Mid-Latitude Depressions Flashcards

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1
Q

What is a mid-latitude depression?

A

Low pressure weather system caused by meeting of polar and tropical maritime air masses at polar front

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2
Q

The passing of a depression follows a 3 stage model:

A

1) Embryo
2) Maturity
3) Decay

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3
Q

Outline embryo stage of depression

A
  • TM air meets cooler, denser PM air
  • Convergence results in spiral movement as PM air forces TM air upwards, twisting a result of Earth’s movement
  • Rising air decreases pressure behind warm front, rising air removed by strong upper atmosphere winds
  • Moves in NE direction due to southwesterlies and Coriolis effect
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4
Q

Outline mature stage of depression

A
  • Pressure continues to decrease as air rises at warm front over cold air
  • Rising air reaches ‘dew point’ increasing temps, due to saturation and formation of clouds = Precipitation
  • Precipitation decreases within warm sector due to increase in temp and decrease in uplift
  • Cold front, steep gradient formed by rapid undercutting
  • Warm TM air rises due to undercutting of PM air, cumulonimbus clouds develop = Heavy rainfall
  • Cold front approaches, wind speeds increase due to increasing pressure gradient
  • Wind speeds increase as cold front passes, then decreases in cold sector
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5
Q

Outline decay stage of depression

A
  • Cold front moves faster than warm front
  • Cold front catches up with warm front, lifting warm air from ground (Occluded front)
  • No TM air at surface
  • Depression infills with cold air, precipitation decreases, pressure increases and wind speeds drop
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6
Q

What weather is associated with a warm front?

A
  • Precipitation: Continuos drizzle
  • Cloud: Nimbostratus
  • Wind direction: SW
  • Wind speed: Increase
  • Temp: Remains stable
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7
Q

What weather is associated with a warm sector?

A
  • Precipitation: Isolated shower at most
  • Cloud: Stratus
  • Wind direction: Changing from NW to SW
  • Wind speed: Low
  • Temp: 4-6°C increase
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8
Q

What weather is associated with a cold front?

A
  • Precipitation: Heavy rainfall
  • Cloud: Cumulonimbus
  • Wind direction: NW
  • Wind speed: Increase
  • Temp: Remains stable
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