19. Polar Front Depression Part 2

Question 1

Polar Front Depression Pt 2

Refer to the following diagram. Numbered in order is the cloud formation with the passing of a polar front depression. What are each of the cloud types;

1. [ ]
2. [ ]
3. [ ]
4. [ ]
5. [ ]
6. [ ]
7. [ ]
8. [ ]
9. [ ]
10. [ ]

Answer 1

1. [Ci]
2. [As]
3. [Ns]
4. [St Fra]
5. [St / Sc]
6. [Ns]
7. [Emb Cb]
8. [As]
9. [Ci]
10. [Cu]

COMPLETED

1

Question 2

Polar Front Depression Pt 2

1. The slope ratio of a warm front is 1:80 or 1:150
2. The slope ratio of a cold front is 1:80 or 1:150

Answer 2

1. 1:150
2. 1:80

• REMEMBER warmer temperatures have higher degrees celcius
• Think of the slope ratios as temperatures, 80 and 150
• The warmer temperature (warm front) is 150, and the colder temperature (cold front) is 80

POLAR DEPRESSION

1

Question 3

Polar Front Depression Pt 2

In the continuous moderate rain just ahead of the warm front, what type of cloud formation might form at the low level

Answer 3

FRACTOSTRATUS
(StFra)

POLAR DEPRESSION

1

Question 4

Polar Front Depression Pt 2

At which point of a polar depression might you expect drizzle followed by continuous rain, possibly snow

[ ] 500 nm ahead of the warm front
[ ] 100 nm ahead of the warm front
[ ] At the warm front
[ ] Within the warm sector
[ ] At the cold front
[ ] 200 nm behind the cold front

Answer 4

[ ] 500 nm ahead of the warm front
[X] 100 nm ahead of the warm front
[ ] At the warm front
[ ] Within the warm sector
[ ] At the cold front
[ ] 200 nm behind the cold front

• Just ahead of the warm front
• Stable mTw is cooling on the colder air below

POLAR DEPRESSION

Question 5

Polar Front Depression Pt 2

At which point of a polar depression might you expect heavy showers;

[ ] 500 nm ahead of the warm front
[ ] 100 nm ahead of the warm front
[ ] At the warm front
[ ] Within the warm sector
[ ] At the cold front
[ ] 200 nm behind the cold front

Answer 5

[ ] 500 nm ahead of the warm front
[ ] 100 nm ahead of the warm front
[ ] At the warm front
[ ] Within the warm sector
[X] At the cold front
[ ] 200 nm behind the cold front

• The cold front lifts warmer mTw air up
• This is convective lifting and NimboStratus clouds form as well as Embeded Cumulonimbus
• These bring heavy showers, and occur at the “nose” of the cold front

POLAR DEPRESSION

2

Question 6

Polar Front Depression Pt 2

At which point of a polar depression might you expect advection fog in winter;

[ ] 500 nm ahead of the warm front
[ ] 100 nm ahead of the warm front
[ ] At the warm front
[ ] Within the warm sector
[ ] At the cold front
[ ] 200 nm behind the cold front

Answer 6

[ ] 500 nm ahead of the warm front
[ ] 100 nm ahead of the warm front
[X] At the warm front
[ ] Within the warm sector
[ ] At the cold front
[ ] 200 nm behind the cold front

• As the warm front approaches the ground is moist from precipitation and cold
• The air mass within the warm sector is mTw, so air is warm and moist
• The air is warmer and cooling so bringing on the onset of the dew point
• Advection fog in winter can be expected, and within the warm sector stratus cloud

POLAR DEPRESSION

2

Question 7

Polar Front Depression Pt 2

1. Wind speeds within the warm sector of a polar front depression are FASTER or SLOWER than the wind speeds within the cold air ahead of the warm front
2. Wind speeds within teh warm sector of a polar front depression are FASTER or SLOWER than the wind speeds within the cold air behind the cold front

Answer 7

1. SLOWER
2. SLOWER

• In both cases, the wind within the warm sector is slower than the wind speeds within the cold and cool sectors
• We know that wind speeds in High pressure systems, also associated with warmer air, are slower
• Inlow pressure systems, the gradient wind is stronger and the isobars bend in towards the low
• Therefore in teh colder sectors, whcih are associated with the low pressure system, the wind speeds are greater

PRESSURE AND WIND SPEEDS

3

Question 8

Polar Front Depression Pt 2

Refer to the following diagram. Completed each of the missing fields for WIND;

WIND
1. [ ]
2. [ ]
3. [ ]
4. [ ]
5. [ ]

=====

WIND
* VEERS
* VEERS
* W
* NW
* SW

Answer 8

1. [SW]
2. [VEERS]
3. [W]
4. [VEERS]
5. [NW]

COMPLETED

3

Question 9

Polar Front Depression Pt 2

Refer to the following diagram. Completed each of the missing fields for PRESSURE;

PRESSURE
1. [ ]
2. [ ]
3. [ ]
4. [ ]
5. [ ]

====

PRESSURE
* FALLING
* FALLS
* STEADY
* RISING
* -

Answer 9

1. [FALLING]
2. [-]
3. [STEADY]
4. [FALLS]
5. [RISING]

NOTE
* There is an exam question where it asks what will happen to pressure at point D in 1 hour
* Remember that the point itself is NOT MOVING with the passing of the front, but is stationary
* This is not clear in the question and it is meant to be inferred that the point is stationary
* Therefore, after 1 hour, the pressure will increase as point D is in effect in the position that point E is at in an hours time.

COMPLETED

3

Question 10

Polar Front Depression Pt 2

Refer to the following diagram. Completed each of the missing fields for TEMPERATURE;

TEMPERATURE
1. [ ]
2. [ ]
3. [ ]
4. [ ]
5. [ ]

=====

TEMPERATURE
* STEADY WARM
* STEADY, COOL
* STEADY, COOL
* FALLS
* INCREASES

Answer 10

1. [STEADY, COOL]
2. [INCREASES]
3. [STEADY, WARM]
4. [FALLS]
5. [STEADY, COOL]

COMPLETED

3

Question 11

Polar Front Depression Pt 2

Warm Fronts

1. Warm fronts on average move at ____kts
2. Radiational cooling at night cerates cool dense surface air behind the front. This will inhibit what 2 things
3. The average width of a precipitation zone on a warm front is ____ miles (____km)
4. Turbulence is typically STRONG or WEAK apart from the frontal layer where it will be MODERATE or MODERATE TO STRONG
5. Severe icing can be anticipated in Nimbostratus if temperatures are around ____℃ to ____℃
6. The transition zone depicted on the surface of a weather chart as a line with red semicircles is a band ____ to ____ miles wide

Answer 11

1. 10 KTS
2. LIFTING and FORWARD PROGRESS
3. 185 Miles (300 KM)
4. WEAK / MODERATE TO STRONG
5. -7℃ to -10℃
6. 30 to 60 miles

POLAR FRONT DEPRESSION

4

Question 12

Polar Front Depression Pt 2

Cold Fronts;

1. The transition zone depicted on the surface of a weather chart as a line with blue triangles is a band ____ to ____ miles wide
2. Active cold fronts (slow moving) average speed of ____ kts
3. Inactive cold fronts (fast moving) have an average speed of ____kts
4. Given an equal pressure gradient, the rate of movement of a cold front is ____% greater than that of a warm front
5. The cloud mass is around ____ miles wide
6. In winter, cloud types will usually be ____ and ____
7. In summer, cloud types will be ____
8. Icing and turbulence associated with thunderstorms, especially in summer, will be ____

Answer 12

1. 30 to 60 miles
2. 15 kts
3. 25 kts
4. 50%
5. 120 miles
6. NIMBOSTRATUS and ALTOSTRATUS
7. EMBEDDED CUMULONIMBUS
8. SEVERE

POLAR FRONT DEPRESSION

5

Question 13

Polar Front Depression Pt 2

Warm Sectors;

1. Consists of a ____ air mass
2. What might be expected in coastal regions in winter
3. Visibility is typically ____ at best, with it possibly being poor in winter

Answer 13

1. TROPICAL MARITIME
2. FOG
3. MODERATE

POLAR FRONT DEPRESSION

6

Question 14

Polar Front Depression Pt 2

1. The high level wind (jet stream) associated with a polar front depression when viewed from above on a weather chart, will be BEHIND or INFRONT of and CLOSE TO or FAR FROM from the cold front line.
2. The high level wind (jet stream) associated with a polar front depression when viewed from above on a weather chart, will be BEHIND or INFRONT of and CLOSE TO or FAR FROM from the warm front line.

Answer 14

1. BEHIND / CLOSE TO
2. INFRONT / FAR FROM

• When seen from above the jetstream appears to be situated in the cold air ahead of the warm front and behind front
• In reality, we have to remember that the fronts are sloped, and as such, the jetstream is actually in the warm sector aloft
• Compare the overhead view to the side profile view below
• The reason the jetstream is clsoer to the cold front is that the gradient of the slope is steeper

JET STREAM & POLAR FRONT DEPRESSION

JET STREAM SIDE PROFILE

Question 15

Polar Front Depression Pt 2

1. When a warm front crosses over a mountain range, it is possible for warm air to get trapped on the UPSTREAM or LEESIDE of the mountain
2. When a cold front crosses a mountain, precipitation and fully developed clouds are anticipated on the UPSTREAM or LEESIDE of the mountain

Answer 15

1. UPSTREAM
2. UPSTREAM

• As he warm front crosses the mountain, some warm air can get trapped on the windward (upstream) side of the mountain
• When the cold front approaches, the trapped warm air is forced upwards as a result of both orographic lifting and the cold air forcing its way underneath the warm air
• The warm air will want to rise as it is lighter than the cold air
• As a result, this triggers lifting and convective cloud formation and intensive presipitation

Question 16

Polar Front Depression Pt 2

1. The area associated with the rain ice triangle and most severe danger of icing is COLD or WARM air AHEAD or BEHIND the warm front
2. The best means to escape the rain ice triangle is to DESCEND or CLIMB (excluding the option to perform a 180° turn)
3. What icing will be associated with flying into the ice triangle

Answer 16

1. COLD AIR / AHEAD OF WARM FRONT
2. CLIMB
3. RIME & CLEAR ICING

• The ice triagnle occurs when the aircraft is flying below the warm front in temperatures less than 0℃
• The rain falling from the warm front is in temperatures just above 0℃ When it falls into the cold air, it becomes supercooled
• On contact with the aircraft, icing occurs.
• The warmer air just ahead of the aircraft will have a higher level 0℃ so it is advised to fly up
• Flying down may put the aircraft into warmer air but may put you very close to the ground

ICING

Question 17

Polar Front Depression Pt 2

When the cold front catches up with the warm front, this will become an occluded front;

1. If the air behind the occlusion is colder, this will form a COLD or WARM occlusion
2. If the air behidn the occlusion is cooler, this will form a COLD or WARM occlusion

Answer 17

1. COLD
2. WARM

OCCLUDED FRONT

10

Question 18

Polar Front Depression Pt 2

A warm occlusion;

1. At the surface will take the shape of the WARM or COLD front
2. Precipiation will fall AHEAD or AT THE SURFACE of the occlusion at surface level
3. Over North West Europe, warm occlusions are common in WINTER or SUMMER
4. The cloud aloft is likely to be Cb or Emb Cb

Answer 18

1. WARM FRONT
2. AHEAD
3. WINTER
4. Emb Cb

• Over NW Europe, warm occlusions are common in Winter as the aldn tot he east is cold and the sea to the west is warm
• Remember that the polar air is blowing from a NE direction, and the sub tropical air from the SW

WARM OCCLUSION

11

Question 19

Polar Front Depression Pt 2

A cold occlusion;

1. At the surface will take the shape of the WARM or COLD front
2. Precipitation will fall AHEAD or AT THE SURFACE of the occlusion at surface level
3. Over North West Europe, warm occlusions are common in WINTER or SUMMER
4. The cloud aloft is likely to be Cb or Emb Cb

Answer 19

1. COLD FRONT
2. AT THE SURFACE
3. SUMMER
4. Cb

• Over NW Europe cold occlusions are common in summer because the land to the east is warm, the sea tot he west is cooler

COLD OCCLUSION

12

Question 20

Polar Front Depression Pt 2

Refer to the diagram. What is represented by this on a weather chart

Answer 20

QUASI-STATIONARY FRONT

• An example of this happening is at the Polar Front where the Polar High air is coming from a NE direction and the Sub Tropical High air is coming from a SW direction
• The cold and warm air have an airflow direction opposing each other
• With no disruption, they will sit side by side - EXAMPLE

13

Question 21

Polar Front Depression Pt 2

A stationary front is assumed if the front is moving less than ____kts

Answer 21

5 KTS

13

Question 22

Polar Front Depression Pt 2

In a stable stationary front;

1. If the warm air being lifted is stable and the slope of the front is shallow, the cloud type formed is typically STRATIFORM or STRATIFORM WITH EMBEDDED SHOWERS AND;
2. The precipiation most associated with this will be SHOWERS or DRIZZLE
3. At very high levels, what type of clouds are present
4. If the warm air being lifted is stabel and the slope of the front is steep, the cloud type formed is typically STRATIFORM or STRATIFORM WITH EMBEDDED SHOWERS AND;
5. The precipitation most associated with this will be SHOWERS or DRIZZLE

Answer 22

1. STRATIFORM
2. DRIZZLE
3. ICE CLOUDS
4. STRATIFORM WITH EMBEDDED SHOWERS
5. SHOWERS

STATIONARY FRONT

14

Question 23

Polar Front Depression Pt 2

In an unstable stationary front;

1. If the warm air being lifted is conditionally unstable and the slope of the front is shallow, the cloud type formed is typically CUMULIFORM or STRATIFORM with embedded towering cumulus.
2. Thunderstorms will result if the air is WARM, MOIST, UNSTABLE or WARM, DRY, UNSTABLE
3. A shallow slope of an unstable stationary front will result in what 3 weather related circumstances in a broad and extensive range
4. Depending upon the slope gradient of the front and temperatures of the air masses, precipitation bands can vary from ____miles to ____miles

Answer 23

1. CUMLIFORM & STRATIFORM
2. WARM, MOIST, UNSTABLE
3. SHOWERS, FOG, POOR VISIBILITY
4. 50 to 200 MILES

• if the slope is steep or the front moves slowly towards the warm air mass, violent weather can result
• Heavy rain, severe thunderstorms, strong winds, and tornadoes are often associated with this type of front

STATIONARY FRONT

14