1) Draw a weather symbol with
– ½ cloud cover
– wind at 5 knots out of the northeast.
5. • 2) Draw a weather symbol with
– 60% cloud cover
– wind out of the west at 55 knots.
6. What is a weather system?
• Remember the rule of thumb.
• Wind flows from areas of high to low
pressure!
7. • Air pressure is equal to the weight of a column of air
at a particular location. It is measured in millibars
(mb)
• High pressure systems are regions of relatively high
pressure.
– They are associated with dry weather and clear skies. Why?
- Air flows from high to low
pressure. Air sinks and flows
away from a high pressure
system. Therefore, few or no
clouds form.
8. • Low pressure systems are areas of relatively
low pressure. They are associated with clouds
and precipitation. Why?
Air flows from high to low
pressure. Air flows toward a
low pressure system and
rises. Therefore, many
clouds form.
9. What are fronts?
• An air mass is a large body of air with similar temperature,
pressure, and humidity throughout.
• A “front” is a boundary between air masses.
• We talk about “warm fronts” and “cold fronts.” These both
happen with low pressure systems. Why can’t they occur in
high pressure systems?
Air flows from high to low pressure. Air sinks and
flows away from a high pressure system.
Therefore, few or no clouds form.
10. Cold Fronts
– A cold front is a boundary between an advancing
cold air mass and a warm air mass that is already
present.
– It is represented by triangles that point the
direction the front is moving.
– Precipitation/clouds occur behind the front.
– Why?
11. • Cold air is more dense and “pushes” the
less dense warm air up. Clouds form and
precipitation occurs behind the cold
front. (I.e. it gets cold before it rains).
13. Warm Fronts
A warm front is a boundary between an
advancing warm air mass and a cold air mass
that is already present.
It is represented by semi-circles that point the
direction the front is moving.
Precipitation/clouds occur ahead of the front.
Why?
14. • Warm air is less dense and rises
above the cold air. It condenses and
forms clouds ahead of the front.
15. Brings cold air
Clouds and precipitation
behind the front Clouds and precipitation
ahead of the front
Brings warm air
Brings a weather
change.
Occurs during a
low pressure
system.
Cold Front
Warm Front
