NOUS41 KWBC 031756



Technical Implementation Notice 11-22

National Weather Service Headquarters Washington DC

155 PM EDT Fri Jun 3 2011


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Tim McClung

           Chief, Science Plans Branch

           Office of Science and Technology


Subject:   Global Ensemble CCPA Changes:

           Effective August 23, 2011


On or about Tuesday, August 23, 2011, beginning with the 1200 Coordinated Universal Time (UTC) run, the Climatologically Calibrated Precipitation Analysis (CCPA) product will be updated to include 3-hourly accumulations. 


CCPA 3-hourly accumulated precipitation analyses are generated by splitting each 6-hourly accumulated precipitation analysis based on a ratio calculated from hourly Stage II (over the Northwest River Forecast Center) or Stage IV (over other continental U.S. River Forecast Centers) values at each HRAP grid cell. The analysis is then interpolated from the HRAP grid to other grids.  The 3-hourly CCPA covers the same domain as the
6-hourly analysis and is available on the same 5 output grids:


1. HRAP Grid (same as the Stage IV grid)

2. National Digital Forecast Database (NDFD) CONUS grid

3. 0.125 degree CONUS latitude/longitude grid (Grid ID 110)

4. 0.5 degree latitude/longitude grid with data coverage over

   CONUS only

5. 1.0 degree latitude/longitude grid with data coverage over

   CONUS only (Grid ID 3)


For specifications of Grid IDs 3 and 110, see


The 6-hourly CCPA data is currently disseminated via the NCEP server and is available at:



where YYYYMMDD is the date and XX is the model cycle.  In addition to the currently existing 6-hourly files, on August 23rd there will be 2 new files for each grid, corresponding to the two 3-hourly sub-periods.


Data delivery timing will be slightly impacted by this implementation as additional time will be needed to compute the 3-hourly analyses.


Test data will be available at:


More information regarding the CCPA and its scientific implementation can be found at:


Disclaimer:  NCEP would encourage all users to ensure their decoders are flexible and are able to adequately handle changes in content order, parameter fields changing order, changes in the scaling factor component within the Product Definition Section (PDS) of the GRIB files and also any volume changes which may be forthcoming.  These elements may change with future NCEP model implementations.  NCEP will make every attempt to alert users to these changes prior to any implementation.



For questions regarding these changes, please contact:


    Dingchen Hou

    NCEP/EMC Global Modeling Branch

    Camp Springs , Maryland

    Phone: 301-763-8000 x7015


NWS National Technical Implementation Notices are online at: