Fronts

Question 1

What is a front

Answer 1

Two air masses of different temperature and humidity meet

Question 2

+++ signed along the front means

Answer 2

Weakening

Question 3

. . . Along front means

Answer 3

Increasing or developing

Question 4

Frontogenesis means

Answer 4

Formation of front

Question 5

Frontocysis means

Answer 5

Decay of a front

Question 6

Quasi Stationary Front

Answer 6

Not much movement (5kts)

Little interaction so no sig weather

Wind flows from cold to warm and is deflected 90 degrees to blows along frontal zone

Question 7

Cold front

Answer 7

Cold air replace warm air at surface

Unstable CB/TCU/CU

Precipitation zone 150km/300km wide

Slope 1:80

Question 8

Cold front slope

Answer 8

1:80

Question 9

How far does cloud extend in cold front

Answer 9

50-100nm

Question 10

Clouds when approaching cold front

Answer 10

CB/TCU/CU

Question 11

Temperature and pressure at cold front

Answer 11

Temp decreases
Pressure is lowest at the front
Pressure increases after front

Question 12

Warm front is

Answer 12

Warm air replacing cold at at surface
Stable CI/CS/AS/NS
1:150 slope
Continuous and moderate rain

Question 13

What happens to pressure/temp at warm front

Answer 13

Temp increase
Pressure decreases
Humidity increases

Question 14

How fast does a warm front move

Answer 14

10-15kts

Question 15

How fast does a cold front move

Answer 15

20-20kts

Question 16

Pressure at warm/cold front

Answer 16

Isobars bend at fronts
Warm front pressure decreases
Cold front passes pressure increases

Question 17

Mediterranean front

Answer 17

Only occurs in winter
Cold air moving down from continental Europe
Warm air moving up through North Africa

Polar air meets tropical air

Question 18

The Artic Front

Answer 18

Only occurs in winter

Division between maritime artic and maritime polar

Question 19

Polar fronts

Answer 19

Meeting of polar air and sub tropical air

Summer warm air mass in line past UK and NE Canada

In winter cold air moves south across Atlantic (Florida to uk)

Question 20

Polar front depression formation

Answer 20

Occurs at a stationery front
Warm air backs into cold air and cold air back into cold
Causes warm air to rise causing a pressure gradient
More air drawn into cold air to strength the low level winds
Deflection via Coriolis anticlockwise to form a low pressure system

Question 21

Polar front stages

Answer 21

Stationary front
Frontal wave
Open wave
Mature (initial occlusion)
Advanced inclusion
Cut off cyclone

Question 22

Warm front - clouds/precipitation/slope/temp/pressure/humidity

Answer 22

Warm air slide over colder air
Frontal slope is shallow around 1:150
Rises slowly and cools adiabatically
Stratiform clouds

Cirrus clouds - cloud base lowers altostratus/nimbostratus/stratus - clouds can extend 500 miles ahead

Freezing rain/drizzle - precipitation zone 350km ahead

Temp goes up
Pressure decreases
Humidity goes up

Moves at 10-15kts

Question 23

Where are the strongest winds in a polar front depression

Answer 23

Occurs between polar air tropopause about 300-400nm ahead of warm front

Question 24

Warm front speed

Answer 24

Speed of about 10-15kt 2/3rd of Geostrophic wind speed

Question 25

Warm front winds

Answer 25

Backs initially then veers at the front with steady increase in speed South Westerly to Westerly at the warm sector

Question 26

Warm sector - source/clouds/precipitation/temp/pressure/humidity

Answer 26

Temperature increases Pressure decreases Relative humidity decreases Winter can bring stratus Summer - clear skies and fair weather cumulus/haze sometimes Stable tropical maritime air Light precipitation

Question 27

Cold front - precipitation/clouds/slope/temp/pressure

Answer 27

Cold dense air slides underneath warmer tropical maritime air Cools adiabatically/ELR increases rapidly/instability Intense line of CB clouds the entire length of cold front Thunderstorms just head of surface position of front Heavily embedded cbs in NS/AS Intense precipitation/heavy snowfall in winter Slope is 1:80 Weather band is 30-50nm wide Temp decreases Pressure lowest at front then increases Humidity increases

Question 28

Passage of wind along polar front depression

Answer 28

Moves from south westerly before warm front Moves westerly at warm sector Moves north westerly at cold sector

Question 29

Warm Occlusion

Answer 29

Cold air catches up to displace warm sector but coldest air at the front - Common in the winter Cross Section would show cold air at back rising above more dense colder air at front with warm sector in the middle off the ground. Embedded CBS ahead of occlusion Cirrus/AS/Snow/rain/stratus at warm front Towards back embedded CB/NS/AS

Question 30

Cold Occlusion

Answer 30

Coldest air at the back of front - common in summer Cross section: Colder more dense air at rear of front would cause rear polar maritime air to undercut the warmer air at front. Warm sector will be hovering off the ground above. Precipitation falls on both side Embedded CBS

Question 31

Approximate latitudes of polar front in NH in summer and winter

Answer 31

Summer 60N Winter - 50N

Question 32

Precipitation zone ahead of warn front

Answer 32

200nm

Question 33

During the passage of a cold front what wind conditions can you expect

Answer 33

Westerly winds becoming north westerly and increasing

Question 34

Polar Low

Answer 34

Small intense maritime cyclone that form in cold polar air that moves over warmer water 100-500km and last between 12/36 hours

Question 35

What has the highest likelihood of encountering thunderstorms/CBS and convective clouds.

Answer 35

Slow moving cold front

Question 36

Most mid latitude depressions move from west to east in both hemispheres

Question 37

Where is the worst weather in an occluded front

Answer 37

Near the apex of the occlusion

Question 38

Weather development on approach to a warm front

Answer 38

800km ahead of surface overcast cirrostratus Cloud base lowers to become overcast altostratus Nimbostratus next Around 300km ahead of surface the ac encounters rain which intensifies

Question 39

Typical lifespan of a mid latitude depression

Answer 39

4 to 7 days

Question 40

Cold front speed

Answer 40

20-25 knots

Question 41

How long does a cold air pool last

Answer 41

Typical 3 days