Re: [gembud] WPC winter probabilities

Hi Russ,

There are a couple reasons why these products are not being decoded; one is 
simple to fix, the other, a bit more challenging.

First, the $GEMTBL/grid/g2varswmo2.tbl needs to have an entry added for this 
type of GRIB2 product:

000 001 029 009 P of Snow Exceeding Amount       %                    SN        
       0   -9999.00

Second, the function that builds the string for the GEMPAK parameter name needs 
to be rewritten to handle the case when the value of the target amount (in this 
case, .0254 meters + multiples thereof) gets translated into a string that has 
too many leading zeroes, causing the GEMPAK parameter names to not be unique 
for each target amount.

I'm sure there is a cleaner way to do this, but I simply added a scale factor 
test in the function in the file $GEMPAK/source/griblib/gb/gb2prob.c:

25d24
<  * K. Tyle/UAlbany      11/13 Updated case 1 sprintf format           *
55,60d53
< /*
<  *            Special Case if scale factor results in a number
<  *            too large to fit in param string
<  */
<                   if (scale < -2.0 ) sfact= 1.0;
<                      

To get this incorporated into NAGRIB2, after you edit gb2prob.c in the 
$GEMPAK/source/griblib/gb directory, do the following:

Type make (this will build the gb2prob.o file)
Type ar rv $GEMLIB/gemlib.a gb2prob.o (this will update the gemlib.a library 
archive)
cd to $GEMPAK/source/programs/na/nagrib2
Type make clean install

Then give it a try!!

I've attached the two files.  Maybe Michael @ Unidata or Scott @ NCEP can 
determine a better method.
My work is all based on the GEMPAK6.10 package, but suspect it will work for 
earlier versions of GEMPAK 6 as well.

--Kevin

_____________________________________________
Kevin Tyle, Systems Administrator 
Dept. of Atmospheric & Environmental Sciences   
University at Albany
Earth Science 235, 1400 Washington Avenue                        
Albany, NY 12222
Email: ktyle@xxxxxxxxxx
Phone: 518-442-4578                             
_____________________________________________


-----Original Message-----
From: gembud-bounces@xxxxxxxxxxxxxxxx [mailto:gembud-bounces@xxxxxxxxxxxxxxxx] 
On Behalf Of Russ Schumacher
Sent: Wednesday, November 20, 2013 11:37 PM
To: gembud@xxxxxxxxxxxxxxxx
Subject: [gembud] WPC winter probabilities

Hey gembuds,

Has anyone successfully decoded the WPC winter precip probability GRIB files, 
which are located here: ftp://ftp.hpc.ncep.noaa.gov/pwpf/conus/pwpf_24hr/ ?

When running them through NAGRIB2 I get the following errors:

 [GB 1]  No GEMPAK parameter name defined for this grid.
 [GB -34]  Could not convert GRIB2 message to GEMPAK grid.


The GRIB2 messages looks like this, which I realize probably doesn't convert in 
a straightforward way to a GEMPAK field name: 
1:0:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.0254 
2:23442:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.0508 
3:41685:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.1016 
4:52983:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.1524 
5:60796:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.2032 
6:65559:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.3048 
7:67086:d=2013112100:ASNOW:surface:CodeTable 4.11=missing:prob >0.4572


If there's an easy way to decode these, I'd appreciate you sending it along 
(but if not, it's not a huge deal -- the WPC's web graphics for these products 
are very nice.)  Thanks!

Russ





--
Russ S. Schumacher
Assistant Professor
Department of Atmospheric Science
Colorado State University
e-mail: russ.schumacher@xxxxxxxxxxxxx
phone: 970.491.8084


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#include "gb2def.h"

void gb2_prob( gribfield *gfld, char *param )
/************************************************************************
 * gb2_prob                                                             *
 *                                                                      *
 * This function adds probability info to the GEMPAK parameter string.  *
 *                                                                      *
 * gb2_prob( gfld, param )                                              *
 *                                                                      *
 * Input parameters:                                                    *
 *      *gfld           struct gribfield        Decoded GRIB2 structure *
 *                                                                      *
 * Input/Output parameters:                                             *
 *      *param          char            GEMPAK Parameter string         *
 **                                                                     *
 * Log:                                                                 *
 * D.W.Plummer/NCEP      2/96   New                                     *
 * M. Linda/GSC         10/97   Corrected the prologue format           *
 * S. Jacobs/NCEP       12/00   Added prototypes                        *
 * S. Gilbert/NCEP      12/04   Modified from gbensemble.c for use w/   *
 *                              GRIB2                                   *
 * S. Gilbert/NCEP      10/05   Corrected overwrite error w/ param name *
 * S. Chiswell/Unidata   4/07   Updated case 2 sprintf format           *
 * K. Tyle/UAlbany      11/13   Updated case 1 sprintf format           *
 ***********************************************************************/
{
    int prob_type;
    float       lower, upper;
    double    scale,sfact;
    char        cpds[32];
    int ext_flag, num;

/*---------------------------------------------------------------------*/

    ext_flag = 0;
    cpds[0] = '\0';

    switch ( gfld->ipdtnum ) {

        case  5 :               /* Probability fcst */
        case  9 :               /* Probability fcst */
            ext_flag = 1;
            prob_type = gfld->ipdtmpl[17];
            switch (prob_type) {
                case 0 :
                    scale= (double)(-1.0*gfld->ipdtmpl[18]);
                    sfact= pow((double)10.0,scale);
                    lower = (float)(gfld->ipdtmpl[19]) * sfact;
                    sprintf( cpds, "%04dPB", (int) lower );
                    break;
                case 1 :
                    scale= (double)(-1.0*gfld->ipdtmpl[20]);
                    sfact= pow((double)10.0,scale);
/*              
 *              Special Case if scale factor results in a number
 *              too large to fit in param string
 */
                    if (scale < -2.0 ) sfact= 1.0;
                       
                    upper = (float)(gfld->ipdtmpl[21]) * sfact;
                    sprintf( cpds, "%04dPA", (int) upper );
                    break;
                case 2 :
                    scale= (double)(-1.0*gfld->ipdtmpl[18]);
                    sfact= pow((double)10.0,scale);
                    lower = (float)(gfld->ipdtmpl[19]) * sfact;
                    scale= (double)(-1.0*gfld->ipdtmpl[20]);
                    sfact= pow((double)10.0,scale);
                    upper = (float)(gfld->ipdtmpl[21]) * sfact;
                    sprintf( cpds, "%04d%04d", (int) lower, (int) upper );
                    break;
            }
            break;
    }
    if ( ext_flag == 1 ) {
        num = 12 - strlen(param);
        strncat ( param, cpds, (size_t)num );
    }
    return;
}

Attachment: g2varswmo2.tbl
Description: g2varswmo2.tbl