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zyGrib Quickstart


Getting data

After launching the program you will be presented with a map of the world. No GRIB weather forecast data is shipped with this disc, you’ll have to download some, which will require an internet connection. As GRIB data is often used by offshore sailors, a number of low-bandwidth email and radio-modem services are available for those without a steady internet connection. i.e. while requiring some connection to the outside world as a data source, this connection is not required at run-time unlike many other web mapping programs.

You may get GRIB data from many sources, but as a convenience the zyGrib authors maintain a data server. The first thing to do is to check that the connection to the server is operational. Click on the power plug icon near the right hand end of the toolbar, after a moment it should tell you that the connection is ok.

We are usually interested in local weather conditions, so next left-mouse click drag a box on the map canvas on a part of the world you are interested in. The Gulf of Mexico or the southern tip of Africa often have dynamic winds. With your box drawn on the map click the zoom-to-box icon on the taskbar (the magnifying glass with a small box underneath it), and again mark out a box of interest with a left-click drag, but this time covering most or all of the zoomed-in map canvas.

Now select File ‣ Download GRIB and select the features you want to download. If in doubt the defaults are ok. When ready click the Download GRIB file button at the bottom, and save the file to disk.

All going well you should now see a weather map with a time slider along the bottom, set for right now. You can use the mouse wheel to zoom in if you like.

Changing views

By moving the mouse around the map you’ll see the exact conditions under the cursor listed in the pane on the left.

You can change the time by moving the slider along the bottom, or from the drop down menu in the top-left of the window.

From the Data menu you can select the variable to visualize. For example Select Data ‣ Cloud Cover and the view should change.

If you downloaded data for the Gulf of Mexico you’ll be interested to view the CAPE data. “CAPE” stands for Convective Available Potential Energy at ground level. It is a measure of atmospheric instability, and high values (1000s of J/kg) indicate a threat of thunderstorms and/or tornadoes.

If you downloaded data for southern Africa cloud cover may be more interesting.

Creating an animation

When you click the right-hand most icon on the toolbar (a rocketship) a new window will open and an animation will be generated. Sit tight while it runs through the time sequence for the first time. When it is done it will rewind to the beginning of the time series, and from there you can play, pause, rewind as you like. You can also save each frame as an image file for later encoding into an AVI, MPEG, or animated GIF using other software.

When you’re done click the red power button to close.

See also

The OpenCPN software (also on this disc) has a GRIB overlay plugin which you may try with your newly downloaded GRIB file. See the OpenCPN quickstart for details.

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