NOUS41 KWBC 061857 AAB



Service Change Notice 17-105 Updated

National Weather Service Headquarters Silver Spring MD

257 PM EDT Mon Nov 6 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:   Updated: RTMA, URMA and NAM DNG upgrade and Introduction

           of RTMA with Rapid Updates:

           Effective December 12, 2017


Updated to change the scheduled implementation date to 

December 12, 2017


Effective on or about Tuesday, December 12, 2017, beginning with the

1500 Universal Coordinated Time (UTC) cycle, the National Centers for

Environmental Prediction (NCEP) will upgrade the Real-Time Mesoscale

Analysis (RTMA), the Unrestricted Mesoscale Analysis (URMA), North

American Model (NAM) Downscaled Numerical Guidance (DNG) and introduce

the RTMA with Rapid Updates (RTMA-RU).


- Changes to model components

- Addition of new product fields and changes

- Product removals, including NOAAPORT

- Precipitation output changes


1) Changes to Model Components


- The new RTMA-RU is an RTMA analysis run every 15 minutes using the

latest available observational data.  RTMA-RU will run over CONUS

only.  With this upgrade there will also be a change to the products

available from the North American Model (NAM) Downscaled Numerical

Guidance (DNG) system. More specific details of the changes and new

products are provided below.


- A new terrain dataset and land/sea mask will be used in RTMA and

URMA for the continental United States (CONUS), Puerto Rico (PR), and

Hawaii (HI).  The same terrain and land/sea mask will be implemented

in the National Blend of Models during a future upgrade.


- In URMA (but not RTMA), new pseudo-observations of wind, temperature

and moisture will be used over the Great Lakes in an attempt to

simulate over-water conditions over those lakes.  The pseudo-

observations are generated based on water temperature and nearby land-

based observations.  The adjustment formula originated with the Great

Lakes Environmental Research Lab and is also currently used in Great

Lakes nowcasts.


- Hourly precipitation URMA is added to PR and CONUS domains. For

Puerto Rico, coverage is from the Southeast River Forecast Center

(SERFC) hourly Quantitative Precipitation Estimate (QPE).  For CONUS,

hourly gauge-corrected Multi-Radar Multi-Sensor (MRMS) is used to

disaggregate the 6-hourly QPEs from Northwest RFC (NWRFC) and

California-Nevada RFC (CNRFC) into hourlies (no reliable hourly QPEs

from these two RFCs), and combine these with hourly QPEs from the

other 10 CONUS RFCs into a CONUS mosaic.


The filling of the NWRFC/CNRFC is done on the hourly Stage IV CONUS

mosaic, as the precipitation URMA is the Stage IV mapped to the NDFD

grids.  The Stage IV file names remain unchanged, but now the hourly

Stage IV will have NWRFC and CNRFC areas filled with time-

disaggregated data, rather than left as data-free.  In the earlier

runs of the hourly Stage IV/precip URMA, before the corresponding 6h

QPE from these two RFCs become available (as well as on occasion when

there is one or more missing MRMS file in the 6h period), the

CNRFC/NWRFC will still have these areas shown as data-free.  The land-

only data mask is removed from the PR precipitation Stage IV/URMA in

order to provide full PR domain coverage for National Blend of Models



- The built-in coastal steepening of the background error covariance’s

is reduced in RTMA and URMA CONUS, HI, PR and Alaska (AK) domains to

reduce the appearance of zero-increment artifacts around coastlines.


- Additional observations from NOAA’s Cooperative Observer (COOP)

network and the UrbaNet Mesonet will be available for use in URMA (but

not RTMA).


- Associated change to the NAM DNG will be as follows:

a) The NAM DNG is used as input to the RTMA/URMA CONUS, AK, PR, and HI

domains and will be upgraded to be consistent with the same new

land/sea mask and terrain dataset used in RTMA, URMA and RTMA-RU.

b) Decimal scaling (DEC) is changed from 3.0 to 6.0 for increased

precision of specific humidity and to prevent zero values of specific

humidity from being written out. 

c) A bug is corrected in the specific humidity computation (specific

humidity was using surface pressure from NAM Nest rather than the

downscaled surface pressure).  The NAM DNG products can be found on

the NCEP Web Services with a data/nccf/nam/prod/*smart* pattern.



2) Product Changes and Additions


The following changes will apply to products on the NCEP Web Services



Under rtma/prod, urma/prod, nam/prod respectively.


- A new parameter, cloud ceiling height (CEIL), will be added to RTMA

and URMA over Alaska.  Ceiling uses a Rapid Refresh (RAP) based first

guess, and includes observations from METAR sites.  Ceiling is listed

in meters above ground level.

Files under akurma.YYYYMMDD/ like:


Files under akrtma.YYYYMMDD/ like:


Where YYYYMMDD is year, month and day. And HH is cycle from 00-23

(always 2 digits).


 - A new parameter, significant wave height (HTSGW), will be added to

URMA (but not RTMA) over CONUS.  Significant wave height uses

WaveWatch 3 output as a first guess field, and includes observations

from buoys and satellite altimeters.

Files under urma2p5.YYYYYMMDD/ like:





Where YYYYMMDD is year, month and day. And HH is cycle from 00-23

(always 2 digits).


 - A new parameter, minimum and maximum daily relative humidity, will

be added to URMA (not RTMA) over CONUS, Alaska, Hawaii and Puerto

Rico.  Maximum relative humidity will be produced once daily with the

2000 UTC analysis and is valid for the previous 0600-1800 UTC period. 

Minimum relative humidity will be produced once daily with the 0800

UTC analysis and is valid the previous 1800-0600 UTC period.  Note

that no first guess or analysis error files will be available for

minimum and maximum relative humidity, and minimum and maximum

relative humidity will be in a separate file from other variables that

match these names on the NCEP Web Services:








   Where CC=08 for minRH, and CC=20 for maxRH


 - New 2.5 km grids, updating every 15 minutes, referred to as the

Real Time Mesoscale Analysis with Rapid Updates (RTMA-RU).  RTMA-RU

represents a rapidly updating surface analysis system over CONUS that

includes the latest available observed data.  Grids of 2m temperature,

2m dew point, 2m specific humidity, 10m wind speed, 10m wind

direction, 10m wind gust, 10m u-wind component, 10m v-wind component,

surface visibility, cloud ceiling height, and surface pressure will be

made and distributed 20 minutes after analysis time.  RTMA-RU also

leverages the 15 min forecast output from the HRRR for ceiling and

visibility first guess fields and selects the corresponding ceiling

and visibility observations valid closest to analysis time in order to

closely fit these data.


Data will be available on the NCEP Web Services under directory:


With file names like:

  rtma2p5_ru.tHHMMz.2dvaranl_ndfd.grb2 -- analysis field

  rtma2p5_ru.tHHMMz.2dvarges_ndfd.grb2 -- first guess field

Users should note the use of 4-digits (2-digit hour HH and 2-digit

minute MM) used for analysis time in RTMA-RU files. There is no

analysis error file for RTMA-RU and files are available only on the

westward-expanded domain described below. Files should be available

approximately 20 minutes after analysis time.


 - Users should note that the hourly RTMA will run concurrently with

but separately from the RTMA-RU at the top of every hour.  Hourly RTMA

will still be available at the same time and location, and hourly RTMA

output may differ from RTMA-RU output at the top of the hour.


- 200 additional columns have been added to the CONUS output grid over

the Pacific Ocean in a westward expansion of that domain.  Analysis,

first guess, and analysis error files including the westward expansion

will now be available and are named:


Files will still be distributed on their original CONUS grids (NDFD,

NWRFC) along with the new expanded grid.  However users should note

that NCEP plans to discontinue distribution of the smaller, legacy

grids during a future upgrade.


- The new RTMA-RU will be available for download within the grib

filter service under NCEP NOMADS:


- The urma2p5 GRIB2 data on the NCEP Web Services will be reduced from

11 days available to 2 days available to make it more consistent with

the other domains. All RTMA and URMA precipitation data will be

available for 14 days of archive.


3) Product Removals


- The 5km RTMA precipitation will be discontinued on the NCEP Web

Services with this upgrade.


Users should begin using the 2.5km products that are located on the

same web server here:



- Over NOAAPORT/SBN the hourly 5km CONUS RTMA precipitation will be

discontinued. Users should instead be using the 2.5km resolution

output available on NOAAPORT.

  Accumulated Precipitation (APCP) WMO Header removed: LEMA98 KWBR


4) Precipitation Output Changes


The RTMA and URMA precipitation analysis files will be moving to

properly align with the directory structure that follows the RTMA and

URMA. Please see below for those changes.


- The RTMA precipitation GIF images will now be created from the 2.5km

RTMA. The location of the files will move directories:

  pcpanl.YYYYMMDD/pcprtma.YYYYMMDDHH.gif ->



- The Alaska URMA precipitation will change directories and file


 pcpanl.YYYYMMDD/pcpurma_ak.YYYYMMDDHH.06h ->



-  The Puerto Rico precipitation will change directories and file


  pcpanl.YYYYMMDD/pcpurma_pr.2017091006.06h -> 



- New 1 hourly URMA precipitation analysis files will be available in

their parent domain directories:






More information about the RTMA, URMA and RTMA-RU is available at:


A consistent parallel feed of data is available on the NCEP server via

the following URLs:



CONUS hourly RTMA data will be under sub-directory rtma2p5.YYYYMMDD

15-minute RTMA-RU data will be under sub-directory rtma2p5_ru.YYYYMMDD





Stage IV:


Parallel (RTMA/URMA) Precip Analysis data will be under its various

parent domain directories as noted above.


NCEP urges all users to ensure their decoders can handle changes in

content order and volume changes. These elements may change with

future NCEP model implementations. NCEP will make every attempt to

alert users to these changes before implementation.


Questions, comments or requests regarding this change should be

directed to the contacts below.  We will review feedback and decide

whether to proceed.


For questions regarding science changes, please contact:


   Vijay Tallapragada

   NCEP/EMC Modeling and Data Assimilation Branch

   College Park, Maryland



For questions regarding the data flow aspects of these data sets,

please contact:


   Carissa Klemmer

   NCEP/NCO Dataflow Team Lead

   College Park, Maryland



NWS National Service Change Notices are online at: