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NOUS41 KWBC 071953

Technical Implementation Notice 15-32 Amended
National Weather Service Headquarters Washington DC
320 PM EDT Tue Jul 7 2015

To:       Subscribers:
          -Family of Services
          -NOAA Weather Wire Service
          -Emergency Managers Weather Information Network
          Other NWS partners and NWS employees

From:     Timothy McClung
          Chief Operating Officer
          NWS Office of Science and Technology Integration

Subject:  Amended: Upgrade the Short Range Ensemble Forecast
          System Effective July 28, 2015

Amended to:

-Change the implementation date from August 4 to July 28, 2015
-Mention downstream change to the genesis tracker file
-Include reference to TIN 15-30 on BUFR station table changes

Effective on or about Tuesday, July 28, 2015, at 1500
Coordinated Universal Time (UTC), the National Centers for
Environmental Prediction will upgrade the Short Range Ensemble
Forecast System (SREF).

The SREF model upgrades include the following:

- The 7 Weather Research and Forecast (WRF) Nonhydrostatic
Mesoscale Model (NMM) members will be eliminated.  This
includes the following members: ctl, n1, p1, n2, p2, n3, p3.

- The Nonhydrostatic Multiscale Model on B-Grid (NMMB) model
members will be increased from 7 to 13 members.  The new NMMB
members will be: n4, p4, n5, p5, n6, p6.

- The Advanced Research WRF (WRF-ARW) members will also be
increased from 7 to 13 members.  The new ARW members will be:
n4, p4, n5, p5, n6, p6.

- Each ensemble member ID will be encoded in the GRIB data for
the 26 individual raw SREF members.

- Cloud ceiling height will change from Above Ground Level
(AGL) to Above Sea Level (ASL) as requested by the aviation
user community.

- Science changes include more diversity in model initial
conditions (IC), IC perturbations and physics.  The vertical
resolution of the model will increase from 35 to 40 vertical

- As a uniform measure across all NCEP regional models (see
BUFR Station change TIN 15-30, NOUS41 KWBC 091327, PNSWSH,
30bufr_staids.htm), 138 new stations have been added in the
bufr/sounding output. See the above mentioned TIN for the
detail changes.

- All SREF-based downstream jobs such as cyclone track will
not be impacted in their formats and file names, but are
calculated based on new 26 members instead of 21 members,
where new members are n4, n5, n6, p4, p5 and p6

Graphical data is viewable here:

The Environmental Modeling Center (EMC) Mesoscale Modeling
Branch (MMB) has a publicly available website which can
provide users more information concerning the SREF modeling
system as well as other NCEP regional modeling systems:

AWIPS product changes:

The total number of ensemble members in this upgrade will
increase from 21 to 26 due to the discontinuation of the NMM
members, and the increase of both the NMMB and ARW members
from 7 to 13 members.  The increase in ensemble membership
will be reflected in the following AWIPS products:

- For 2-meter Temperature and 3-hourly Precipitation products
on Grid #221 (32 km North American Lambert Conformal Grid),
the GRIB2 Product Definition Template (PDT) will be modified
to identify the individual ensemble members.

- For the Mean, Probability, and Spread products on Grids #212
(40 km Contiguous United States (CONUS) Lambert Conformal
Grid), #216 (45km Alaska Polar Stereographic Grid), and #243
(Eastern North Pacific Grid), the GRIB2 encoding will reflect
the total increase in ensemble members from 21 to 26.

File name changes:

There will be no changes in the file naming convention for the
NMMB files, where the model core in file names is represented
with the string nmb.  However, the file naming convention
for all ARW files will be modified by replacing the previous
em string with the arw string.

Also, the file naming convention for the mean, probability and
spread cluster files on the NCEP FTP server and NOMADS will
change to lead with sref and the model cycle:

[mean|prob|spread].sref.cluster[1-6].fHH.grib2 ->

where CC is the model cycle (03, 09, 15, 21), HH is the 2-
digit forecast hour (00, 03, 06, ..., 81, 84, 87)

Data delivery timing/volume/content changes:

With this upgrade, no changes in delivery time are expected.
The GRIB2 product definition section (PDS) will be modified to
identify the individual SREF members.  In combination with the
model ID (111=NMMB and 116=ARW), users will be able to
identify each of the unique SREF members, as follows: ctl, p1
(+1), n1 (-1), p2 (+2), n2 (-2), ..., p6 (+6), n6 (-6).  Due
to the increase in SREF members from 21 to 26 and the addition
of the member ID to each members GRIB2 file, users can expect
approximately a 10% increase in the data volume for each of
the raw individual ensemble members files.

Output from the SREF is available for North America, the
Contiguous United States, Alaska, and Eastern Pacific domains

NOMADS data is available via the following URL:

Output from the SREF is available for the CONUS domain on the
NWS FTP server at the following location:

where CC is the cycle (03, 09, 15, 21) and YYYYMMDD is the
current date.

A consistent parallel feed of data will be made available on
the NCEP HTTP server at the following URL:

NCEP encourages all users to ensure their decoders are
flexible and are able to adequately handle changes in content
order, changes in the scaling factor component within the
product definition section (PDS) of the GRIB files, and also
any volume changes which may occur. These elements may change
with future NCEP model implementations. NCEP will make every
attempt to alert users to these changes prior to any

For questions regarding the scientific content of the modeling
system, please contact:

     Geoff DiMego
     College Park, Maryland 20740
     Phone: 301-683-3764
     Jun Du
     College Park, Maryland 20740
     Phone: 301-763-3704

For questions regarding the dataflow aspects of these data
sets, please contact:

     Kelly Kempisty
     NCEP/NCO Dataflow Team
     College Park, Maryland 20740
     Phone:  301-683-0567

This and other NWS technical implementation notices are
available online at:

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