[gradsusr] Incorrect Winds from NCEP NAM file

[Rowell, Mason D.]

Don,

Did you build your grads with the appropriate environment variables such that it can handle grib2 data? There should be some documentation on compiling GrADS so that it handles grib2.

Mason 
________________________________________
From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] on behalf of Donald Van Dyke [Don.VanDyke at noaa.gov]
Sent: Thursday, October 27, 2011 5:33 PM
To: gradsusr at gradsusr.org
Subject: [gradsusr] Incorrect Winds from NCEP NAM file

Hello,

I'm not sure if this is a grib2 file problem or a GrADS problem, but if
I try to plot the winds from the attached NAM grib2 file from NCEP, the
wind is plotted incorrectly.  I am using g2ctl.pl with no flags and
gribmap -i to create the .ctl and .idx files.  In the GrADS script, I am
using simple commands such as

"set lev 250"
"d mag(ugrdprs,vgrdprs)*1.943844449"
"d skip(ugrdprs*1.943844449,2,2);skip(vgrdprs*1.943844449,2,2)"

The image created is attached along with an image from NCEP showing what
the winds should have looked like over my area in the Florida
Panhandle.  They're obviously not northerly.  I am currently using
grads.2.0.a9.  I have also attached the grib2 file as well as the .ctl
file and .idx file I created with g2ctl.pl and gribmap.  Thanks.

-Don