Winds

Question 1

High Pressure
Wind direction

Answer 1

Anticlockwise

Question 2

Low Pressure
Wind direction

Answer 2

Clockwise

Question 3

Coriolis Effect

Answer 3

• the faster moving object will push object (wind) out in front of where its going
• Equator is moving faster then poles

+ Winds from equator move East in front of spin direction
+ Winds from poles move West (not spinning as fast)

• Particles moving across a rotating surface - path it traces is deflected

Question 4

Pressure Gradient

Answer 4

The rate at which pressure changes over a given horizontal distance determines the Pressure Gradient

Greater pressure gradient
= faster moving air
= high winds

Question 5

What happens when a High Pressure is really close to a Low Pressure ?

Answer 5

A High wants to be a Low

Greater pressure gradient
= faster moving air
= high winds

high pressure air quickly moves to low pressure area

Question 6

High pressure & low pressure

In North
&
South Hemisphere

Answer 6

North
- Low Pressure = Anti-Clockwise
- Hight Pressure = Clockwise

South
- Low Pressure = Clockwise
- Hight Pressure = Anti-Clockwise

• A low is always in the direction of earths rotation
  + looking upwards on south pole - its rotation is clockwise
  + looking downwards on north pole - its rotation is anti-clockwise
• both cyclonic rotation

Question 7

Gradient Flow

Answer 7

Gradient flow = wind following Isobars around pressure system (clockwise or anti-clockwise

Wind behaviour = Coriolis effect & pressure gradient force

• If pressure gradient stronger = curves right in a low P system
  If Coriolis Effect stronger = flow curves left in High P system

Wind speed low = Stronger Pressure gradient force (goes out of high into a low)

Winds increase = Follows isobars more

Question 8

Geostrophic Flow

Answer 8

• Isobars are straight
• Exact balance between gradient flow & Coriolis flow
• Wind swings neither left or right

Question 9

Buy Ballot’s Law

Answer 9

If you stand with your back to the wind in the southern hemisphere, the low pressure will always be on the right

Question 10

If QNH at destination aerodrome is less than departure point where is wind coming from ?

Answer 10

Wind coming from RIGHT

Question 11

If QNH at destination aerodrome is same than departure point where is wind coming from ?

Answer 11

Flying along isobar
Wind either TAIL or HEAD wind

Question 12

What hight does Surface friction effect wind

Answer 12

below 3000 ft

Question 12

Direction of Surface Winds in southern hemisphere

Answer 12

Always to the right

wind in L pressure turns Right into Low
wind in H pressure turns Right into Low

Both deflected across Isobars into L Pressure system

Question 13

Near the surface what force on wind is stronger

Answer 13

Near surface = more friction = lower wind speed

Pressure Gradient stronger

Pulls winds across isobars
Veers RIGHT

Question 14

Backing wind =

Answer 14

BACKING to the LEFT

Question 15

Veering wind =

Answer 15

VEERING to the RIGHT

Question 16

how much does wind speed drop & direction Veer
Over Land =
Over Sea =

Answer 16

Over Land = 2/3 -> Veers 30’
Over Sea = 1/3 -> Veers 10’

Question 17

What is a Squall

Answer 17

• Wind Change by at least 16 kt
• Reach 22 kt or more
• Sustained for more then 1 min

Question 18

What is a Gust

Answer 18

Sudden change of smaller magnitude & duration
Rapid increase in wind strength followed by a lull back to average speed

Question 19

What is Wind Shear

Answer 19

• 2 adjacent airstreams - that don’t mix
• boundary of airstreams becomes turbulent

Could be different
+ Speeds
+ Directions
+ Temperatures

Question 20

Types of Wind Shear
&
When they occur

Answer 20

Horizontal -> up / down drafts in mature TS

Vertical -> surface inversions - cold surface air - hot air above

Question 21

Sea Breeze

Answer 21

1 ) Land heats during day (vs slow warming water)
2 ) Warm land air rises (creates L pressure)
3 ) Cool sea air comes onto land

• Strongest Mid afternoon

Question 22

Land Breeze

Answer 22

1 ) Land cools at night
2 ) Warm air over ocean rises (water slow to cool)
3 ) Air blows out to sea

• More gentle sea breeze
  (temp diff isn’t as great)

Question 23

Katabatibc winds

Answer 23

Conditions =
= Night
= Steep land descent
= Clear skies (allowing max land heat loss)
= Cool surface air & Warm surrounding air

• Air is denser & heavier then surrounding air
• Gravity down land = Strong winds
• Strongest at dawn

Question 24

Anabatic Winds

Answer 24

- During the day - Wind blows up sloping terrain - Weak winds (have to go up hill) - During Afternoons 1 ) Land heats 2 ) Warm air rises 3 ) Cool air bows up terrain to replace hot air

Question 25

Low Level Jet Streams

Answer 25

- Form in tropical inland areas E.g. - High Pressure system moves east across Aust - Lower level air is trapped between centre of H pressure & mountain ranges - Makes Isobars crowd together - Increases surface pressure gradient -> wind speed increases