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Sylvia’s solution

End of week tutorial
from the Royal Meteorological Society. And I’m going to go through some of the exercises that we left you to do in this week’s course. Hopefully you found that they made you think and interpret some of the things that you’ve read about or heard about in the course this week, and you found that that’s being quite helpful. So first of all, if we look at this weather map with a number of features that we asked you to identify on it. And the first thing to point out about this map is that unhelpfully, it does have North up here in the top left corner. So these are the lines of longitude, which go from north to south.
And you have to bear that in mind when you’re thinking about directions. But first of all, if we look at the fronts, hopefully you remembered that a cold front is anything with a triangle on it. So it could be this one or this one down here. Warm front is anything with semicircles on it. So this one or this one, maybe. An occluded front is something with triangles and semicircles on it.
So that was that. Next, if we look at the high and low pressure words– so depression is the same thing as a low-pressure system. It’s got a cross marking its centre, and an L and together, with the pressure value at the centre. So that would be an example of a low, so with that one there. On the other hand, an anticyclone is the same thing as a high pressure system. So that’s anything marked with an H. So maybe that one or that one, or this one at the bottom of the image.
Now if we look at winds, if you remember, the closer the pressure contours are to each other, than the windier it is. So the windiest place on this map is probably in this area here, where those pressure contours are very close to each other. Whereas the place with the lightest winds might be down here, where the pressure contours are really quite a long way apart.
Now, if we look at the direction of the winds, that’s a tricky bit. But if we think about this low pressure system here to start with, the winds are blowing round it in an anticlockwise direction. The winds follow those pressure contours, and we name winds by the direction they’re blowing from. So if we want a northwesterly wind, we want a wind that’s coming from the northwest towards the southeast. And one area where you might find it is down here, where the winds are cutting like this across the lines of longitude and latitude. So those are those northwesterlies down here. For northerly winds, we follow that round. So the winds here would be northeasterly.
And they’re turning into northerlies just in this area here. So you’ve got northerly winds around here. And for southwesterlies, they turn, they turn, they turn, they turn. They become southwesterly about here. So you’ve got the southwesterlies actually pretty much all in this area of the map. Coming onto the images now, that’s quite tricky. But this image D, first of all, that shows cirrus clouds, so clouds very high up in the atmosphere. And they’re the first indication that a warm front is coming. So you can find them in front of any warm front. So maybe in this area here.
C shows some nimbostratus clouds, so sheets of very dark low cloud and those are on a warm front. So on or just ahead of a warm front, you’ll find clouds like that. On the other hand, if you looked out the window in the morning and saw clouds like this, you’d probably think it was a fairly nice day. So those are cumulus clouds. They’re little cumulus clouds, little puffy clouds. Got nothing to do with a depression at all. So you might find those anywhere that’s far away from any of these fronts.
On the other hand, A shows a cumulonimbus cloud, so a towering great big thunder cloud, and that’s the sort of thing that you might find on a cold front for a cloud like that.
Moving onto the next exercise, which is asking you to consider what the weather’s like at different places. And this map, first of all, from the 5th of July. And if we look at it, there’s no fronts near any of these places, Where the pressure contours are very far apart from each other, so the winds are really light. There’s high pressure there, so the wind’s blowing around here in a clockwise direction. So the winds are blowing along these contours like that. So we’ve got easterlies in Exeter and in Norwich, more like southerlies in Glasgow. But the winds are very, very light. There’s no fronts or anything near these places. So clear skies, sunshine and in Glasgow and Norwich.
Exeter, on the other hand, is close to this very little low. It’s only slightly lower pressure than the pressure around it, so there’s not very much going on. But that might be enough of a low pressure to give you a little bit of cloud. Going onto the next image– and you can see that we have got a depression in this image, affecting our places. But whereas Aberdeen is quite a long way ahead of the warm front, so it might be beginning to cloud over, but you wouldn’t expect too much in the form of rain there. You’ve got London, though, is right on the warm front, so it’s going to be raining quite persistently there.
Galway, on the other hand, is behind the cold front, so the skies might be clear. You might have the odd shower or the odd cloud, but on the whole, the skies are clear there. The pressure contours are quiet close to each other. So it’s quite windy everywhere on this map. And the wind direction goes from slightly a north of westerly into a southwesterly in London, and then pretty much a southerly wind up in Aberdeen.
The 16th of January one, again, we’ve got a low-pressure system here, and all three places are in the warm sector between the fronts. Norwich, first of all, is quite a long way out. It’s quite a way from any of the fronts, it’s quite a way from the centre of the low. So you might have sunny intervals there. You might have some light rain but on the whole, it’s not too bad. Carlisle, on the other front, is going to be a lot more overcast. It’s closer to the front, it’s closer to the centre of the Depression. So you might have some light rain there. Tiree, on the other hand, you’re very close to the cold front.
So the rain is going to be much heavier. You’ve got cumulonimbus thunderclouds above you. You might have some thunder and lighting, definitely heavy rain. Much of the worst weather at Tiree, on this weather map. And in terms of the wind direction, you’ve got wind blowing around the low-pressure system in an anticlockwise direction. So the wind direction is going to be a southwesterly at all of those places. And then lastly, if we look at the 13 of January map, we’ve got Tiree, and Leeds and Brighton. Tiree’s right on the warm front. So that’s going to have thick cloud and rain, and pretty strong southerly winds now. Leeds, on the other hand, is ahead of the warm front.
It might be beginning to get cloudy, but it certainly won’t be raining yet. And you’ve got a southerly, southwesterly wind there at Leeds. Whereas at Brighton, you’re a long way away from the depression, really. There’s not going to be any fronts or anything affecting the weather at Brighton. It’s going to be sunny, it’s January, so it’s not going to be particularly warm. But the wind is lighter. Those pressure contours are further apart. It’s still a southwesterly, but the wind’s going to be lighter than it is at either of the other places.

Join Sylvia to find out how you got on this week.

In this film Sylvia demonstrates the solutions to the weather map exercises in the previous two Steps, and explains how she arrives at each answer. Although the graphics used in the film are slightly different from the ones you were given, without the annotated numbers, the explanations should still be helpful.

We have also provided the solutions for the exercise in Step 1.15 on a PDF sheet for you to download and print.

How did you do? If you still have questions or would like further guidance on the topics covered, follow Sylvia, Pete and our course mentor, Liam, and check to see if they have provided the answer to another learner already.

Alternatively, please ask your question in the comments area in this Step. Although we won’t be able to answer every learner directly we’ll try to identify the most common questions and address these. You can also ‘Like’ another learners question to help us identify any particularly challenging areas.

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Come Rain or Shine: Understanding the Weather

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