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Last week we Last week we saw why saw why
sometimes we sometimes we get clear skies get clear skies
and warm sunny and warm sunny weatherweather
But we haven’t had much But we haven’t had much at that this year!at that this year!
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Why?Why?
We have had a lot of low We have had a lot of low pressure areas called pressure areas called
DepressionsDepressions
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At this point …At this point …
I hope we can watch a BBC video which explains it a rather wellhttp://www.bbc.co.uk/learningzone/clips/clips/s_geog/bb/s_geog_ec_02985_4x3_bb.asx
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Warm air and cool air do not mixBetween 45N and 64N cold air from the poles meets warm air from the topics to form a polar front
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As warm air meets cold air, the temperature gradient is strengthenedThis leads to instability and a wave forms that develops into a triangular shape – warm air inside the triangle and cold air outside it
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The leading edge of the depression is called the warm front. Here the warm air, which is lighter rises above the cold air in front of it.The cold air moving behind the warm air travels faster and pushes its way under the warm air. This is a cold front
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At the top of the triangle pressure falls as the warm air rises in a spiral movement.Winds develop and blow around the centre of the low pressure in an anticlockwise direction.The boundary between the warm air and the cold air is called a front
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Behind the cold front
At the cold front
In the warm sector
At the warm front
Ahead of the warm front
It remains cold
Clouds thin The wind is
still a bit blustery
There are showers.
There’s a sudden drop in temperature
Clouds thicken into big cumulonimbus clouds
Wind speeds increase, sometimes to gale force
There’s heavy rain, sometimes with hail, sleet and thunder.
The temperatures are mild
The cloud becomes thinner and breaks
The wind steadies
The rain turns to drizzle and stops
Temperatures continue to rise
The clouds get thicker and lower (known as nimbostratus)
The rain is continuous and sometimes heavy
the wind veers and becomes blustery
There is high thin cloud called cirrus
No rain at first It is quite cold
but the temperatures start to rise
wind speeds increase
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What are the expected weather conditions at each stage of a depression as it crosses Britain?
What are the expected weather conditions at each stage of a depression as it crosses Britain?
Reading to learn!
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Marge decides to give up on a day outdoors as the
rain hasn't stopped for hours! She decides to go
shopping instead.
Strong winds nearly blow Bart
off his skateboard!
Lisa checks out her ‘Guide to Clouds’
book to find out the name of clouds that are high in the sky!
“Grampa” switches on the news to
hear that a weather depression going to affect Britain
soon
Maggie cheers up
when the sun comes out!
Bart finds a new jacket in the park that’s just his size! “Excellent”,
he says, “its started to get cold and it looks
like it might rain!”
Chief Wiggum ventures out of his police car after heavy rain and thunder to buy his coffee and doughnut. He wasn’t
expecting to get caught in a rain shower!
Where in the depression...? Read the following statements from characters in ‘The Simpsons’. Decide which section of the depression (1-5) they are most
likely to be referring to. Write your chosen number it in the box next to each statement. Be ready to justify your decisions!
Categorising information and making decisions to
learn!
Challenge!There are two blank speech bubbles.
Create two appropriate statements for a stage of the depression