Lesson video

My name's Miss Hoggett, and I'm really excited you're here to learn some geography with me today.

I'm sure if you try your best, you're going to be absolutely fantastic.

Don't worry too much if you haven't studied this topic before.

I'm here to help you every step of the way.

Our title for today is weather and climate forecasting, and this sits within the unit, weather and climate, how do they vary? Our learning outcome for today is that I can describe and read a weather forecast.

To help us through today's lesson, there's a number of key words that are going to be really useful to us.

Front, prediction, isobars and air pressure.

Front.

A weather front is the boundary between a warm air mass and a cold air mass.

Prediction.

A statement about what could happen in the future, usually based on evidence.

Isobars.

Lines on weather maps that join areas with the same air pressure.

And air pressure, force exerted by the weight or mass of the column of air above a place.

So front, prediction, isobars and air pressure are going to be really useful in today's lesson.

So today's lesson is split into two learning cycles.

How are weather forecasts displayed and how are air pressure and weather fronts shown? We're going to start with our first learning cycle now.

How are weather forecasts displayed? So weather forecasts show us what the weather will be like over the next hours, days and weeks.

We know that in the UK we can experience lots of different types of weather all in one day.

So it's useful to look at weather forecasts to help us know what to expect.

Weather forecasts are a prediction of the weather that we expect.

A prediction is a statement about what could happen in the future.

And it's usually based on evidence.

We can find weather forecasts in lots of different places.

They can be seen on the TV, on apps or printed in newspaper.

If you've got a phone nearby, pause the video now and see if you can find a weather app on your phone.

Did you manage to find one? It might look similar to the image that you can see on the slides.

If you couldn't find one, watch the news later and you'll be able to see a weather forecast presented on the news.

If I was watching a weather forecast on the telly, I might expect it to sound something like this.

Good evening London.

Let's take a look at the weather forecast for today and the days ahead.

Expect a mix of sun and clouds throughout the afternoon with temperatures hovering around 12 degrees Celsius.

Winds will be light coming in from the southwest at about 15 kilometres per hour, making it feel a bit milder than it has been recently.

So whilst it might be a good idea to grab a jacket, it's certainly not a day to bundle up too much.

As we head into the evening, those clouds will begin to thicken and there's a chance of light rain arriving after 9PM.

Temperatures will drop to around 7 degrees Celsius, so it will feel a bit chillier overnight.

Looking ahead to the weekend, Saturday will start off cloudy with some light showers expected throughout the day and highs will remain around 10 degrees Celsius.

Sunday will see a slight improvement with more dry spells, although temperatures will be on the cooler side, with highs of 11 degrees Celsius.

So for the rest of the day, you might want to keep an umbrella handy just in case, and make sure to dress in layers if you're heading out this evening.

That's your London weather update.

Stay tuned for more news coming up after the break.

Scientists also create special maps called synoptic charts, or surface pressure charts, to show us the forecast.

On the screen you can see a surface pressure chart from the Met Office.

It contains lots of different features that we'll touch on in today's lesson.

Surface pressure charts are important because they show us pressure patterns at the Earth's surface.

Pressure is shown by isobars, which are the black lines that we can see, and we'll explain this further in a moment.

We also have the small numbers on there, which are representing the millibars of pressure in different places across the Earth's surface.

Let's check your understanding so far.

Which of the below options best describes a surface pressure chart? A, a map showing the distribution of temperature across different regions of the Earth's surface.

B, a map showing the pressure patterns at Earth's surface.

Or C, a map showing wind speed and direction at different altitudes in the atmosphere.

Pause the video and have a go at completing this practise task.

If you said B, a map showing the pressure patterns at Earth's surface.

Good work geographers, you're doing a brilliant job.

Now weather can also be represented using symbols.

These symbols make it easy to understand the weather quickly.

You've probably seen a number of these different symbols before.

Pause the video and have a go at working out what these symbols represent based on what you already know.

How many did you get? Let's see which ones we got right.

Some commonly used weather symbols include a sunny day represented by a small yellow sun.

Cloudy represented by a single white cloud.

If there's a light rain shower expected in the day, we might see a cloud with a little bit of rain and half a sun in the background.

A grey cloud that says hail underneath represents hail.

A white cloud with drizzle underneath represents drizzle.

A grey cloud with a snowflake and a raindrop underneath represents sleet.

But if it just has two snowflakes underneath, it's going to represent heavy snow.

This box that says fog represents fog.

If there's heavy rain, there'll be a dark grey cloud with two raindrops.

And if there's thunder and lightning expected, we would see a lightning bolt in front of a grey cloud.

So these are some of the commonly used weather symbols.

Now, weather forecasts are really useful as they help people know how to plan their day.

Aisha says, "I packed sunglasses as I thought it would be a sunny day today." But Luca says, "Well, I packed my umbrella because the weather forecast predicted rain." So Lucas used the weather forecast to help prepare him with what he needed to take for the day.

Sometimes this can impact people's jobs, particularly if they have jobs that work outside, so it can help people know how to prepare for their day.

We're now going to practise what we've learnt so far.

So in the boxes, I'd like you to write the correct type of weather being shown by each symbol.

Pause the video and have a go at completing this practise task.

Well done for giving that a really good go, geographers.

Let's check your answer.

So our first symbol, the yellow sun, represents a sunny day.

Our white cloud is cloudy.

Then we have a light rain shower during the day.

Then we have hail, drizzle.

We then have sleet, heavy snow, fog, heavy rain and thunder.

I'm sure you got all of those spot on.

Well done for being fantastic and working really hard.

We're now ready to move on to learning cycle number two, how our air pressure and weather fronts show.

So on the screen, we can see a typical synoptic chart.

It shows a range of different weather features.

We can see on the map that we have got weather fronts and we also have air pressure being represented.

Now, air pressure is the force exerted by the weight or mass of the column of air above us.

In the diagrams, we can see that we have high pressure areas and low pressure areas.

High pressure areas are where the air is pushing down on the earth and it's applying that high pressure to the surface.

Low pressure areas are where the air is moving away from the earth.

And therefore, it's not pushing that pressure down.

And we have low pressure areas.

Now, air pressure has an impact on the weather that we experience.

High pressure generally brings sunny and calm weather, but low pressure generally brings rainy and stormy weather.

So the type of pressure that we have is really important in predicting what type of weather we're likely to experience.

Synoptic charts show this air pressure and it shows how pressure varies across geographical space.

To do this, they use isobars, which join areas of equal pressure.

Izzy says, "They look a bit like contours on an OS map!" And she's spot on because contour lines join up areas of equal height above sea level.

And isobars do the same thing, but this time they're representing pressure.

Now, low pressure systems have tightly packed isobars that bring strong winds that spiral inwards in an anti-clockwise pattern.

We can see in the diagram that the green arrows are representing an area of low pressure, the isobars are really close together, and the arrows are moving in an anti-clockwise pattern.

Now, because the isobars are close together, we know the winds are strong because the pressure changes really quickly.

Strong winds blow in an anti-clockwise direction around the low pressure area.

On the other hand, high pressure systems have widely spaced isobars that bring light winds that blow outwards in a clockwise pattern.

So it's almost the opposite.

We can see the green arrows are moving in a clockwise direction.

And the isobars bars are really far apart so it's not gonna be that windy because the pressure doesn't change very quickly.

You can see these isobars on this synoptic chart here.

Here we have an area of low pressure, whereas here we have an area of high pressure.

It's really easy to identify these on a synoptic chart because usually an L will be used to represent an area of low pressure, and a H will be used to represent an area of high pressure.

So they're really easy to spot.

Let's check your understanding.

So, high pressure systems have tightly packed isobars.

True or false? Pause the video and have a go at completing this question.

Well done if you said false.

High pressure systems have widely spaced isobars that bring light winds and blow outwards in a clockwise pattern.

Now, synoptic charts also show weather fronts.

Weather fronts are the boundary between two air masses.

The UK is affected by cold and warm air masses.

So we can see that the UK is affected by our cold air masses, including our Arctic maritime, our polar continental, polar maritime and returning polar maritime.

And we also have our warm air masses, such as our tropical maritime and our tropical continental.

Now the reason they're called maritime and continental depends on whether they've travelled over land or sea.

If they've travelled over land, they're called continental, and if they've travelled over sea, then they're called maritime.

Now the UK is sometimes referred to as a bit of a roundabout because all of these different air masses all meet above the UK.

So there's lots of competing air masses.

But synoptic charts don't have arrows labelled on their maps in the same way that we can see here.

On synoptic charts, cold fronts are shown by a blue line with blue triangles on them.

We can remember this because the blue triangles look a little bit like icicles.

So that reminds us it's a cold front.

Now at the cold front, cold air pushes the warm air upwards.

This causes heavy frontal rain followed by falling temperatures as the colder air mass moves in.

Likewise, warm fronts are shown by a red line with red circles on.

And these are easy to remember because these look like half suns.

At the warm front, warm air rises over the cold air.

This causes drizzly frontal rain followed by rising temperatures as the warm air mass moves over the land.

And lastly on synoptic charts, we have occluded fronts, and these are shown by a purple line that has purple circles and triangles on it.

Now occluded fronts happen when the cold front catches up with the warm front, and there are sudden downpours of heavy rain.

So the synoptic chart below shows a number of different weather fronts, and we can see those by identifying where those different coloured lines are.

So here we have our blue line with the blue triangles on it, which represents our cold front.

Here we have the red line with red circles on it, representing the warm front.

And lastly we can see our purple line with the purple half circles and triangles on them, showing our occluded front.

Let's check your understanding so far.

So which synoptic chart below shows a cold front moving across the UK? Pause the video and have a go at completing this task.

Well done if you said B.

You can see the blue line with the blue triangles on is moving across the UK.

Good work geographers.

So you're now going to practise what you've learnt so far, and I'd like you to use the synoptic chart to write a weather forecast for London.

I'd like you to use the following words, pressure, isobars, front, synoptic chart.

Pause the video and have a go at completing this practise task.

Well done for giving that a really good go, geographers.

Let's see what your answer may have included.

So the synoptic chart suggests that London's weather might be changeable with some rain, winds and cloudy skies, but also calmer periods due to the nearby high pressure.

To the south of London, there is a high pressure system, and to the north there is a low pressure system.

There are also a warm front nearby and a cold front following.

The high pressure system is likely to bring stable conditions.

The nearby fronts suggest a chance of rain, especially as low pressure systems tend to bring unsettled weather.

Winds could be breezy as the isobars are fairly close together over the UK.

The fronts could also bring clouds.

Well done geographers.

I'm sure your weather forecast was absolutely spot on.

You've done a brilliant job today.

So to summarise from today's lesson, weather forecasts can be displayed on synoptic charts.

Air pressure is shown on weather maps by isobars, which indicate areas of equal air pressure.

Symbols are used to indicate the type of weather that can be expected.

And weather fronts are shown on weather forecasts, and these can include cold, warm and occluded fronts.

It was really brilliant to work with you today, geographers, and you've worked really, really hard.

I hope you have a lovely rest of your day and I'll see you soon for our next lesson.