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Passage of a Depression – interactive animation
Depressions from our Weather and Climate teacher’s guide
Cold and Warm fronts activities for differentiation and revision
Finding weather features on a synoptic chart
Mid latitude weather systems basics: Teachers Notes, Introduction to the formation of a depression and Student Worksheet, more detailed PowerPoint about the formation of a depression, Student Worksheet – passage of a depression and
practise drawing a cross section through a depression PowerPoint exercise.
Identify the features of a depression on a simple weather map.
Cold and warm fronts – some activities for differentiation and revision.
Using WOW data to investigate a depression passing across the UK with worksheets for students including isoline drawing practice.
What is the weather? Work out what the weather is like at several UK locations based on some simplified weather maps.
Isotherm and Isobar drawing exercise based on a depression: student worksheet. A simpler version of the T/ isotherm map can be found here or a complete depression based exercise where students draw contours of temperature, pressure and precipitation to work out what the system looks like: Student worksheet and notes for teachers.
Weather and Climate: a Teachers’ Guide
Pathway: Extending Weather
Lesson overview: In this lesson we look at the causes of Low pressure systems and the weather they bring to the UK.
Depressions or low pressure weather systems, bring most of the ‘normal’ and ‘extreme’ weather that we experience in the UK. Driven by rising air, they mix colder and warmer air masses, forming fronts where these meet and bringing a predictable progression of weather as they pass over the UK. Their approach is typically first signalled by high cirrus cloud, which eventually develops into rain-bearing stratus. Once this passes there may be higher temperatures and less precipitation for a while, before towering cumulonimbus clouds arrive bringing heavy rainfall followed by lower temperatures and scattered showers.
To understand what low pressure is.
To know what weather a depression system brings to the UK.
To be able to draw and explain weather fronts.
To understand how weather changes in the UK as a depression passes over
Key Teaching Resources
Teacher CPD/ Extended Reading
Alternative or Extension Resources
Weather and Climate: a Teachers’ Guide
Passage of a depression
Use the following help sheet to write a fictional story about the passing of a depression. Imagine you are in the field taking observations and measurements. You should use all the statements included below.
|Coming of the warm front||At the warm front||Within the warm sector||At the cold front||Within the cold sector|
|Barometer – shows pressure is falling||Barometer – continues to show the pressure is falling.||No significant changes on the barometer.||Suddenly the pressure on the barometer begins to rise.||Pressure continues to rise.|
|Thermometer – shows the temperature is steady||Thermometer – shows the temperature is rising. Feeling a little sticky in this heavy coat!||Still quite mild.||Time for a hat, and to button up that coat, the temperature is falling, it’s becoming chilly.||It remains cold.|
|Cirrus clouds high in the sky, they begin to descend and thicken becoming altostratus.||Becomes darker, the clouds are low and cover the sky like blankets – nimbostratus.||Starting to see breaks in the cloud, a little drizzle now – nothing heavy.||Angry looking clouds, towering and grey, begin to form – cumulonimbus.||The clouds have thinned out now – some cumulus.|
|No need for the umbrella yet!||Time to get out the umbrella, continuous heavy rain.||A steady breeze, nothing too uncomfortable.||Heavy rain! Is that thunder I hear?||A few showers.|
|Slight increase in wind speed.||The wind is much stronger now – struggling to hold onto my umbrella.||Struggling to stay on my feet, as I’m battered by the strong winds.||Time to go home I think!|
Drawing Temperature and Pressure Contours
Lines of equal temperature – temperature contours, are called isotherms.
In this exercise, the task is to draw the 8.5°C, 6.5°C and 2.5°C isotherms. The 10.5°C and 4.5°C isotherms have already been drawn to help.
Start with the 8.5°C isotherm. This is the line which has everything warmer than 8.5°C on one side of it, and everything colder than 8.5°C on the other side. You could use a coloured pencil to colour in the dots for everywhere that is warmer than 8.5°C. Your isotherm is then the line which separates your coloured dots from the uncoloured ones.
Next, try the 2.5°C isotherm. For this, you could use a different colour to shade the dots for everywhere that is colder than 2.5°C.
Lastly, draw the 6.5°C isotherm. This will be very close to the 4.5°C isotherm in places, so be careful! To help with this, you could use a 3rd colour to shade the places where the temperature is 7 or 8°C, and a 4th colour to shade the places where the temperature is 5 or 6°C. Your line will divide the two.
Remember, contours can never touch or cross each other (it can’t be 8.5°C and 6.5°C at the same place!). The line should start and finish at an edge of the page.
Lines of equal pressure – pressure contours, are called isobars.
In this exercise, the task is to draw the 1016, 1012, 1008 and 1004mb isobars. However, to save space on the map, the pressure values have been recorded in shorthand – so 9 or 09 is short for 1009, 11 is short for 1011 etc.
On this map, we have some extra clues – these weather observations indicate the wind speed by the tail on the symbol. The wind is blowing from the tail of the arrow to the centre (the bars on the tail of the arrow tell you the wind speed) so –o is a wind blowing from the west to the east, or o—is a wind blowing from the east to the west. The wind tends to blow along the pressure contours, so your contours need to be roughly parallel to the tails on the closest weather symbols.
Start with the 1016mb contour. Where on the map are there places where the pressure is higher than that? If it helps, colour in those symbols where the value is greater than 16. Your pressure contour needs to divide those symbols from the others.
Now use a different colour to shade the symbols where the pressure value is 13, 14 or 15. Can you now draw the 1012mb isobar?
Again, use a different colour to shade the symbols where the pressure value is 9, 10 or 11. Can you now draw the 1008mbar contour?
Lastly, is there anywhere where the pressure is under 1004mb? If so, draw the 1004mb contour to separate off that observation from the others.
These two maps both correspond to the same weather situation. Can you work out what is going on?
– Where is the pressure lowest?
– How is the wind direction changing across the map?
– In general, where is the temperature lower and where is it higher?
– Where is the temperature changing most rapidly? Remember that a front is where cold and warm air meets. You can use the wind information on the second map to see where the cold air is pushing into the warm air (a cold front) or whether the warm air is pushing into cold air (a warm front).
Isobars are lines of constant pressure. Drawing the isobars reveals features (eg highs, lows, ridges and troughs) which help us understand the weather.
When trying to draw isobars, remember the following
– You are trying to draw the isobars of pressure for the values below the
– The symbols on the map give the observed pressure and wind speed and
direction. Remember that the wind is blowing from the tail of the arrow
to the centre. The bars on the tail of the arrow tell you the wind speed:
– The wind blows almost parallel to the isobars (they are usually blow
slightly more towards the centre of the low pressure area). If you stand
with your back to the wind in the northern hemisphere the pressure is
lower on your left than on your right.
– Isobars tend to be parallel to each other, don’t wiggle and never cross.
– The closer the isobars are to each other, the stronger the wind. You can
use the bars on the tail of the weather station symbol to give you the
Beaufort force of the wind. Look at the scale at the top of the map (this is
called the ‘geostrophic scale’). The distance from the left hand edge of
the scale to the force at the symbol gives you the spacing between 2mbar
isobars at that point.
A Case Study of a Weather System using WOW data
Go to the WOW website wow.metoffice.gov.uk
Use the pop up calendar to select 24th December 2015 and the drop down box to choose 0600 to 0659 in the morning.
Use the Layers menu on the right to select wind speed/ direction.
Where is the wind coming from?
Is the wind weak or strong?
Change the time to 0800-0859. How does the wind look now?
Change the time to 1200-1259. How does the wind look now?
Capture the image, stick it into a work book
NOW USE THE LAYERS MENU TO LOOK AT TEMPERATURE.
At 0600-0659, what are the temperatures across the U.K.? (You may need to click on some dots to work out exactly what the temperature is)
Capture the image, stick it into a work book at draw a line roughly dividing colder and warmer temperatures. What is a line dividing cold and warm temperatures called?
Now look at the temperature between 0800-0859. What is the pattern of temperatures?
Now look at the temperature between 1200-1259. What is the pattern of temperatures?
Capture the image, stick it into a work book at draw a line dividing colder and warmer temperatures.
Now compare this image and the line you have drawn on it with the wind image you captured earlier. What do you notice?
Find the Met Office Weather Station in Glasgow/ Bishopton, and click on it. Click on ‘View Full Observation’ and use the Graph view and the calendars to select from
23/12/15 to 25/12/15. How does the air temperature change?
NOW USE THE LAYERS MENU TO SELECT RAINFALL RATE AT 0600-0659
You’ll also need to add ‘WOW observations’ from the Filter menu because the official observations don’t include rainfall. Where is it raining?
Go back in time, hour by hour, what happens to where the rain is?
NOW USE THE LAYERS MENU TO SELECT ‘PRESSURE’.
Investigate how that changes through the day.
Find the Met Office Weather Station in Glasgow/ Bishopton again, and click on it. Click on ‘View Full Observation’ and use the Graph view and the calendars to select from 23/12/15 to 25/12/15. How does the mean sea level pressure change?
Capture the pressure image from 1200-1259 on 24th December 2015.
Can you sketch pressure contours for 992, 996, 1000, 1004, 1008 and 1012hPa?
Summarise what you think is going on with the weather on the 24th December 2015.