How to install rNOMADS with GRIB file support on Windows

Two years ago, I wrote a software package for R called “rNOMADS” that interfaces with online weather and sea ice model repositories to gather data in real time, for free.  The data are delivered in two ways: a simple, pure R, cross platform interface using GrADS-DODS, and binary files in GRIB format.  The one issue with GRIB is that this format can’t be read directly into R; it requires the external program “wgrib2.”  Installing rNOMADS with GRIB support for Linux is covered in this post (Mac OS is probably similar).  I thought GRIB support for Windows was impossible until the guy who runs this blog casually told me he’d figured it out.  So, I finally got around to trying it myself, and I’m happy to say I got it to work!  Here’s how:

Step 1:

Download the most recent wgrib2.exe version and all DLL files from Wesley Ebisuzaki’s web site:  Click here.

Step 2:

Make a directory somewhere on your computer.   I chose:  C:Program Fileswgrib2

Copy the .exe and the .dll files to this directory.

Step 3:

Append the directory path to the Windows PATH variable.  Find out how to do this here.

Step 4:  If R is open, close and reopen it.  Then try the following command in the R interpreter: system("wgrib2")

If you get a bunch of text that looks like the image below, you’ve succeeded.  You can start reading GRIB files with rNOMADS!

Output of wgrib2 call from R.