Mid-latitude cyclones

Question 1

Other names for mid-latitude cyclones

Answer 1

frontal depression, extratropical cyclone, temperate cyclone

Question 2

Origin:

Answer 2

forms at 60 degree N & S latitude at polar front, where warm air from subtropics meets cold air from poles.

Question 3

Circulation:

Answer 3

in S hemisphere, air moves clockwise into centre of LP pressure system - converges and rises.

Question 4

Diameter

Answer 4

1000-4000 km wide

Question 5

Movement

Answer 5

in Rossby waves (help transfer heat from the tropics toward the poles and cold air toward the tropics in an attempt to return atmosphere to balance) from West to East within westerly wind belt (30 -60 latitude); travel at speeds of 40 - 90 km/h.

Question 6

Season

Answer 6

all year round, but mostly influence our weather in winter when CF bring rain to SW cape. In Summer, they migrate south with shifting of sun’s rays and little effect on SA weather.

Question 7

Duration

Answer 7

2-5 days, but can last up to 14 days

Question 8

Where is the worst weather experienced within the cyclone?

Answer 8

closest to centre of LP

Question 9

Stages in formation of mid-latitude cyclone (cyclogenesis):

1st stage

Answer 9

Initial/developing/wave stage:
forms at polar front; warm, moist sub-tropical air meets cold, dry polar air.

2 air masses move in opposite directions (don’t mix)

the disturbance, due to rotary movement, causes LP to form at wavepoint.

Question 10

Stages in formation of mid-latitude cyclone (cyclogenesis):

last stage

Answer 10

Mature (warm sector) stage:
cold & warm fronts develop. Air circulates clockwise around and into the low pressure and rises.

warm front: warm air rises gradually over cold air ahead of it.

cold front: cold air wedges in under warm air, forcing it to rise sharply.