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789
NOUS41 KWBC 131945 AAA
PNSWSH

Service Change Notice 17-130 Updated
National Weather Service Headquarters Washington DC
345 PM EST Wed Dec 13 2017

To:  Subscribers:
  -NOAA Weather Wire Service
  -Emergency Managers Weather Information Network
  -NOAAPORT
  Other NWS Partners, Users and Employees

From:  David Myrick
  NWS Office of Science and Technology Integration

Subject:  Updated: Changes to North American Mesoscale Model
  (NAM)-based Model Output Statistics (MOS) Guidance,
  effective on or about January 23, 2018

Updated to change the implementation date from Tuesday,
January 30, 2018, to Tuesday, January 23, 2018 and to correct
the location of available parallel data

Effective on or about Tuesday, January 23, 2018, beginning with
the 1200 Coordinated Universal Time (UTC) model run, the
Meteorological Development Laboratory (MDL) will implement
changes to the NAM MOS station-based guidance. These changes
will include new cool- and warm-season equations for the
following elements contained in the short-range NAM MOS text
(MET) and BUFR messages for the 0000 UTC and 1200 UTC cycles:

    Ceiling height
    Opaque sky cover (NAM MOS text products only)
    Visibility
    Obstruction to vision
    6-/12-h probability of precipitation
    6-/12-h categorical precipitation amount

Please note that should the implementation date be declared a
Critical Weather Day (CWD) due to the occurrence or forecast of
significant weather, implementation of these changes will be
delayed until the 1200 UTC model run on the next weekday not
declared a CWD.

These changes are intended to bring the NAM MOS system more in
line with recent operational versions of the underlying model.
Implementation of the new equations will remove any remaining
influence of data collected from the older Eta model on MOS
forecasts for these elements. As such, tests at MDL suggest that
users can anticipate noticeable improvements in forecast skill.
Given that the NAM itself is now frozen, we also anticipate that
this will be the last such set of changes to the operational NAM
MOS system.

In addition to the updated equations, we will be changing the
set of sites for which NAM MOS guidance messages are produced,
due to changes in station reporting habits and data availability
that have occurred since the last revision to the NAM MOS
guidance.  Accordingly, we will unify the set of sites for which
text and BUFR forecast messages are generated in the NAM MOS and
GFS MOS systems. Following implementation of these changes, the
set of sites for which NAM MOS CONUS (MET) and marine (MME)
guidance messages are available will be identical to that
available for the short-range GFS MOS text and BUFR products.
A list of sites affected by these changes may be found at the
following link:

 https://sats.nws.noaa.gov/~mos/mos/nammos_eval/refresh2018/
nammos2018.php

Given that a substantially greater number of stations are being
added to the NAM MOS messages than are being removed, the
overall length of the complete NAM MOS text bulletins and BUFR
messages will increase somewhat.  Users also should be aware
that these changes will result in a slight delay (about 5
minutes) in the dissemination time of NAM MOS products as
compared to present norms.  This delay is due to increased
processing requirements for the revised MOS jobstream and its
migration to a new operational computing platform.  Users should
take the necessary steps for ingest of the expanded station
messages and BUFR files, and to accommodate the later NAM MOS
dissemination times.

As part of NCEPs standard 30-day parallel test, users may find
parallel data for download on NOAA`s Operational Model Archive
and Distribution System (NOMADS) at the following link (files
will reside in nam_mos.YYYYMMDD):

http://para.nomads.ncep.noaa.gov/pub/data/nccf/com/nam/para


Sample NOAPORT/SBN data may be found in real time at:

http://para.nomads.ncep.noaa.gov/pub/data/nccf/noaaport/nam_mos

The following public weather alphanumeric messages and BUFR
products are affected by the above changes:

Table 1.  Communication identifiers for the NAM-based MOS
Public weather text products

    WMO HEADING    AWIPS ID

    FOAK47 KWNO    METAJK
    FOAK48 KWNO    METAFC
    FOAK49 KWNO    METAFG
    FOPA40 KWNO    METPA0
    FOUS44 KWNO    METNE1
    FOUS45 KWNO    METSE1
    FOUS46 KWNO    METNC1
    FOUS47 KWNO    METSC1
    FOUS48 KWNO    METRM1
    FOUS49 KWNO    METWC1
    FQPA40 KWNO    MMEHI1
    FQUS41 KWNO    MMENE1
    FQUS42 KWNO    MMESE1
    FQUS43 KWNO    MMEGL1
    FQUS44 KWNO    MMEGF1
    FQUS45 KWNO    MMENW1
    FQUS46 KWNO    MMESW1
    FQAK47 KWNO    MMEAK1

Table 2.  Communication identifiers for the NAM-based MOS BUFR
messages

    WMO HEADING

    JSML10 KWNO
    JSML11 KWNO
    JSML12 KWNO
    JSML13 KWNO
    JSML14 KWNO
    JSML15 KWNO
    JSML16 KWNO
    JSML17 KWNO

For questions regarding the new NAM MOS guidance and
associated message changes please contact:

 Mark Antolik
 MDL/Silver Spring, Maryland
 301-427-9480
 Mark.Antolik@noaa.gov
or
 Jeffrey Craven
 MDL/Silver Spring, Maryland
 301-427-9475
 Jeffrey.Craven@noaa.gov

For questions related to data flow, please contact:

 Carissa Klemmer
 NCEP Central Operations Dataflow Team
 301-683-0567
 ncep.list.pmb-dataflow@noaa.gov

Links to the MOS products and descriptions are online at:

 http://www.nws.noaa.gov/mdl/synop

NWS National Service Change Notices are online at:

 http://www.weather.gov/os/notif.htm



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