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19990804: GEMPAK/METAR question

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  • Subject: 19990804: GEMPAK/METAR question
  • Date: Wed, 4 Aug 1999 10:57:01 -0600
Scot,

To view METAR data within Gempak, it must first be
decoded into a Gempak surface file.

Gempak requires prior conversion of the data from METAR into 
a Gempak surface file since:

1) There is no station location information in a Metar observation.
   METARs only contain a station ID, but no lat lon info. You have to
   look up that information in a separate table- which takes time.
   Gempak places all that info in the Gempak file once. If you
   want "on-the-fly" displays, then you will be spending alot of
   time looking for station locations.

2) Storing data into a decoded format is more efficient since you
   only have to decode the data once. Retrieval from the data base
   is much faster. On-the-fly decoding would be much slower.

The GEMPAK surface file is binary. I know that WXP uses an ASCII formatted
decoded file to use with its plot programs, it still must be decoded into
that format- but remains ASCII readable. WXP is available from Unisys.

Steve Chiswell
Unidata User Support



On Wed, 4 Aug 1999, Scot Loehrer wrote:

> Steve,
> 
> A quick question from across the hall...
> 
> For one of our field programs I have made available
> files containing regular ASCII METAR formatted surface
> observations (each file contains the data for one
> site over the duration of the project).  
> 
> I have received a request for a software package that 
> can generate displays of these data without any prior 
> manipulation of the data files.
> 
> Can one use GEMPAK to directly use these files to 
> generate displays of the data?
> 
> If not, can GEMPAK utilize ASCII METAR formatted data
> set up in some other file structure (i.e. files by
> day or hour)?
> 
> Or, does the ASCII METAR formatted data have to be 
> converted to some other format prior to the data being
> usable by GEMPAK?
> 
> Do you happen to know of any software packages that 
> utilize ASCII METAR formatted data directly to develop
> displays?
> 
> Thanks for any help.
> 
> Scot Loehrer
> UCAR/JOSS
>