NOUS41 KWBC 161308 AAA



Public Information Notice: Amended

National Weather Service Headquarters Washington DC

908 AM EDT Tue Jul 16 2013


To:       Subscribers:

          - Family of Services

          - NOAA Weather Wire Service

          - Emergency Managers Weather Information Network

          - NOAAPORT

          Other NWS partners and NWS employees


From:     Andrew Stern

          Acting Chief, Meteorological Services Division


Subject:  Amended: Extending Comment Period on Increasing the

          Resolution in the National Digital Forecast Database

          Until December 31, 2013


Amended to extend the comment period to December 31, 2013


On August 28, 2012, the spatial resolution in the National

Digital Forecast Database (NDFD) was increased, on an

experimental basis, to 2.5km resolution for all forecast times.

In addition, the temporal resolution was made accessible at one

hour resolution for the first 36 hours from NDFD issuance time in

experimental status. These are the finest spatial and temporal

resolutions at which NWS Weather Forecast Offices (WFOs) in the

conterminous United States (CONUS) provide forecasts.  Forecasts

from WFOs and NWS National Centers that employ coarser

resolutions are mapped onto the finer resolution NDFD grid.


The increased spatial and temporal resolution applied to files

containing data for the entire CONUS, but not Alaska, Hawaii,

Guam, Puerto Rico, the Virgin Islands, or the 16 CONUS

subsectors. These subsectors remain at their current operational



The NWS will accept comments and feedback on the increase in

resolution during the experimental period through December 31,

2013.  Links to surveys are online at:


Pending analysis of comments, the NWS will decide whether or not

to proceed to transition the experimental fine resolution to

operational status for the CONUS.  Current operational

resolutions would continue for Alaska, Hawaii, Guam, Puerto Rico,

the Virgin Islands, and the 16 CONUS subsectors.


Specifications for operational and experimental NDFD grids can be

viewed at the following URL:


The NDFD continues in parallel in operational phase at current

spatial and temporal resolutions throughout the experimental

period. Experimental fine resolution forecasts are updated

approximately 15 minutes after operational NDFD forecasts. NDFD

graphics and Simple Object Access Protocol/REST/XML services are

provided from operational NDFD grids.


To access experimental fine resolution grids use the following




Experimental grids for forecast days 1 through 3 are provided in

individual files for each day in order to limit file sizes. 

Experimental grids for selected elements are more tightly packed

in GRIB format with both decimal and binary scaling applied.  

GRIB encoding characteristics for each NDFD element can be viewed

at the following URL:


File structures and GRIB packing for operational NDFD files are

unchanged during the experimental period.  Experimental Ice

Accumulation and daily Maximum and Minimum Relative Humidity

grids also remain unchanged.


WMO headers and file structures for current operational and

experimental NDFD files can be viewed at:


WMO headers and files structure for the new experimental fine

resolution files can be viewed at:


General information on accessing and using NDFD elements is

online at:


For general questions regarding NDFD data, please email:


For technical questions regarding NDFD data, please contact:


  David Ruth

  Chief, Mesoscale Prediction Branch

  NOAA/NWS Office of Science and Technology

  1325 East West Highway

  Silver Spring, Maryland 20910


For questions regarding this notice, please contact:


  Andy Horvitz

  National Weather Service

  Office of Climate Water and Weather Services

  1325 East West Highway

  Silver Spring, Maryland 20910


Service Change Notices specifically related to NDFD are online



National Public Information Notices are online at: