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We will prepare the plot interactively using icons. Then, at the end, we will put it all together into a macro. Remember to give your icons useful names!

Steps

Setting the View

With a new Geographical View icon, set up a cylindrical projection with its area defined by its lower-left corner [20^oN, 110^oW] and its upper-right corner [70^oN, 30^oW].

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• the land coloured in cream
• the coastlines in grey
• the grid as a grey dashed line

Plotting the Mean Sea Level Pressure field

Plot the GRIB file msl.grib into this view using a new Contouring icon. Plot black isolines with an interval of 5 hPa between them. Since this will be plotted on top of another field, it would also be a good idea to increase the thickness of the isolines. Activate the legend in the Contouring icon and set the legend text for this icon to "MSLP".

Plotting the Precipitation Field

The GRIB file precip.grib contains a pre-processed field of precipitation accumulated over 3 hours before and after the time of the MSLP field (a total of 6 hours of precipitation).

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• use the following list of levels for contouring: 0.5, 2, 4, 10, 25, 50, 100, 250  (but remember that in the Contouring icon editor to use a forward slash to separate the items)
• use the following list of colours:  cyan, greenish_blue, blue, bluish_purple, magenta, orange, red, charcoal (use the Contour Shade Colour List helper tool)
• deactivate the contour highlight
• activate the legend

Overlaying Both Fields

Visualise your Geographical View icon and drop the following icons into the Display Window:

• your Coastlines icon
• the msl.grib icon with your MSLP Contouring icon
• the precip.grib icon with your precipitation Contouring icon

Improving the Legend

Create a new Legend icon and change Legend Display Type to Disjoint. Play with the font size and colour and set the legend title to say something about the precipitation field. Drop it into the Display Window to see the results.

Adding the Position of New York City

One easy way to add a place-mark is to use the Input Visualiser icon and combine it with a Symbol Plotting icon.

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Create a new Symbol Plotting icon to plot this as a red marker (the filled circle is marker index 28) with some text for its legend entry.

Adding a Custom Title

Using a Text Plotting icon, add a custom title as shown in the plot.

Generating a Macro to Reproduce the Plot

Generate a macro which will reproduce your plot with a single click. This can be done either by clicking the Generate Macro button from the Display Window or by editing a new Macro icon, dropping your data and visdef icons into it and adding a plot() command.

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