[gradsusr] NAM 12km vs. NAM Conus Nest Wind Direction

[Jeff Duda]

Sam,
I'm not really sure what's the deal with the wind vectors. Maybe it's a
temporary error that needs to be fleshed out still.

But in the meantime, i have a suggestion: instead of going through all the
effort to convert from grib2 to grib1, just use g2ctl to generate a control
file for the grib2 data. Grads is perfectly capable of reading grib2 data.

g2ctl is just like grib2ctl.pl except it works for grib2 files. A quick
Google search will reveal where you can get it.

Jeff Duda

On Thu, Mar 23, 2017 at 10:31 AM, Sam Wilson <sam at surfline.com> wrote:

> Just to add some detail here on how I’m processing the data from both the
> NAM 12km and the NAM conus nest:
>
>
>
> After downloading the grib2 files, I run the following:
>
>
>
> Wgrib2 grib2file –grib tmpgrib2file
>
> Cnvgrib –g21 tmpgrib2file grib1file
>
>
>
> I then run the grib2ctl program on the grib1 file to produce the ctl file.
>
>
>
> The wgrib2 version I’m using is v0.1.9.7a.
>
>
>
> Thanks
>
> Sam
>
>
>
>
>
> *From: *<gradsusr-bounces at gradsusr.org> on behalf of Sam Wilson <
> sam at surfline.com>
> *Reply-To: *GrADS Users Forum <gradsusr at gradsusr.org>
> *Date: *Thursday, March 23, 2017 at 8:05 AM
> *To: *"gradsusr at gradsusr.org" <gradsusr at gradsusr.org>
> *Subject: *[gradsusr] NAM 12km vs. NAM Conus Nest Wind Direction
>
>
>
> This sender failed our fraud detection checks and may not
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> Hi all,
>
>
>
> After the recent upgrade of the high resolution NAM conus nest, the wind
> direction in the wind plots I make appears to be wrong.
>
>
>
> I also plot wind data from the NAM 12km data – below are the PDEF, XDEF,
> and YDEF lines from a NAM 12km ctl file and a NAM conus nest ctl file:
>
>
>
> NAM 12km:
>
>
>
> pdef 614 428 lccr 12.190000 226.541000 1 1 25.000000 25.000000 265.000000
> 12191 12191
>
> xdef 614 linear -133.459 0.113383763365335
>
> ydef 428 linear 12.190000 0.110827272727273
>
>
>
> NAM conus nest:
>
>
>
> pdef 1799 1059 lccr 21.138000 237.280000 1 1 38.500000 38.500000
> 262.500000 3000 3000
>
> xdef 1799 linear -122.72 0.0292401642786411
>
> ydef 1059 linear 21.138000 0.0272727272727273
>
>
>
> The NAM conus nest wind directions appear to be about 90 degrees offset
> from those of the NAM 12km.  I initially thought it may be an issue where
> one is using grid relative where another is using earth relative, but now
> I’m second guessing that – I ran wgrib2 on a single file from each with the
> -vector_dir option and both appear to show grid relative.. and as you can
> see above, both have “lccr” in the PDEF.
>
>
>
> What I’m after is being able to plot wind barbs in the meteorological
> convention from both and I’m curious why I’m getting different results
> between the above two datasets when plotting the same way.
>
>
>
> Many thanks!
>
>
>
> Sam Wilson
>
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-- 
Jeff Duda
Post-doctoral research fellow
University of Oklahoma School of Meteorology
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