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-------- Original Message --------
765
NOUS41 KWBC 021912
PNSWSH
Technical Implementation Notice 11-54, Amended
National Weather Service Headquarters Washington DC
210 PM EST Fri Mar 3 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):
Effective March 20, 2012
Amended to set the implementation date for March 20, 2012
On or about March 20, 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
Camp Springs , Maryland
301-763-8000 X7734
manuel.pondeca@xxxxxxxx
For questions regarding the dataflow aspects of these datasets,
please contact:
Rebecca Cosgrove
NCEP/NCO Dataflow Team
Camp Springs , Maryland 20746
301-763-8000 X 7198
ncep.pmb.dataflow@xxxxxxxx
NWS National Technical Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
$$
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