Be able to describe and explain the type of weather associated with the different fronts in a depression Be able to describe how the weather changes with the passage of a depression Be able to reproduce a diagram of a crosssection of a depression ID: 930943
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Slide1
Depressions- associated weather
Slide2Be able to describe and explain the type of weather associated with the different fronts in a depression.
Be able to describe how the weather changes with the passage of a depression.
Be able to reproduce a diagram of a cross-section of a depression.
Objectives
Slide3Cool air ahead of warm front
Warm Sector
The different types of air…
Warm front
Cold Front
Air rotates around the centre of the depression
Q
Warm Tropical air
Cool Polar Air
Around the depression, air coming from different areas are drawn together. They do not mix. Boundaries between these different air types are what we call ‘fronts’.
Slide4Direction of movement
A
B
A
Cool
Polar Air
Warm
Tropical Air
(
Warm
Sector)
Cool
Air
Cross-section through depression Klaus…
Slide5Cross-section through the depression…
Direction of movement
Showers
Rain (3-4 hours)
Heavy rain (1-2 hours)
Slide6As the warm air
meets the
cool air it is forced to rise, as it is less dense.As it rises the air cools allowing moisture to condense. Clouds form.
Clouds are found along the boundary between the warm air and cool air. This is the warm front.
Where the front is high in the sky, temperatures are low and the clouds are made of ice, These are Cirrus clouds.
The passage of a
warm
front
Slide7As the warm front approaches the ground, the cloud is at its thickest and rain starts to fall. This rain usually lasts around 3-4 hrs and can be heavy at times.
As the front gets closer it is lower in the sky, the clouds become thicker. This is Nimbostratus cloud
When the warm front has passed the cloud becomes much thinner and the rain stops. A little drizzle can fall.
The passage of a
warm
front
Slide8The passage of a cold front
As the dense cold air pushes forward, it pushes under the lighter warm ahead
ahead and forces it to rise.As it rises moisture within the air cools, condenses and thick Cumulonimbus cloud forms.
Rain can be heavier but is only likely to last 1-2 hrs. Occasionally thunder and lighting and sometimes even tornadoes may occur as the front passes
Once the front has passed, skies clear and there is some sunshine but, after an hour or two, showers develop in the polar maritime air.
Slide9Weather associated with the passage of a depression
Ahead of the warm front
At the warm frontIn the warm sector
At the cold front
In the cold air
Surface PressureStarts to fallContinues to fallSteadyStarts to riseRise continuesTemperatureCoolRisingFeeling milder Sudden dropFeels cold Cloud CoverThin cirrus at first but cloud thickens and lowersThick cloud with a low base. (Nimbostratus)
Thin cloud which may break at timesCloud rapidly thickens (Cumulonimbus cloud)
Occasional small cumulus cloud.Winds
Speed increase and direction slowly turns.Speed increases and becomes gusty. Direction turnsSpeed and direction remain steadySpeed increases rapidly with strong or even gale force gusts.Direction changes sharply
Speed decreases but with strong gusts especially around showersRainfallNone at first but rain starts and becomes heavier as cloud thickensContinuous rain often heavy.Heavy rain stops and is replaced by patchy drizzleHeavy rain with the possibility of hail and/ or thunder.Showers