20020305: hosting ADDE access to Unidata NEXRAD composite imagery (cont.)

>From: Eirh-Yu Hsie <address@hidden>
>Organization: Aeronomy Laboratory/NOAA/DOC
>Keywords: 200203041624.g24GOMK11535 McIDAS ADDE NEXRAD composite

Hsie,

re: cirrus is not running LDM 5.1.4

>I am running LDM 5.1.3 on cirrus.  I do not understand why it does not
>take FNEXRAD.

I believe that the FNEXRAD alias for NMC3 was added in 5.1.4.

>I upgrade the LDM server on cirrus to 5.1.4 and change the
>ldmd.conf to:
>
>request         FNEXRAD
>        "^pnga2area Q5"
>        thelma.ucar.edu

OK.  If the LDM started ('ldmamdin start' did not hang) then all should be
well.

>I alreay compiled it.  But never switch to it.

OK, I saw the directory there, but the failure to recognize FNEXRAD alerted
me to it not being used on cirrus.

>What is the difference between FNEXRAD feed and NEXRAD feed?

They are totally different feeds.  FNEXRAD contains NEXRAD Level III
products for three radars.  The three that are included are selected on
an ongoing basis by the floater selector site which is currently
Millersville University with the College of DuPage acting as a backup.
In addition to the NEXRAD Level III products, we are injecting composite
imagery into FNEXRAD from motherlode:

o 1 km N0R floater composite both as a grib message and as an image in
  PNG compressed AREA format
o 6 km N0R national compoiste both as a grib message and as an image in
  PNG compressed AREA format
o 10 km RCM national composite as an image in PNG compressed AREA format

The grib message that the RCM image is created from is on NOAAPORT in
the NWS TG (channel 3).

>Beacuse I already have a NEXRAD feed:
>
>request NEXRAD
>        ".*"
>        sirocco.srcc.lsu.edu

NEXRAD (also known as NNEXRAD) is a feed of all of the products for all
NEXRAD stations in the country.

>What does the filter "^pnga2area Q5" do?

This pattern limits requests to FNEXRAD products whose headers begin with
'pnga2area Q5'.  These are the composite products listed above.

You could also get the grib messages in the FNEXRAD feed.  These have
headers that match patterns like:

radar_mosaic_regional_(.*) !(.*)!

 and

radar_mosaic_national_(.*) !(.*)!

These grib messages are created by a GEMPAK routine that Chiz wrote.

I put an action in motherlode's pqact.conf file to kick off conversion
of these grib messages to McIDAS AREA image files which I then compress
with the ldm-mcidas routine area2png and inject back into the FNEXRAD
feed using pqinsert.  The end result of all of this is image versions
of the grib messages being sent in FNEXRAD very soon after the original
grib messages.  The compressend images are decoded/uncompressed on the
user side using the ldm-mcidas routine pnga2area.

Have you taken a look at the composites?  I just took a look at the 1
km national N0R composite now being hosted on stratus, and it looks
good (not much weather across the US, mind you).  I also verified that
all of the composites are flowing to your site and are correctly being
scoured.

Tom