NOUS41 KWBC 021229



Technical Implementation Notice 11-54

National Weather Service Headquarters Washington DC

830 AM EDT Fri Nov 2 2011


To:†††††† Subscribers

††††††††† -Family of Services

††††††††† -NOAA Weather Wire Service

††††††††† -NOAAPORT

††††††††† -Emergency Managers Weather Information Network

††††††††† Other NWS Partners, Users and Employees


From:†††† Jay Lawrimore††††††

††††††††† Chief, Climate Analysis Branch

††††††††† National Climatic Data Center


SUBJECT:Rounding Algorithm Revision for the Hourly02 and

Daily01 Products Effective December 1, 2012


Effective Tuesday, December 1, 2012, at approximately 1500

Coordinated Universal Time (UTC), The National Climatic Data

Center will change the rounding algorithm used for the hourly02

(CRNH02) and daily01 (CRND01) products. These revisions will

affect some of the reported negative values for stations of the

U.S. Climate Reference Network (USCRN) and the U.S. Historical

Climatology Network-Modernization (USHCN-M).


Prior to September 2012, USCRN used symmetric half-up (away from

zero) rounding for processing and publishing data; however, to

align with the World Meteorological Organizationís requirement to

use asymmetric half-up rounding in important meteorological

summaries and the recommendations of the National Data

Stewardship Team (NDST), USCRN has switched to using asymmetric

half-up rounding for internal data processing. To finalize the

transition to asymmetric half-up rounding, USCRNís data product

software will also switch to using the new rounding algorithm.


Users of the hourly02 or daily01 products should expect to see

some of the previously reported negative values change by 0.1 in

the positive direction (towards zero). This change of rounding

algorithm will not affect the file formats of the two products.

Prior versions of both products will remain available through the

snapshot zip files that are produced weekly.


More details on the rounding practices recommended by the

National Data Stewardship Team can be found at


If you have questions or feedback, please contact:


Scott Embler

National Climatic Data Center

151 Patton Ave

Asheville, NC28803



NWS Technical Implementation Notices are online at: