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How do I access past weather?

A good place to look for historical observational data is the National Climatic Data Center at: or

If instead you are interested in historical model data, you could go to the NOMADS Web Interface.

How do I access past NDFD forecasts?

Getting and Viewing Data

Step 1A: Start getting the data

Historic NDFD data is officially being archived at the National Climatic Data Center. To request data do the following:

  1. Go to and select NDFD, or please see the National Centers for Environmental Information.
  2. Enter the start and end dates for the data you need, along with your email address.
  3. Press 'Continue with selections'
  4. Select 'no' for untar files after retrieval if you want the entire US for that range. Select 'yes', if you want specific NDFD files. You will then need to choose amongst the NDFD files which are named using a "bulletinID" and "stationID". Please see the following to locate definitions of the "bulletinID".

  5. After selecting 'no', wait for an email telling you the data is ready. Note If you write down your HAS request number, you can go to If that doesn't work, add "&requestid=000152316" to the URL (replacing 000152316 with your number). to see its progress.

Step 1B: Finish getting the data

After you get your email, or the HAS request is finished:

  1. Go to either:
    •, replacing ######### with your HAS request number.
    •, replacing ######### with your HAS request number.
  2. Save the data to "c:/ndfd/degrib16/data/ncdc" or somewhere that makes sense.
  3. The file comes as a ".tar.Z" file which means it is a compressed (.Z) tape archive (.tar) file. To get the files out you will need to use either: Note: degrib can work with tar files, but not 'compressed' tar files, but it may be easier to work with completely extracted files.

Step 2: Inventory the data (see degrib tutorial: Inventory the data)

  1. Start GUI (tkdegrib)
  2. Click on GIS tab
  3. Enter in c:/ndfd/degrib16/data/ncdc on top (or wherever you put the data)
  4. Double click on the files that you are interested in.

Step 3: See pictures

To do this, we need to pretend that past data is the current NDFD data, so we need to copy the files to the right locations. To do that we have 2 rules:

  1. If the third letter of the filename is a:
    • 'A', it goes in /degrib/data/ndfd/puertori/
    • 'S', it goes in /degrib/data/ndfd/hawaii/
    • 'T', it goes in /degrib/data/ndfd/guam/
    • 'U', it goes in /degrib/data/ndfd/conus/

  2. If the second letter of the filename is a:
    • 'A', it goes in sky.bin
    • 'B', it goes in wdir.bin
    • 'C', it goes in wspd.bin
    • 'D', it goes in pop12.bin
    • 'E', it goes in temp.bin
    • 'F', it goes in td.bin
    • 'G', it goes in maxt.bin
    • 'H', it goes in mint.bin
    • 'I', it goes in qpf.bin
    • 'J', it goes in wx.bin
    • 'K', it goes in waveh.bin
    • 'S', it goes in snow.bin


  • YAAZ99_KWBN_ goes to /degrib/data/ndfd/puertori/sky.bin
  • YGUZ99_KWBN_ goes to /degrib/data/ndfd/conus/maxt.bin
  • YHUZ99_KWBN_ goes to /degrib/data/ndfd/conus/mint.bin

Then if we are on MS-Windows, we can use "tkdegrib" to view the data. (see Tutorial: View the data)

Issues with NCDC site

  • Their file naming convention breaks down since 11/01/2004 00Z -> 200411312351.
  • If they used gzip instead of compress, they could save space in the transfer
  • They appear (from the 11/13/2004 data requested on 11/16/2004) to only have pop12, maxt, mint data for the CONUS, all data except snow for Puerto Rico, all data except qpf for Hawaii, all data except qpf and snow for guam.

Potential improvements to degrib

  • I could add a NCDC Tab to tkdegrib, where the user enters the HAS Job request number, and automatically ftp or https the request to the users machine. The user would have to do Step 1A, but everything after the email could be automated.
  • I could create "c:/ndfd/degrib16/data/ncdc" or "c:/ndfd/degrib16/data/archive" for the user during install, or as part of a NCDC Tab.
  • Might be nice to provide MS-Windows users with a copy of "gunzip" and "tar"
  • Give some info during an inventory to differentiate the sectors
  • tkdegrib cuts off part of the filename so "YDUZ99_KWBN_200409282354" appears to be "YDUZ99_KWBN_20040928"
  • Bug in older versions of tkdegrib when creating images, where no waveh images are needed. (Release fixed version).