NOUS41 KWBC 231319 AAA



Technical Implementation Notice 16-27 Amended

National Weather Service Headquarters Washington DC

919 AM EDT Tue Aug 23 2016


To:      Subscribers:

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS Partners and Employees


From:    Timothy McClung

         Portfolio Manager

         Office of Science and Technology Integration


Subject: Amended: RTMA, URMA, NAM DNG and SREF Upgrade: Effective

         August 23, 2016


Amended to include wording about slight degradation to the RTMA

gust product.


Effective on or about Tuesday, August 23, 2016, beginning with

the 1200 Universal Coordinated Time (UTC) cycle (15Z cycle for

the SREF), the National Centers for Environmental Prediction

(NCEP) will upgrade the Real-Time Mesoscale Analysis (RTMA), Un-

Restricted Mesoscale Analysis (URMA), and North American Model

(NAM) Downscaled Numerical Guidance (DNG) and make minor product

modifications to the Short-Range Ensemble Forecast (SREF) System. 

The changes include some scientific changes and product changes. 

They are outlined below for each modeling system.




- There is evidence of a slightly degraded RTMA/URMA gust product

for CONUS due to the guess field from the HRRR having stronger

gust speeds, owing to a change in how the PBL height is computed

in the model. This finding is based on 35-day RTMA/URMA

statistics for the partial months of July and August of 2016.


- Replace the current terrain and land/sea mask used in the

system with the new EMC/GFE consensus terrain and land/sea mask

in the 2.5km CONUS domain. The use of the common terrain and

land/sea mask will eliminate the need for NWS forecasters to

reduce the RTMA and URMA analyses to their local GFE terrain.


- Improve the CONUS and Alaska grids of wind speed by analyzing

wind speed directly as a scalar, as opposed to deriving it from

the control variables of stream function and velocity potential.


- Produce new URMA output for Hawaii and Puerto Rico on 2.5km

grids.  These new URMA systems will provide "truth analyses" for

the National Blend of Models Project.  The output will contain

analysis and analysis uncertainty for the following parameters:

Surface pressure, 2m-temperature, 2m-dewpoint, 2m-specific

Humidity, 10-m u-wind component, 10m-v wind component, 10-m wind

speed, 10-m wind direction, 10-m gust, and surface visibility. 

At this time these products will only be available on the NCEP

ftp server at: and


in subdirectories hiurma.YYYYMMDD and prurma.YYYYMMDD.  The

filenames will be:





where 2dvarges is background/first guess, 2dvaranl is analysis

and 2dvarerr is analysis uncertainty, YYYYMMDD is year, month,

day and CC is cycle from 00-23.


- Add GRIB2 files for Cloud Ceiling Height (CEIL) analysis (anl)

and Cloud Ceiling Height analysis uncertainty (err) for RTMA and

URMA for the 2.5km CONUS grids only.  At this time these products

will only be available on the NCEP ftp server at: and


The filenames will be:





where 2dvaranl is analysis and 2dvarerr is analysis uncertainty,

CC is cycle from 00-23, and ndfd and nwrfc denote which CONUS

grid is used.


GRIB2 files for CEIL should be considered experimental at this

time.  After sufficient evaluation, if these fields are promoted

to operational, we will put these fields into the larger

RTMA/URMA output files and no longer have them in separate files.


- Add URMA-CONUS grids of maximum temperature (TMAX) and minimum

temperature (TMIN) to NDGD at:


    file name - ds.maxt.bin  MAX temperature

    file name -  MIN temperature


and to NOAAPORT with the following WMO headers:


     LTQA98 KWBR         URMA TMAX or TMIN Analysis

     LTQA98 KWBR         URMA TMAX or TMIN Analysis Uncertainty


Please note that the MAX temperature grid is only available from

the 08Z cycle run, and the MIN temperature from the 20Z cycle



NAM DNG Changes


- Replace the current terrain and land/sea mask used in the

system with the new EMC/GFE consensus terrain and land/sea mask

for the 2.5km CONUS domain. 


- Modify the wind gust calculation at intermediate hours

(1,2,4,5, etc) to use the maximum of the NAM nest wind gust and

downscaled wind speed.  This calculation is already done at the

0,3,6, etc forecast hours and this change will make it consistent

across all forecast hours.


- Add new variables Cloud Ceiling height [gpm], and Mean Sea

Level Pressure (Eta model reduction) [Pa] to the 2.5km CONUS, 3km

Alaska, Puerto Rico and Hawaii NAM DNG files on the NCEP ftp



- Add hourly output of Total Cloud Cover field for all NAM DNG

domains.  It was previously available only every 3 hours.

- Remove the 5km CONUS and 6km AK NAM DNG GRIB files from the

NCEP servers. These products have been replaced by the 2.5km

CONUS and 3km Alaska products.


Removed:     nam.YYYYMMDD/nam.tCCz.smartconusFF.tm00.grib2


Replacement: nam.YYYYMMDD/nam.tCCz.smartconus2p5FF.tm00.grib2



Where CC is cycle and FF is forecast hour


- Modify the GRIB encoding for the Haines Index fields will be

modified to use the value 9.9 x 10^10 for the missing value.


SREF Changes

- Update the SREF ensemble mean, probability and spread products

on NOAAPORT to add the 0-3h accumulated precipitation parameter,

which is erroneously being skipped.


- Add the following fields to all of the SREF output grids (grids

132, 212, 216, 221 and 243) on the NCEP ftp server at:


Water Equivalent of Snow Depth (both instantaneous and 3-hourly

Snow Depth.


- Increase the forecast hours available in the probability files

available on the NCEP ftp server for grid 132 from 72 hours to

87.  The filename is sref.tCCz.pgrb132.prob_3hrly.grib2


Real-time sample parallel data for the RTMA/URMA and NAM is

available via the following URLs:


More information about the RTMA and URMA update is available at:


Parallel RTMA:


Parallel URMA:


Operational RTMA:


Operational URMA:


Parallel vs. Ops RTMA:


Parallel vs. Ops URMA:


For questions regarding these changes, please contact:


    Geoff DiMego

    NCEP/EMC Mesoscale Modeling Branch

    College Park, Maryland



For questions regarding the data flow aspects of these data

sets, please contact:


    Carissa Klemmer

    NCEP/NCO Dataflow Team

    College Park, Maryland



NWS National Technical Implementation Notices are online at: