Front Basics, PFDs, Warm Fronts, Warm Sector

Question 1

What does it mean if a front is drawn “hollowed out”

Answer 1

It indicates the aloft position of the front

Question 2

Describe what a cold front looks like on a surface pressure chart

Answer 2

Blue, triangles pointing in direction of travel

Question 3

Describe what a warm front looks like on a surface pressure chart

Answer 3

Red, semicircles pointing in direction of travel

Question 4

Describe what an occluded front looks like on a surface pressure chart

Answer 4

Purple, triangles and semicircles pointing in direction of travel

Question 5

Describe what a quasi-stationary front looks like on a surface pressure chart

Answer 5

Blue triangles and red semicircles pointing in opposite directions

Question 6

A warm front is when…

Answer 6

Warm air displaces cold air

Question 7

A cold front is when…

Answer 7

Cold air displaces warm air

Question 8

Which temperature of air always undercuts the other, why, and what does this create

Answer 8

Cold, as it is denser. Creates a local “frontal inversion”

Question 9

Describe in a few of steps how a polar frontal depression is formed

Answer 9

1. Quasi-stationary front at polar front
2. Due to jet stream, small wave like disturbances occur along the front, forming small low pressure areas
3. Wedge of warm tropical air pushes into the cold air at the surface
4. low pressure area draws air from both sides, which converges and rises, creating even lower pressure
5. Wind curves towards and around the tip of the wedge
6. Full fronts form

Question 10

How does cloud in a warm front form, and what type of cloud is it

Answer 10

Warm air rises over cold, cools adiabatically, and condenses into stratiform cloud

Question 11

What are the signs of an incoming warm front, and how far in advance can they be seen

Answer 11

High cirrus cloud anywhere from 600-800km ahead
Cloud gradually lowering and thickening into altostratus
Cloud continues to get lower, with increasing precipitation and decreasing visibility

Question 12

What precipitation can be expected with a warm front, and how far in advance can this be expected

Answer 12

Clouds become thick enough to bear rain 200nm from front.

Rain can be expected, along with FZRA and FZDZ if passing over a cold landmass eg in winter

Question 13

What happens to temperature and dew point in a warm front

Answer 13

Steadily increases

Question 14

What happens to visibility in a warm front

Answer 14

Steadily decreases, with fog at the front

Question 15

What happens to surface pressure in a warm front

Answer 15

Falls, then steadies in the warm sector

Question 16

What happens to cloud and precipitation in a warm front

Answer 16

Base lowers, and precipitation steadily increases

Question 17

What happens to the wind in a warm front

Answer 17

Backs, then veers at the front. Speed steadily increases

Question 18

What conditions can be expected in the warm sector in winter and summer respectively

Answer 18

Winter: widespread low stratus or stratocumulus, potentially clear skies if low humidity
Summer: fair weather cumulus over land. If tropical continental air, clear skies due to dryness of the air

Question 19

What happens to surface pressure in the warm sector

Answer 19

Falls slightly, until cold front arrives

Question 20

What happens to the wind in the warm sector

Answer 20

Remains constant from west or southwest, along the isobars