NOUS41 KWBC 231430 AAA
PNSWSH
Technical Implementation Notice 11-54,
Amended
National Weather Service Headquarters
930 AM EDT Mon Jan 23 2012
To: Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information
Network
-NOAAPORT
Other NWS Partners, Users and
Employees
From: Tim McClung
Chief, Science Plans Branch
Office of Science and
Technology
Subject: Amended: Change to First Guess
Used by Real-Time
Mesoscale Analysis To Rapid Refresh (RAP): Postponed
until late February/early March 2012
In late February/early March 2012, with the
1200 Coordinated
Universal Time (UTC) run,
the Real-Time Mesoscale Analysis
(RTMA) for CONUS at both 5-km and 2.5-km
resolution will use the Rapid Refresh
(RAP) instead of the Rapid Update Cycle (RUC) as the forecast model that provides the first
guess. The current
5- and 2.5-km resolution RTMA terrain
fields, which were created at ESRL/GSD, will also be replaced by terrain fields
created at NCEP/EMC.
The RTMA is a set of gridded surface and
near-surface analyses that are created by combining observations with the first
guess, weighted by their error statistics.
The change of the first guess is necessary
since the RUC is being replaced by the RAP on that same date (see NWS Technical Implementation Notice 11-53 for details of the RUC to RAP transition). The main impact of this change will occur in
areas of sparse observational data where the RTMA analysis relies more heavily
on the guess field than in areas with greater observational coverage. While the use of the new RTMA terrain will
have little impact on the overall analysis on scales larger than a few grid
lengths, users who might be using the RTMA terrain to locally adjust the
analysis are advised of the need to use the updated terrain provided in the
output files.
NCEP urges all users to ensure their
decoders can handle changes in content order, changes in the scaling factor
component within the product definition section (PDS) of the GRIB files,
changes to the GRIB Bit Map Section (BMS), 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.
For questions regarding these changes,
please contact:
Manuel Pondeca
NCEP/Mesoscale Modeling Branch
301-763-8000 X7734
For questions regarding the dataflow
aspects of these datasets, please contact:
Rebecca Cosgrove
NCEP/NCO Dataflow Team
301-763-8000 X 7198
NWS National Technical Implementation
Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
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