>From: Russ Dengel <address@hidden> >Organization: SSEC >Keywords: 200203011521.g21FLFx21046 McIDAS NEXRAD ADDE Russ, re: archived NEXRAD data supported by the McIDAS NEXRAD servers > Thanks. I didn't know what level we were supporting. Level III is composed of products. Level II is the full volume scan data. The NEXR servers support the Level III stuff as that is what is generally available. Availability of Level II data will change as the CRAFT datastream becomes operational in the IDD. re: what do you think about the composite images in NEXRCOMP > The ultimate in cool! Way to go. Glad you like these. Please pass along the dataset info to interested parties in SSEC (like Jerry R. and Rick K.). >How do you generate them???? These are generated using GEMPAK. Chiz wrote a routine that scans directories for new NEXRAD N0R products whose "time" lies within the window that he defines (right now at a half hour). The newest image from each radar that falls within the time window is included in the composite. The 1 km product is written out as a GINI image (my McIDAS distribution includes a GINI server), and the 6 km national, 1 km regional floater, and 10 km RCM images are written out as GRIB messages that I convert to McIDAS AREAs. We are including the 1 km national composite in our 'NIMAGE' IDD datastream. This stream contains all of the NOAAPORT channel 1 and two products (GOES-East and GOES-West NOAAPORT GINI images). It is getting sent to only a small number of Unidata sites because of the data volume and size of files (the VIS sectors are each 26 MB before compression and come out 4 times an hour for both GOES-East and GOES-West). The 1 km N0R composite that gets distributed in PNG compressed form is about 1 MB in size, but that mushrooms to 14 MB after uncompression. Since this product is created about every 8-10 minutes, you can see that you can use up a lot of disk in a hurry. We will be looking into adding support for a compressed version of this product in both GEMPAK and Unidata McIDAS (through my GINI server). Back of the envelop calculations told us that we should be able to get the file size down to about 800 - 900 KB. With this kind of size, it is entirely reasonable to keep a couple of weeks of this product on line at a time. The 6 km national N0R, the 1 km regional N0R, and the 10 km RCM composites are created from GRIB messages by a newly rolled gribdec.tar.Z distribution that I am almost ready to release. In addition to the standalone GRIB to McIDAS GRID converter, gribdec.k, I put together a grib2img.k application that allows one to go directly from GRIB to McIDAS AREA (grib2img.pgm is a fusion of gribdec.pgm and grdimg.pgm). The RCM composites are available in NOAAPORT as GRIB messages and XCD handles these with no problems. The 6 km national and 1 km regional N0R composites are also generated by GEMPAK and output as grib messages that are sent in the FNEXRAD feed of the IDD. I simply wrote an LDM action that converts these grib messages to McIDAS AREAs upon receipt of the GRIBs and then I immediately inject the AREAs that I generate from the gribs into the FNEXRAD feed after compressing them with my AREA image compressor, area2png. These products are reasonably small in the broadcast, around 40 KB or so, and they only expand out to 300 - 400 KB. The reason I include the RCM composite (which is also created by GEMPAK back at the NWS) is so users can compare/contrast the RCM with the MDR product and the Unidata composites. The comparison is startling to say the least! The MDR product is simply horrible and it is misleading. If you use it to look at the echos at the southern tip of Florida today, you would never see that there are cloud streets down there. The RCM product shows the features, but it is so coarse that it is really unusable (and the values are VIP levels). The 6 km national composite shows the features well, but the 1 km product shows them in a spectacular fashion. Again, please tell Jerry and Rick about these images (and the BREF24 enhancement and stretch). Oh, also, I had to modify BAR to be able to work with INFO AUX blocks that contain more than 16 levels; the change was trivial. This mod will also be in my next McIDAS addendum. Later... Tom >From address@hidden Fri Mar 1 14:47:15 2002 >Subject: Re: 20020301: NEXRCOMP composite NEXRAD images Unidata Support wrote: > Glad you like these. Please pass along the dataset info to interested > parties in SSEC (like Jerry R. and Rick K.). I passed the info along to Rick and Jerry. I also sent it to Santek, Achtor and Ackerman. It's always a good idea to show this stuff to Achtor and Ackerman. I think this kind of radar image makes more sense than the individual NEXRAD site files. re: How do you generate them???? I'm sure its a bit more complicated than just pasting the images together. He must be doing some kind of filtering to get rid of ground clutter, "best" value sensing,... It looks really clean. I do see some radar edges along the Gulf coast, but that is to be expected. Russ
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