Step One – A Fertile Question

It’s only in the last couple of years that I have finally arrived at the lesson on hurricane formation that I am happy to deliver. Sure, cross sections where students can identify the features and the pre-requisites for their formation are fine, but I wanted to delve deeper. I want students to know the genesis of a hurricane from its humble beginnings as a series of small thunderstorms in equatorial Africa to the phenomenal hurricanes that news stations are so happy to send reporters out in to. To begin, I ask what Mark Enser would term a fertile question – ‘Why is the United States interested in thunderstorms in Africa?’

Step Two – Planning the Page

Again, I would always suggest using a student exercise book to plan out drawings and explanations. You then know what will fit on a page (even for the student who has massive writing). I’ve decided that a birds-eye and cross sectional view are to be used as between them I show all the intricacies and features a hurricane has. I’ve decided to use a page and utilise the margin as my equator for the birds-eye view and have the cross sectional view above.

Step Three – Planning Stages

I’ve decided that five stages, from thunderstorms in Africa to the dissipation of the hurricane over the Southern States of the USA, will allow for sufficient understanding and not over-complicate the delivery. Every stage is drawn out over the whole page so that I can see what a student book will look like at the end. It also allows me to judge the size of drawings and how much detail I can show as well as the space I can devote to explanation.

I would draw the birds-eye view first then follow this with the cross-sectional view. I would then spend some time explaining drawings and would be questioning them as to why thunderstorms would be forming here before writing down the brief notes to explain the diagrams.

Step 4 – Thunderstorms over Africa

The key points I would want students to know are:

• Maximum insolation due to curvature of the Earth causes rapidly rising air and the formation of thunderstorms.
• The absence of shear winds in the upper atmosphere means that the thunderstorms are not broken up.
• Easterly winds move the thunderstorms out into the Atlantic.

The second section involves drawing one enlarged thunderstorm out at sea, both in birds-eye and cross-sectional view.

Step 5 – Agglomeration

Again, the drawings would be explained and I would want students to know:

• Easterly winds have moved the thunderstorms out into the Atlantic.
• The absence of shear winds means that the thunderstorms haven’t broken up.
• The warm (greater than 26.5 degree Celsius) and deep (greater than 50m depth) ocean water fuels the thunderstorm further.
• The rapidly rising air condenses and releases heat, which further fuels that thunderstorm and causes the increased size.

The third stage then introduces spinning. Both the birds-eye view and cross-sectional view illustrate the thunderstorm increasing in size. The birds-eye view adds to this by showing the thunderstorm path moving away from the equator, which causes the spinning.

Step 6 – Spinning Around

From the drawings and explantion I would want students to know:

• The thunderstorm has increased in size as it is being fuelled by warm, deep oceans and heat released by condensation.
• The thunderstorm starts to spin anti-clockwise as it moves away from the equator in the northern hemisphere.

The fourth stage introduces the typical cross-section of a hurricane as well a birds-eye view that shows the spin direction as well as the eye and eye wall. This is the section that is the most complicated to draw so I would spend a but of time on this.

Step 7 – Cells

From the drawings and explanation I would want students to know:

• The energy of the thunderstorm has now caused wind speeds to exceed that needed for it to be classed as a hurricane.
• The thunderstorm has increased in size to the extent that there is now bands of warm, rising air and cold, descending air creating bands of cumulonimbus clouds.
• The centre of the hurricane has an eye where cold air quickly descends causing an eye of cloudless sky.
• The eye is surrounded by a rotating spiral of rapidly rising warm air, called the eye wall.

The final step shows the dissipation of the hurricane and its return to a thunderstorm over land.

Step 8 – Dissipation

Again, this would be explained and students would be expected to know the causes of hurricane dissipation, which came up as an exam question a few years ago in an AQA GCSE exam:

• Hurricane moves over land and is no longer being fueled by warm, deep oceans.

So, that’s how I explain the formation of hurricanes. This, like with all explanations I draw, is something that I will revisit each year and develop. Let me know what you think and if it’s been of any help.

Following on from @GeographyTom9‘s outline of how he teaches the Global Curculation Model, I thought i’d have a go at explaining how I teach about biome distribution.

Step One – Find a spare exercise book (or two)

I’ve found that when i’m drawing an explanation using my visualiser the best results always come from when I use an exercise book that is exactly the same size and those used by the class in front of my. This means I can guide their drawings and explanations and lay it out exactly as I have done. Ideally, two books are better than one as you can have your pre-planned drawings by your side as you re-draw them with the class in another book.

Step Two – Plan your drawings and explanations before delivering it in front of a class

This has been learnt from bitter experience. Drawing or writing down a half-baked explanation which requires continual editing and scrambles for rubbers (or a new page for those that never seem to use a pencil) will be avoided if your drawing and explanation (including edits) are planned in advance. In addition, it allows you the time and space to consider your explanations and whether they are clear and concise enough and whether your drawings need any more or less detail.

Step Three – Explaining latitude

With my pre-planned explanation in front of me I use a protractor and draw round the whole 180 degrees. I explicitly instruct students to draw their semi-circle with the 0 degree line on a line in their book so that this becomes the equator. The equator is then drawn on and labelled as 0 degrees and then 90 degrees north and south are also labelled as the most straightforward latitudes. After this, I then add on the Tropics of Cancer and Capricorn and Newcastle-upon-Tyne to show how north we are.

Step Four – Insolation

After latitude, I explain insolation. Again, drawing the equator on a line in the book helps as I use one full line north and south of this to indicate insolation at the equator. I then instruct the students to draw a line of equal thickess at the top (the last two complete lines before the north pole). This allows me then to explain how the curvature of the Earth increases the surface area heated by the same amount of insolation and therefore how latitude affects temperatures. This is also a good time to check for the common misconception that distance from the sun affects temperatures.

Step Five – Global Atmospheric Circulation

My explanation of rainfall explains global atmospheric circulation. This must come after latitude and temperatures as the main driver of the Hadley Cell is insolation at the equator. In order to explain global atmospheric circulation (not done that differently from @GeographyTom9) I start by looking at what happens to air heated by maximum insoaltion at the equator then take it from there to explain that rising warm air causes cooling and condensation that leads to rainfall and that sinking cold air doesn’t cause rainfall as there is no condensation. This allows me to then highlight that rainfall isn’t as straightforward as temperature and that it moves in bands of high and low rainfall from the equator to the poles. A small, but important, point here is that the size of each atmospheric cell is drawn to the size required to fit with the first drawing of latitude and the final drawing of biomes. This means that the descending cold air of the Hadley Cell aligns with the Tropics and the desert biome.

Step Six – Latitude, Temperature, Rainfall and Biomes

The final drawing has the equator and the tropics drawn on it, but nothing beyond that. This is where a vivid array of colors come in handy to mark the biomes. As this is drawn and explained the two previous diagrams outlining temperature and rainfall and constantly referred to to explain biome distribution, e.g. the desert biome is located at the tropics where there is little rainfall due to descending cold air and not clouds. This means no rainfall and the ground being heated intensely due to limited cloud cover. I have, recently, added a side bar to the final diagram that gives an overview of temperature and rainfall by the side of biome distribution to aid the explanation and overall understanding.

After this, I do some short answer exam questions to check understanding. That’s it.

Next time: I’ll find my notes on explaining hurricane formation over a double page spread from Africa to the Caribbean.