NOUS41 KWBC 141534


Technical Implementation Notice 11-10, Amended

National Weather Service Headquarters Washington DC

1100 AM EST Dec 14 2011


To:       Subscribers:

          -Family of Services

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Timothy McClung

          Chief, Science Plans Branch

          Office of Science and Technology


Subject:  Amended: Change to Wave Model Products:

          Effective Date December 20, 2011


Amended to reschedule this implementation for December 20, 2011.  Also, please note the following added to the last amendment of this TIN:  Due to the large file size of the multi_1.txxz.spec_tar file currently being disseminated via the NCEP server, NCEP will begin making this spectral output file available in compressed format with the filename multi_1.txxz.spec_tar.gz.  In a future implementation in 2012, the non-compressed file will be removed from the NCEP server, so we encourage users to begin transitioning to the compressed version now.

Effective on Tuesday, December 20, 2011, beginning with the 1200 Coordinated Universal Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will modify the spectral output grid products from the Multi-grid Global Wave Model. 

This model is run using WAVEWATCH-III v3.14. Recent upgrades of the model to v3.14 increased the spectral resolution of the model from a 25x24 spectral domain (frequency and direction) to a 50x36 domain. For backward compatibility, however, the spectral output from the model was kept at 25x24.  This upgrade will change the spectral output to match the internal model domain.

The key changes are as follows:

1. The frequency spectrum will now start from 0.035

  (instead of 0.0412)

2. The logarithmic increment will now be 1.07 (as opposed to

   1.1). i.e., the next frequency will be 7% higher as opposed

   to 10% higher earlier.

3. There will be 50 frequency components as opposed to the

   earlier 25 frequency components (with the highest resolved

   frequency being 0.963 as opposed to 0.406 earlier)

4. There will be 36 directional components as opposed to the

   24 directional components earlier. This means that the

   directional resolution will now be 10 degrees as opposed to

   15 degrees earlier  

The spectral output files from these models are disseminated via the NCEP server at



The following files will be affected:


where xx is the model cycle.

This change will not affect the non-spectral output files from these models.  The spectral products that are changing are not available on NOAAPORT or in AWIPS.

Sample output files reflecting this spectral resolution change are available at:

Details about the NCEP Multi-grid Wave Model are online at:

For questions regarding these model changes, please contact:  

  Hendrik Tolman

  NCEP/Marine Modeling and Analysis Branch

  Camp Springs, Maryland

  301-763-8000 ext 7253


For questions regarding the dataflow aspects of these data sets, please contact:


  Rebecca Cosgrove

  NCEP/NCO Dataflow Team

  Camp Springs, Maryland 20746

  301-763-8000 x 7198


NWS National Technical Implementation Notices are online at: