RE: DIFAX Scripts

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For those really interested, the TIF files are on the NWS web site and you can 
cross reference this to the FTP files.

The FTP files have a WMO header like name convention.  For example (all with 
.TIF extensions), here are some common ones:

QAUA00 - radar summaries (24/day)
QYAA00 - surface analyses (8/day)
QGUA00 - weather depictions (8/day)
QTTA00 - max temp
QTTA01 - min temp
QETA00 - 24 hr precip
QSTA00 - snow cover

* most of these are twice a day
PGBE99 - 12, 24 hr sig wx, sfc prog
QHUQ00 - 36, 48 hr sfc prog and description
QHUA17 - 200 mb analysis
QHUA25 - 250 mb analysis
QHUA15, QMUA15 - 300 mb analysis (diff chart for 0 and 12)
QHTA11 - 500 mb analysis
QHTA07 - 700 mb analysis
QHUA04 - 850 mb analysis
QTTR00 - NGM MOS POP forecast
QTTE00 - NGM max/min forecast

* once a day
PGUE00 - day 1,2 convective outlook
QTMI01 - day 3-4 pop anom, day 3 temp anom
QTMI00 - day 4-5 temp anom
QPUT88 - 6-10 day prog

* Multipanel that need to be put together, twice a day
QHUA89,88 - LI, prec water, frz lvl, mn RH 4 panel
QHUA71,70 - NGM 0 hr 4 panel
QHUE71,70 - NGM 12 hr 4 panel
QHUI71,70 - NGM 24 hr 4 panel
QHUM71,70 - NGM 36 hr 4 panel
QHUQ71,70 - NGM 48 hr 4 panel
QHUM86,85 - NGM 850 48 hr 4 panel

I take these charts and use ImageMagick's convert and montage to put them 
together and then output PNG.  I also rotate them 180 degrees for viewing on a 
screen with something like xv.

For download, I wrote FTP code in Perl to do the hard work.  It downloads the 
directory listing, decodes the dates to determine which chart has changed since 
the last check.  Then I download the chart and do the post processing.

I won't give away all my secrets but for those who want to do the legwork, 
everything you need is there!

BTW, that NWS page covers about 90% of all current Difax charts.  NWs has told 
me that this will continue to be there and that they are updating the hardware 
on this system.  They will give priority use to some customers such as 
commercial data providers and maybe one or two Unidata sites (check with the 
NWS contact listed on bottom of web page).  So it may be a good idea for one or 
two universities to handle most of the load and distribute it through IDD.  
When they upgrade and provide priority service, Unidata won't be bundled into 
the low priority group.

Good luck!
Daniel Vietor               Mail: devo@xxxxxxxxxxxxx
Unisys Corp                 Title: Engineer/Meteorologist
221 Gale Lane               Phone: 610-925-5206
Kennett Square PA 19348     Fax: 610-925-5215

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