fwrite help

[Mark Sponsler]

Hi Grads Users,

I'm trying to use fwrite to parse out a subset of data from a wavewatch3
grib. Pretty basic stuff. The fwrite function appears to work OK, but am
unable to generate a ctl file from that new dataset using grb2ctl.  Or if
manually generating the ctl file, I cannot get gribmap to construct an
index file.  I'm using grads v1.8SL11 on Windows.

Here's how I enabled fwrite:

  'open nww3all.ctl'
  'set t 1'
  'set y 1 157'
  'set x 1 288'
  'set z 1'
  'set fwrite grads.fwrite'
  'set gxout fwrite'
  'd htsgwsfc'
  'd dirpwsfc'
  'disable fwrite'

The grads fwrite file was generated with 354 KB of data in it.

Then I tried to build the ctl file:

  grb2ctl.pl grads.fwrite > grads.fwrite.ctl

Received Error:  Big Problem   Either grads.fwrite is missing or not a grib
file.

Here's the ctl file for the source data:

dset c:\grib\input\nww3.all.grb
index c:\grib\input\nww3.all.grb.idx
undef 9.999E+20
title c:\grib\input\nww3.all.grb
*  produced by grib2ctl v0.9.12.5p33e
dtype grib 233
options yrev
ydef 157 linear -78.000000 1
xdef 288 linear 0.000000 1.250000
tdef 51 linear 18Z12nov2004 03hr
zdef 1 linear 1 1
vars 11
DIRPWsfc  0 107,1,1  ** surface Primary wave direction [deg]
DIRSWsfc  0 109,1,1  ** surface Secondary wave direction [deg]
HTSGWsfc  0 100,1,1  ** surface Sig height of wind waves and swell [m]
PERPWsfc  0 108,1,1  ** surface Primary wave mean period [s]
PERSWsfc  0 110,1,1  ** surface Secondary wave mean period [s]
UGRDsfc  0 33,1,1  ** surface u wind [m/s]
VGRDsfc  0 34,1,1  ** surface v wind [m/s]
WDIRsfc  0 31,1,1  ** surface Wind direction [deg]
WINDsfc  0 32,1,1  ** surface Wind speed [m/s]
WVDIRsfc  0 101,1,1  ** surface Direction of wind waves [deg]
WVPERsfc  0 103,1,1  ** surface Mean period of wind waves [s]
ENDVARS

Do you have any ideas what is wrong?

Thanks in advance for your help.