[McIDAS #GRW-551250]: RTNEXRAD

Hi Paul,

re:
> I ran the command IMGDISP RTNEXRAD/OHA 2 ID=LOT PLACE=C
> 
> I am getting intermittent response as sometimes the image generates
> and other times it does not. This OHA seems to be the only product with
> this problem.

Hmm... I just tried plotting the OHA product for LOT, and I get the same
result -- a blank image.

re:
> Any idea why it sometimes works and sometimes doesnt?

Yes.  There are a handful of the newer Level 3 products that
are sporadically being sent as very short/abbreviated files.
This situation was seen in Unidata and SSEC testing a number
of months ago, and the hope was that these short products
would be eliminated from the NOAAPort broadcast (and hence
the IDD NEXRAD3 feed).  Since they haven't, code was added
to the NEXRAD server in McIDAS that sets a lower size limit
for the products.  Here is the documentation I put into
the NEXRAD server that comments on the situation:

      /*
      ** <<<<< UPC add 20120514 - hack for bad (too small) Dual Pol images >>>>>
      ** Note:
      **      The test for (cur->size-hedsiz) being less than 600 is arbitrary.
      **      The "real" way to tell if the image is too small is to crack the
      **      image down to the point where its shape is known and then use
      **      that to come up with a heuristic for what is unacceptably
      **      small. I did not do this because it would slow things down
      **      too much.
      **
      **      Typical (cur->size-hedsiz) for small Dual Pol products seen are:
      **      prod type size description
      **      ----+----+----+------------------------------------------------
      **      169  OHA    60 QPE ONE HOUR ACCUMULATION 16 LEVELS
      **      170  DAA    60 QPE ONE HOUR DIGITAL ACCUMULATION ARRAY
      **      174  DOD   550 QPE-PPS ONE HOUR ACCUMULATION DIFFERENCE ID 175
      **      175  DSD   166 QPE-PPS STORM TOTAL ACCUMULATION DIFFERENCE
      */

re:
> I suspect that
> there is a NO PRECIP detected part of the raw file...mcidas does not
> know what to do with it.

Actually, the files are abnormally small; many do not contain any image data
although their header indicates that there should be image data.

re:
> Also, do all the NEXRAD sites generate this product?

Only the sites that are generating dual pol products.  You can see the list
of sites reporting a type of Level 3 product using IMGLIST:

IMGLIST RTNEXRAD/OHA ID=LIST

I just ran this and got a list of 55 stations issuing the OHA product.  This
is in comparison to 151 that are issuing the N0Q product.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: GRW-551250
Department: Support McIDAS
Priority: Normal
Status: Closed