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20010306: ncdc radar at stc (cont.)

>From: alan anderson <address@hidden>
>Organization: St. Cloud State
>Keywords: 200102202133.f1KLXZL10511 McIDAS NEXRAD display

Alan,

>Yes, after I went home last night, I thought about how little we knew
>concerning
>the nature of these files.  The student is the one who has been communicating 
>with NCDC, and all he is aware of is that these are supposed to be some 
>samples of the Level III Nexrad data, in which he can look at Storm Total 
>Precip.  We need to talk some more with the person at NCDC.

The digital precipitation array is a NEXRAD Level III product.  It is
just one that I never added support for in McIDAS.  Given the nature of
this file, I would have to write a routine that would extract the
information and store it in a McIDAS GRID file.  This may not be too
hard, but it is something that I have never tried to do.

>From you comments above, I take it we need to get  Image files.

There are three different image products that deal with storm precipitation:
1-hour precip. totals; 3-hour precip. totals; and storm total precip.

The storm total precip. product is one that you may have seen on the
evening weather.  I know that I have seen this product, especially for
NEXRADs that are observing hurricanes.

>Reading the contents of DSSERVE.BAT  and also the section on your web site
>titled
>Configuring NIDS, NOWrad and GINI ADDE Servers, it appears there at least 2
>kinds
>of image products for Radar;  NOAAPORT Nexrad and WSI NIDS.  
>Is there an advantage to one or the other?  

Yes!  The NOAAPORT ones are free :-).  The NEXRAD Level III products
that are being sent in NOAAPORT contain the exact same information as
the products one can purchase from WSI (and other NIDS vendors).  The
difference is that the NOAAPORT products have been zlib compressed;
have a different header; and do not include the radar ID at the end of
the file (it is in the header).  The "data" portion of the images are
identical (after uncompressing the zlib-compressed bit) since they all
originate from the PUP.

Also, the names assigned to the products by WSI (and the other NIDS
vendors) is different from the names used by the NWS for the NOAAPORT
images:

WSI       NWS       Product
---------+---------+--------------------------------------
BREF1     N0R       Base Reflectivity at Tilt 1
BREF2     N1R       Base Reflectivity at Tilt 2
BREF3     N2R       Base Reflectivity at Tilt 3
 ...
TOPS      NET       Echo Tops
VIL       NVL       Vertically Integrated Liquid water
 ...
PRE1      NP1       1-hour Precip Totals
PRE3      NP3       3-hour Precip Totals
PRET      NPT       Storm Total Precip.
 ...

The reason I kept the information about setting up datasets for WSI
NIDS products in my McIDAS documentation is for sites that opted to
continue to receive the NIDS products from WSI (perhaps they are simply
waiting until their contracts expire?).  In the next release, I may
remove the WSI setup information from that web page altogether (push it
to an inconspicuous link).

Also because of the transition period, I had to add support for both
WSI and NOAAPORT products in DSSERVE.BAT.  This will also change in the
7.8 release as it is confusing to newbies.

>I will try and make sure we are getting the right files.  Sorry for our not
>knowing what we dealing with.  

No problem.  My question to you is whether or not you have a good
feeling for how to go about setting up an ADDE dataset now?  In
particular, do you see why I had to modify the NCDCNEXR.CFG file that
you created?

Another thing that I did not touch on in our previous emails was the
difference between the NEXRAD station ID and the ID for the issuing
station.  In the example files that we tried to get working, the ID
KMPX could well have been for the issuing station and not for the
NEXRAD itself.  In fact, the issuing station is KMPX and the NEXRAD ID
is MPX (NEXRAD IDs are all 3 characters long right now; this may change
in the future).  If the products you have had been Storm Total Precip.
images, and if you had tried to list/load/copy them using ID=KMPX in
the McIDAS IMGLIST/IMGIDSP/IMGCOPY routines, you would have gotten a
failure since the ID contained in the file is MPX and MPX != KMPX.

At this point you may be asking yourself why I am going on about this.
If/when you get to requesting the realtime NEXRAD data through the IDD
(and you should; setting this up won't take much time), you will find
that you can request images from either the issuing station (e.g.,
KMPX) or from the NEXRAD ID itself (e.g., MPX).  If there was a
one-to-one correspondence between the issuing station and the NEXRAD,
then there would be no problem.  The problem is that there are some
stations that issue NEXRAD products for more than one radar!

Please let me know if your student actually needs the information from the
digital precipitation array products.  If this is crutial, then I will
look into how much work it would take to read the files and create output
grids in McIDAS format.

Tom