NOUS41 KWBC 241755 AAE



Service Change Notice 17-105 Updated

National Weather Service Headquarters Silver Spring MD

155 PM EST Wed Jan 24 2018


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 February 7, 2018


Updated to reflect that the NAM DNG changes outlined below will

be made operational on February 7, 2018


Due to a configuration issue the NAM DNG changes were not made

on December 13 with the RTMA and URMA upgrade cycle. This update

will only impact the NAM DNG advertised changes to both output

products and downstream applications.     


Effective on or about Wednesday, December 13, 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



- 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


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 at:


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



 - 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





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



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 names:

  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



A consistent parallel feed of data will be available on the NCEP

server beginning Sept 14 via the following URLs:




CONUS hourly RTMA data will be under sub-directory


15-minute RTMA-RU data will be under sub-directory







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: