NOUS41 KWBC 201235



Public Information Statement PNS17-40

National Weather Service Headquarters Silver Spring MD

835 AM EST Wed Dec 20 2017


To:        Subscribers:

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners and NWS Employees


From:      Brian Gross, Acting Director

           NCEP/Environmental Modeling Center


Subject:   Soliciting Comments on the Proposed Upgrade 

           of the RAP and HRRR operational models through

           January 20, 2018


The Environmental Modeling Center (EMC) and Earth Systems

Research Laboratory (ESRL) are proposing to upgrade the Rapid

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

models in late spring of 2018. The NWS is seeking comments on

this proposed change through January 20, 2018.


On November 20, 2017, EMC began disseminating experimental RAPv4

and HRRRv3 guidance to users. This change was announced in an

evaluation letter distributed on November 20, 2017.  The

official evaluation page is online at:


The RAP will be extended to 39 hours for the 03/09/15/21Z model

cycles to support forecast extensions of the HRRR out to 

36 hours at the 00/06/12/18Z model cycles. This upgrade also

includes the addition of a HRRR-Alaska system, which runs every

3 hours out to 18 hours and every 6 hours out to 36 hours. The

full list of changes are described in presentations accessible

from the official evaluation page. Expected benefits from this

upgrade include more optimal precipitation and reflectivity

biases, especially in the first few hours of the HRRR, more

retention of low-level clouds, overall improvement of synoptic

fields, and better depiction of turbulence and winds over



Current location of RAP output on para nomads:


Current location of HRRR output on para nomads:



The NWS will evaluate all comments to determine whether to

proceed with this upgrade.


Send comments on this proposal by January 20, 2018 to:


Geoff Manikin, EMC


Ben Blake, EMC,


National Public Information Statements are online at: