• 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):

  • Tropical Cyclone/Hurricane - Wikipedia article

• Required Software:

  • Integrated Data Viewer (IDV)

• Other Resources: 

  • US National Hurricane Center (NHC)

    • Gridded Marine - NHC page for these gridded products

  • 9.14 Plotting Atlantic and Eastern Pacific Tropical  Cyclone Paths in IDV: NHC - Parallel exercise covering a bit more than the areas covered here

  • 9.32 Plotting Western Pacific/Indian Ocean Typhoon Paths in Google Earth & IDV: JTWC - Parallel exercise covering a part of the areas covered here

• Author:  Murray Brown

• Version:  July 2013

• 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.

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

• 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..

Then click ADD SOURCE.

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

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.

Click on NEW (at top of menu).

Then click SAVE.

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

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.

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

Then click OK.

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.