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Re: [netcdf-java] Decoding NDFD Severe Weather product Problem

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  • Subject: Re: [netcdf-java] Decoding NDFD Severe Weather product Problem
  • Date: Thu, 06 Jan 2011 14:48:27 -0700
On 1/5/2011 1:18 PM, Jeff Brogden wrote:

John Caron wrote:

On 1/4/2011 9:12 AM, Jeff Brogden wrote:

John Caron wrote:

On 1/4/2011 8:24 AM, Jeff Brogden wrote:

Hello,
I have successfully used netcdf-java to open NDFD products as a GridDataset. The problem I'm having is that the Severe Weather products use the local use section of the GRIB2 message to embed a weather string table that is used to create the "colorbar" or legend for that product. 

From the NDFD website.
"Cell values in the data part of the GRIB2 message are numbers which refer to the entry in the weather string table."
How do I read the local use section out of the GridDataset formated GRIB2 data so I can use it to build a proper legend from the data? 

Any help would be appreciated.  Thank you.


Hi Jeff:
Can you send me a sample GRIB record that has a local use section. thanks 

john
Sure, see attached. Using the degrib utility NDFD provides, the local use section should contain: 
Number of Elements in Section 2 | 17
Elem   0  Is Used | <None>
Elem   1  Is Used | SC.Y
Elem   2  Is Used | WI.Y
Elem   3  Is Used | SW.Y
Elem   4  Is Used | GL.W
Elem   5  Is Used | FW.A
Elem   6  Is Used | FW.W
Elem   7  Is Used | FW.W^WI.Y
Elem   8  Is Used | SI.Y^SW.Y
Elem   9  Is Used | SI.Y
Elem  10  Is Used | RB.Y
Elem  11  Is Used | GL.W^SE.W
Elem  12  Is Used | WS.W
Elem  13  Is Used | FW.W^LW.Y
Elem  14  Is Used | LO.Y^SC.Y
Elem  15  Is Used | FF.A
Elem  16  Is Used | GL.W^LO.Y

Thanks for looking at this.



Hi Jeff:
How do you get degrib to output this info? Im running it, but I dont see that option. 

I ran with the following command line:

./degrib ds.wwa.bin -C
This produces a file called WWA_10281600.txt (or something similar depending on the date, etc...) 



Hi Jeff:

thanks, i see how to do now.
if you had access to the bytes, would you be able to use them for your purposes?
as a separate issue, i see that we have the wrong local GRIB table for this file. Do you by any chance know where that is?