20021127: Unidata gribdec.tar.Z bundle (cont.)

>From: "HOETH, BRIAN R. (JSC-ZS) (LM)" <address@hidden>
>Organization: JSFC
>Keywords: 200211192250.gAJMoQ427093 McIDAS gribdec gbtbpds001.bv1

Brian,

>I can't even tell you how much I appreciate all this help!!  Well, we're
>almost there.

When I sent you the note yesterday, I had not had a chance to look at
the problem in decoding forecasts past 256 hours.  I will try to get
to that today.

>I made the changes you suggested and the pressure fields look good.  

Super.  Did you verify that GRDDISP has problems in plotting over certain
maps?  This really is a bug in GRDDISP.

>Compare the 00Z GFS run, forecast hour 6:
>http://www.srh.noaa.gov/smg/GFS00ZFHR06.GIF
>
>With the surface analysis from 6Z:
>http://www.srh.noaa.gov/smg/SFCANAL06Z.GIF

The pressures look good, but the winds are off.

>As you can see, the pressure patterns match up well.  As you can probably
>also see though, the wind fields don't match at all?  What I plotted for the
>GFS was the 10 meter winds ... well, I THOUGHT I was plotting 10 meter
>winds?  Here's what I entered:
>
>GRDDISP RTNEW/GFS TIME=6 FHOUR=0 PAR=WINDB LEV=10[M] PINT=2 NAV=C COLOR=4
>
>Even though the plot labels the winds as 10 meter winds, they are clearly
>not 10 meter winds.  They seem to be the 10 MB winds instead.  The GRDDISP
>command seems to just ignore my [M] units for the LEV keyword?  What's even
>stranger is that when I do a:
>
>GRDLIST RTNEW/GFS TIME=6 FHOUR=0 PAR=WINDB LEV=10[M] NUM=ALL
>
>I get the grid listed back?

Here is what I got for the 0Z run, 15 hour forecast from yesterday:

GRDLIST MYDATA/GRIDS.6010 TIME=0 FHOUR=15 PAR=WINDB LEV=10[M] NUM=ALL
Dataset position 6010   Directory Title=
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
U      10 M    26 NOV 02330 00:00:00  AVN    15 26 NOV 02330 15:00:00   293 MERC
V      10 MB   26 NOV 02330 00:00:00  AVN    15 26 NOV 02330 15:00:00   200 MERC
Number of grids listed = 2
GRDLIST - done

Notice how the 10 m U component was found, but the V component is for
10 mb.  This is probably where the problem lies.  GRDDISP may correctly
setup the search conditions for the first component, but not the
second.  This would then give us very strange winds indeed.

To test if that was, in fact, the problem, I did the following:

DSSERVE ADD G/G GRID 1 9999 TYPE=GRID "ALL LOCAL GRID FILES
Adding the group G as a local dataset

Group/Descriptor         Type  Format & Range     RT Comment
------------------------ ----- ------------------ -- --------------------
G/G                      GRID  GRID 1-9999           ALL LOCAL GRID FILES
DSSERVE: done
 
GRDCOPY MYDATA/GRIDS.6010 G/G.1 PAR=U LEV=10[M]
Total grids copied=1
GRDCOPY - done
 
GRDCOPY MYDATA/GRIDS.6010 G/G.1 PAR=V LEV=10[M]
Total grids copied=1
GRDCOPY - done

GRDLIST G/G.1 NUM=ALL
Dataset position 1      Directory Title=
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
U      10 M    26 NOV 02330 00:00:00  AVN    15 26 NOV 02330 15:00:00     1 MERC
V      10 M    26 NOV 02330 00:00:00  AVN    15 26 NOV 02330 15:00:00     2 MERC
Number of grids listed = 2
GRDLIST - done

GRDDISP G/G.1 PAR=WINDB LEV=10[M] NAV=C PINT=2
GRDDISP: Done with graphic frame 11

Sure enough, the plot matched what I expected for near surface level winds.
So, I would venture to say that the problem is the mis-selection of the
V grid component when sepecifying a particular level by the GRD* programs.

>Needless to say, at this point I think these
>troubles that I'm having now are McIDAS bugs and thus probably require an
>inquiry to SSEC?

This one really does deserve an inquiry.

We can probably get away with plotting 1000 MB winds for
>now to do our analyses?

I would say to copy the 10 m U and V wind components to a scratch GRID
file where you are sure that there are no other 10 MB/M winds and then
do the GRDDISP from it.

>Thanks a million!! (guess you'll have to settle for beer offerings cuz I
>ain't got a cool mill in the bank just yet).

I will be looking into the decoding past 256 hours sometime today (I hope).
If I find something, I will send you a note.

By the way, I did see that there were a number of levels in the 1 degree
AVN file that were not recognized.  I believe you said that you added
definitions for those levels?  If so, can you send me the routine you
modified so I can fold those additions into the gribdec.tar.Z bundle?
Thanks.

Tom