Marine Data Literacy 2.0

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Home > 9. Operational/Synoptic > 9.30 Cyclone Grids

9.30 Visualizing Gridded Tropical Cyclone Products in IDV: NHC

  • Exercise Title:  Visualizing Gridded Tropical Cyclone Products in IDV: National Hurricane Center (NHC)

  • Abstract:  This exercise and the companion vector-targeting exercise provide the user with mean to access and use the latest model results for the Atlantic and eastern Pacific from the US National Hurricane Center.  The product area covers all US possessions, from Guam to Maine, plus the typical hurricane path east to the west coast of Africa, and areas in the Pacific south to mid-Chile.  This exercise does not cover all of the typhoon-susceptible area of the Pacific.  Of particular technical interest are the steps here to set up a special new "projection" in IDV for these products, putting a spotlight on the general method involved.  THIS LESSON IS PROVIDED FOR EDUCATIONAL PURPOSES ONLY.  NO ONE SHOULD ATTEMPT TO RELY ON THESE ANALYSIS PRODUCTS FOR NAVIGATION OR FOR ANY OPERATIONAL PURPOSES AT SEA.

  • Preliminary Reading (in OceanTeacher, unless otherwise indicated):

  • Required Software:

  • Other Resources: 

  • Author:  Murray Brown

  • Version:  July 2013

1.  Open the NHC website, and spend some time reading through the massive amount of documentation for its important products and services.
2.  Midway down the left-hand menu, click on the GRIDDED MARINE item.
3.  This is the long menu for the gridded products. 
  • There is a graphical interface, where you can see the grids immediately, linked just beside the image. 
  • But we want the grids, located just below the graphical interface link.
4.  Scroll down to find this menu for grid product files.  Note that you can obtain grids for up to 6 days in the future, and both HTTP- and FTP-type links are available.
5.  You'll find links like these in any one of the 4 choices above.  Most of the BIN files are actually grids in GRB format.  [The WWA BIN file is GRB, but it is some sort of warning message that we can't use in IDV.]

For this exercise, click the HTTP 1-3 day link.


6.  Use normal procedures to make these SAVEs of the files:
  • Save ds.wspd.bin to windspeed_grid_YYYYMMDD_hurricane_center.grb - (make sure to use SAVE AS TYPE: ALL FILES to avoid a BIN extension on the filename; use same caution for the following 3 files)
  • Save ds.wdir.bin to wind_dir_grid_YYYYMMDD_hurricane_center.grb
  • Save ds.wgust.bin to wind_gust_grid_YYYYMMDD_hurricane_center.grb
  • Save ds.wavh.bin to wave_ht_grid_YYYYMMDD_hurricane_center.grb

Where YYYYMMDD is today's date in ISO format.


Before you can add any data, for the NHC GRB files in IDV you must make the following two changes..

8.  Uncheck the AUTO-SET PROJECTION function.
11.  Now in the IDV dashboard, use these settings to load the wind speed file.

Then click ADD SOURCE.

12.  Make these settings. Notice that you must set USE SELECTED to choose only a single date.  Then click CREATE DISPLAY.

NOTE:  If you want to make an animation, then select all the dates instead of just one date.

13.  Here's the first view of the data.  If it doesn't look this way, make sure you performed the steps in Panels 8-10.

The color palette is too restricted, as it only shows blue.  And it's not convenient to have the far western Pacific separated from the left side of the main map.  We can fix these things in the next few panels.

Look closely to see where a better map would have it limits.

15.  You'll see this master set of projections.  We want to make a new one that covers all of our grid, but not unnecessary areas.

Click on NEW (at top of menu).

16.  This is the projection editor.
17.  Enter a name for your new projection.  Then drag the corners of the map frame to cover the better limits you selected above (Panel 13).

Then click SAVE.

NOTE:  If the result doesn't look right, then you can return and use the EDIT control to make adjustments.

18.  Now click APPLY.
20.  And here's a much better map of the complete grid.

NOTE:  Many thanks to Yuan Ho at the IDV User Support Desk for the critical settings in Panels 8-10, that make this visualization possible.

21.  To fix the colors, select DISPLAYS > COLOR TABLE > RADAR > DbZ.

To fix the value range (currently 0-80!), select DISPLAYS > COLOR TABLE > CHANGE RANGE


Then click OK.

23.  This is the finished graphic for the windspeed file.  Notice in the bottom right corner that the range-change operation (above) resulted in a top speed of 18 m/sec. 

The forecast image is for the day of July 29.  Tropical Storm Dorian is easily visible eastward from Cuba.

NOTE: You could also plot the wind gust file to see the expected maximum values.  These are the physical factors that cause casualties and property damage, an important visualization.


24.  It would be a public service of great merit for the NHC to provide these data in a THREDDS server, or at least in an OPeNDAP architecture.  This would allow for automation of the images, and other more efficient usages.
25.  A FINAL WORD OF CAUTION.  If you are not a certified meteorologist, then do not use the above methods and products to "publish" or circulate tropical storm analyses as if they were your own invention.  Make certain that everything you make here is clearly identified by you as having come from a specific other source, namely the National Hurricane Center of the USA.  And be very careful that you date your files and products so that older version can be scrapped and do not cause problems.  These are wonderful data products and software systems, but they can easily be abused and cause difficulties if you do not take care to educate users about their origins and purposes.