20040116: Computation of NSHARP parameters

>From: Kurt Buffalo <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200401162156.i0GLuDp2009126

>Hello,
>
>I'm a graduate student at Texas A&M University and I'm using NSHARP for 
>some of my M.S. thesis work.  I'm looking for some documentation on how 
>the various parameters output by NSHARP are computed.  I would greatly 
>appreciate it if you could point me towards any such documentation.  In 
>particular, I'm most interested in how the storm motion is computed.  
>
>Thanks,
>Kurt Buffalo
>
>

Kurt,
Since NSHARP was developed as an external application at the NSSFC,
the documentation available on it is less than the core GEMPAK
libraries. I believe your answer lies in the code:
$NAWIPS/nprogs/nsharp/source/xwvid6.c

Here the code shows in several locations the calculation
of st_dir and st_spd (storm motion components) as:
     mean_wind( sndg[sfc()][1], i_pres(msl(6000.0F)), &ix1, &ix2, &st_dir, 
&st_spd);
     st_spd *= .75F;
     st_dir += 30.0F;
     if(st_dir>360.0F) st_dir -= 360.0F;
     printf( "storm motion = %f/%f\n", st_dir, st_spd);

This calculates the mean wind in the sfc to 6000m layer,
and then adjusts the speed by 75% and adds a 30 degree (eg Ekman)
component to the wind. The code doesn't have a reference to this 
calculation, so I would suggest looking at relevant liturature and
the SPC as well.

Steve Chiswell

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