Fronts and frontal depressions

Question 1

What separates two air masses of different temperature / density

Answer 1

Weather front

Question 2

How wide can a front be?

Answer 2

Up to a few kilometres wide. Often described as a zone where the change is gradual.

Question 3

There are 3 main global frontal systems

Answer 3

Polar front
Artic front
Equatorial Trough / ITCZ
(also Mediterranean front in Europe)

Question 4

Warm front:
Describes which part of the front

Answer 4

Leading edge

Question 5

Warm front:
How does it move in relation to the retreating cold front?

Answer 5

Rises over and replaces

Question 6

Warm front:
Have a greater effect on the weather in (spring/summer/autumn/winter)?

Answer 6

Winter

Question 7

Warm front:
What is the expected angle of the front. It slopes upwards at a gradient of

Answer 7

1:150

Question 8

Warm front:
Conditions as surface front approaches:
Clouds?

Answer 8

High clouds, progressively lowering as the surface front nears.
Ci - Cirrus
Cs - Cirrostratus
As - Altostratus
Ns / St - Nimbostratus / Stratus

Question 9

Warm front:
Conditions as surface front approaches:
Weather?

Answer 9

Steadily worsening to intermittent/continuous rain/drizzle/snow at the front.

Question 10

Warm front:
Conditions as surface front approaches:
Pressure?

Answer 10

Steadily falls as the warm front approaches

Question 11

Warm front:
Conditions as surface front approaches:
Wind?

Answer 11

Backs - the veers as the front passes

Question 12

Warm front:
Conditions as surface front approaches:
Aviation hazards

Answer 12

Potential FZRA/FZDZ
moderate rime icing
low cloud
poor visibility
possible mist / fog

Question 13

Cold front:
Have a greater effect on the weather in (spring/summer/autumn/winter)?

Answer 13

Winter

Question 14

Cold front:
Slope forwards/backwards and at what gradient?
Any exceptions

Answer 14

Generally backwards
1:75
Small forward sloping section at the surface

Question 15

Cold front:
Conditions at a cold front:
Cloud - Initially, then and after?

Answer 15

Nimbostratus [Ns] and Stratus [St] with embedded Cumulus [Cu] / Cumulonimbus [Cb]
Then
(mid level 6500ft +)
Altostratus [As] Altocumulus [Ac]
(High level 20,000ft+)
Cirrostratus [Cs] Cirrocumulus [Cc]

Then well behind the front:
Cirrus [Ci]

Question 16

Cold front:
Conditions at a cold front:
Weather?

Answer 16

Heavy intermittent or continuous rain with showers at or just ahead, decreasing further behind the front.

Question 17

Cold front:
Conditions at a cold front:
Ground visibility?

Answer 17

Poor during precipitation, improving further behind

Question 18

Cold front:
Conditions at a cold front:
Pressure?

Answer 18

Slight decrease on approach, increases after the passage of the front

Question 19

Cold front:
Conditions at a cold front:
Aviation hazards:

Answer 19

CBs
heavy showers of Rain [RA]

Possible:
Hail [GR] or small hail [GR]
Clear icing
Wind gusts/wing shear
Lightening

Question 20

Warm sector:
What type of air mass is typical?
Where does this live in relation to fronts?

Answer 20

Tropical maritime
Between warm and cold fronts

Question 21

Warm sector:
Properties - Cloud?

Answer 21

Stratus (St)
Stratocumulus (Sc)
Fog / mist

Question 22

Warm sector:
Properties - Weather?

Answer 22

Light drizzle

Question 23

Warm sector:
Properties - Ground visibility?

Answer 23

Moderate, poor in low cloud, drizzle mist and fog or good in the summer with fair weather Cumulus (Cu)

Question 24

Warm sector:
Properties - Pressure and wind?

Answer 24

Constant
Wind constant, from West or South-West

Question 25

Warm sector:
Properties - seasonal effects?

Answer 25

Winter fronts usually produce more weather and lower clouds

Question 26

Occluded front:
Formed by?

Answer 26

Cyclogenesis, when a cold front catches up and then
Overtakes a warm front.

Question 27

Occluded front:
What word is synonymous with ‘occluded’ and how does this relate?

Answer 27

The air in the warm sector is separated (occluded) from the surface.

Question 28

Occluded front:
Shares characteristics from…

Answer 28

The weather has the characteristics of both warm and cold fronts.

Question 29

Occluded front:
The sequence of clouds ahead of the occlusion is similar to the sequence of
clouds ahead of a____ _____

Answer 29

warm front.

Question 30

Occluded front:
The cold front weather occurs near the _____ _____ _____

Answer 30

upper cold front.

Question 31

Occluded front:
The worst weather is near the ____ __ ___ _________

Answer 31

apex (tip) of the occlusion.

Question 32

In Europe warm Occlusions are more common in ______ ….

Answer 32

winter; cold occlusions in summer.

Question 33

How can the precipitation area be described near a quasi-stationary front?

Answer 33

A wide area on the cold-air side and sometimes patchy along the line of the front itself.

Question 34

Most mid-latitude depressions move from ____ to ____ in both hemispheres, powered and pushed by the prevailing westerlies and jet-streams.

Answer 34

Most mid-latitude depressions move from west to east in both hemispheres, powered and pushed by the prevailing westerlies and jet-streams.

Question 35

The whole polar front moves In the direction, and parallel to the isobars in the warm sector at a speed determined by the

Answer 35

geostrophic interval of the warm sector isobars.

Question 36

An individual front moves approximately _____________ to the front or more or less __ ____ with the isobars behind the front.

Answer 36

An individual front moves approximately perpendicular to the front or more or less in
Line with the isobars behind the front.

Question 37

The speed of the front is calculated by using?

Answer 37

The geostrophic interval along the front itself.

Question 38

Do warm or cold fronts move faster?

Answer 38

Generally cold fronts move faster than warm fronts.

Question 39

Cold fronts move approximately equal to the ___________ _______

Answer 39

Cold fronts move approximately equal to the geostrophic interval.

Question 40

Warm fronts move at approximately 70% of ___ ____________ ________

Answer 40

Warm fronts move at approximately 70% of the geostrophic interval.

Question 41

A polar front depression moves in the direction, and parallel to,

Answer 41

the isobars in the warm Sector at a speed determined by the geostrophic interval of the warm sector isobars.

Question 42

The stages and life cycle of a mid-latitude depression are

Answer 42

Cyclogenesis
Mature,
Occluded
Frontolysis,

Question 43

Westerly waves; The west to east passage of waves of weather associated with

Answer 43

polar Front depressions or mid-latitude lows,

Question 44

Mountains can strengthen or weaken fronts, accelerate or decelerate fronts and
make fronts harder or easier to analyse and predict.
What can this depend on?

Answer 44

• Depends on the orientation of the front and mountain axis.
• Channelling, blocking and other terrain induced flows modify the front.

Question 45

On surface weather charts, use the ______ to assess the direction relative to ____ _____. Make corrections for land and sea tracks, and calculate the wind speed using the ______ _______ and the ____________ wind scale.

Answer 45

On surface weather charts, use the isobars to assess the direction relative to true
north. Make corrections for land and sea tracks, and calculate the wind speed using
the isobar spacing and the geostrophic wind scale.

Question 46

Atmospheric divergence / convergence

Answer 46

Sinking (high pressure) tends to be more gentle so pressure gradients are less; isobars are further
apart and wind is slower.

Rising (low pressure) The ascent can be strong so pressure gradients can be greater, isobars closer and wind will be faster.