NOUS41 KWBC 101145



Service Change Notice 17-86

National Weather Service Headquarters Silver Spring MD

910 AM EDT Mon Jul 10 2017


To:        Subscribers:

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Dave Myrick

           NWS Office of Science and Technology Integration


Subject:   Sea Surface Temperature change to the RAP and HRRR

           Effective July 12, 2017


Effective on or about July 12, 2017, beginning with the 0100

Coordinated Universal Time (UTC) run, the National Centers for

Environmental Prediction (NCEP) will make a change to the Sea

Surface Temperature (SST) analysis within the Rapid Refresh

(RAP) and the High Resolution Rapid Refresh (HRRR) models


Currently, the RAP and HRRR combine two SST analyses, the 

Real-Time Global (RTG) and a Two-Dimensional Variational 

(2D-Var), in making their respective daily 01 UTC SST updates.

The temperatures of resolved rivers and small inland lakes are

present in both SST analyses, but only the 2D-Var analysis is

used to determine the small lake and river temperatures

ultimately initialized in the RAP and HRRR.


It has recently come to the attention of NCEP that small inland

lake temperatures are much too cold in the RAP and HRRR as a

result of poor 2D-Var analyses. NCEP is proposing to discard the

2D-Var analysis and rely solely on the RTG analysis for

determining all initial water temperatures in the RAP and HRRR

(except for a few larger inland lake temperatures which are and

will continue to be specified by climatology). As a result of

discarding the 2D-Var analysis, users can expect resolved river

and small inland lake temperatures to be significantly improved

in the RAP and HRRR and in all downstream models. The largest

downstream impacts will occur within the Real-Time Mesoscale

Analysis (RTMA) and Unrestricted RTMA (URMA). For the full list

of downstream models, please email the contacts below.


These changes will impact all model output on NCEP web services

and NOAAPORT/SBN. Users do not need to take any action and will

continue to receive the data as they are currently.


Any questions, comments or requests regarding this change should

be directed to the contacts below.  We will review any feedback

and decide whether to proceed.


For questions regarding these model changes, please contact:


  Geoff Manikin

  NCEP/Environmental Modeling Center

  College Park, Maryland



For questions regarding the dataflow aspects of these data sets,

please contact:


  Carissa Klemmer

  NCEP/NCO Dataflow Team Lead

  College Park, Maryland



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