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Weather Forecast Data

The National Weather Service publishes a tremendous amount of information at http://www.nws.noaa.gov/. What you may not know is that they also make data available via ftp. There's an experimental project that you might enjoy.

Available Data

See http://www.nws.noaa.gov/ndfd/technical.htm for a listing of what you can get, and http://www.nws.noaa.gov/ndfd/technical.htm for the file names and ftp directories to access. For example, to get temperature forecasts for my area (Massachusetts), I'd get ftp://tgftp.nws.noaa.gov/SL.us008001/ST.expr/DF.gr2/DC.ndfd/AR.neast/ds.temp.bin

That's a packed binary file, and you need the "degrib" program to decode them. Get that from http://www.nws.noaa.gov/mdl/NDFD_GRIB2Decoder/. There are instructions on the web site for compiling a Linux version, but I found that all I needed to do after untarring the download was:

cd ./degrib/src/degrib
cp makefile.linux makefile
cp degrib /usr/bin

The degrib program is simple to use, but you first need a file containing the latitude and longitude for the point (or points) you are interested in. I used this:


which represents two points very near my home, one somewhere in Providence RI, and one at the far western part of Mass. You can look up coordinates at http://www.bcca.org/misc/qiblih/latlong.html; if the longitude is expressed as West, you want to multiply it by -1 for your file. Now to run degrib:

# looking at max temperature file here
degrib ds.maxt.bin -P  -pntFile lat -pntStyle 0

That produces this output:

element, unit, refTime, validTime, (42.060000,-71.110000), (42.070000,-71.100000), (41.480000,-71.200000), (42.250000,-73.200000)
MaxT, [F], 200401122100, 200401140000, 38.191, 38.191, 38.191, 29.191
MaxT, [F], 200401122100, 200401150000, 8.452, 8.452, 12.232, 6.292
MaxT, [F], 200401122100, 200401160000, 12.341, 12.341, 16.301, 4.241
MaxT, [F], 200401122100, 200401170000, 9.281, 9.281, 12.341, 5.321
MaxT, [F], 200401122100, 200401180000, 22.177, 22.177, 23.257, 21.277
MaxT, [F], 200401122100, 200401190000, 25.273, 25.273, 28.333, 24.373
MaxT, [F], 200401122100, 200401200000, 30.299, 30.299, 31.199, 28.319

That's forecasted temperatures for the 14th through the 20th; I ran this on Jan 12,2004.

Different output formats are available. If you get something like this:

element, unit, refTime, validTime, (42.060000,71.110000), (42.070000,71.100000), (41.480000,71.200000), (42.250000,73.200000)
MaxT, [F], 200401122100, 200401140000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401150000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401160000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401170000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401180000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401190000, 9999.000, 9999.000, 9999.000, 9999.000
MaxT, [F], 200401122100, 200401200000, 9999.000, 9999.000, 9999.000, 9999.000

it means that you either downloaded the wrong file (the point isn't included in the file you downloaded) or you misentered the points (did you forget to use a minus sign for longitude?).

Have fun. There's lots of other data available; current and historical. Finding it can sometimes be challenging, but just about anything you could ever want to know about weather is there somewhere.

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© Tony Lawrence

FTP data isn't just in the directory I mentioned above. As I said, it can be hard to figure out where to look. These



are of some help.


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