clc;
sdfopen E:\Grads\win32\Data\slp.2004.nc
'set lon '
'set lat '
'set time '
'set lev'

'R=6.37e6'                             
'D2R=(3.1415/180)'
'ro=1.2'

'dx=cdiff(lon,x)*R*D2R*cos(lat*D2r)'  
'dy=cdiff(lat,y)*R*D2R'

'dpx=cdiff(slp,x)'
'dpy=cdiff(slp,y)'

'pgx=(-1/ro)*(dpx/dx)'                         
'pgy=(-1/ro)*(dpy/dy)'       
'd pgx;pgy'
c
'set gxout shaded'
'd slp/100'
'd  pgx;pgy'

'set gxout contour'
'd slp/100'
'run cbar'
c

%how much vector wind in the 1 oclock 

d mag(pgx,pgy)*3600
set gxout shaded

d mag(pgx,pgy)*3600
set gxout contour

d mag(pgx,pgy)*3600
run cbar