NOUS41 KWBC 061210 AAA
Service Change Notice 17-105 Updated
National Weather Service Headquarters Silver Spring MD
1210 AM EDT Fri Oct 6 2017
-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 November 14, 2017
Updated to include more details about the changes to the URMA
precipitation output and change the implementation date to
November 14, 2017
Effective on or about Tuesday, November 14, 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
- 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
A note on precipitation URMA and Stage IV: NCEP Stage IV
is a 4.6km precipitation analysis based on the QPEs produced by
the River Forecast Centers. Alaska and Puerto Rico Stage IV are
from the QPEs produced by APRFC and SERFC for the AK and PR
regions, respectively; CONUS Stage IV is a mosaic of QPEs from
the 12 CONUS RFCs, with the exception of hourly Stage IV over
CNRFC/NWRFC as described above (using MRMS to do time-
disaggregation, not simply input from RFCs).
- The built-in coastal steepening of the background error
covariances is reduced in RTMA and URMA CONUS, HI, PR and AK
domains to reduce the appearance of zero-increment artifacts
- Additional observations from the NOAA 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
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
2) Product Changes and Additions
The following changes will apply to products on the NCEP Web
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:
- The Alaska URMA precipitation will change directories and file
- The Puerto Rico precipitation will change directories and
- 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 will be available on the NCEP
server beginning Sept 14 via the following URLs:
RTMA and RTMA-RU:
CONUS hourly RTMA data will be under sub-directory
15-minute RTMA-RU data will be under sub-directory
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:
NCEP/EMC Modeling and Data Assimilation Branch
College Park, Maryland
For questions regarding the data flow aspects of these data
sets, please contact:
NCEP/NCO Dataflow Team Lead
College Park, Maryland
NWS National Service Change Notices are online at: