NOUS41 KWBC 051155 AAB
Technical Implementation Notice 15-33 Amended
National Weather Service Headquarters Washington DC
756 AM EDT Mon Oct 5 2015
To:       Subscribers:
          -Family of Services
          -NOAA Weather Wire Service
          -Emergency Managers Weather Information Network
          Other NWS Partners, Users and Employees
From:     Tim McClung
          Chief Operating Officer
          NWS Office of Science and Technology Integration
Subject:  Amended: Changes to North American Mesoscale Model

(NAM)-based Model Output Statistics (MOS) Guidance

Effective on a date to be determined


Amended to change the implementation date from Tuesday,

October 6, 2015, until a date to be determined.

Updates to the NAM-based MOS guidance by the NWS Meteorological 
Development Laboratory (MDL), originally scheduled for Tuesday, 
October 6, 2015, have been postponed due to requirements for 
additional evaluation from potential users and coordination 
with NCEP.  An amended TIN will be published once a new 
implementation date is set. When implemented, the updates will 
include new equations for forecasts of snowfall amount for 
6- and 12-h thunderstorm probability, and for 6- and 12-h
probability of severe weather. Implementation of the new equations 
will remove any remaining influence of data collected from the older 
eta-coordinate model on MOS forecasts for these elements. In addition, 
MDL will introduce new NAM MOS probabilistic and categorical guidance 
for cool-season precipitation type.


Before the implementation date, 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):

The addition of precipitation type will increase the length of the 
cool-season NAM MOS messages by three lines in the body of text for 
each station contained in the MOS alphanumeric (MET) bulletins, and 
by three records for each station in the BUFR messages.  These added 
lines will contain probabilistic forecasts for the occurrence of 
freezing precipitation and snow (labeled POZ, POS), as well as a 
categorical forecast of the most likely precipitation type (labeled TYP). 
Due to changes in reporting frequencies, sufficient data were not 
available for development of new precipitation type equations at 14 sites 
currently contained in the NAM MOS system. Therefore, precipitation type 
guidance will not be produced and no additional information will appear 
in the MET and BUFR messages for these sites. These sites are listed in 
Table 1 below.  
NAM MOS messages for Alaskan sites also will contain an additional 
two lines for the new 6- and 12-h thunderstorm probability forecasts 
(labeled T06 and T12) during the convective season, May 1 through 
September 30; however, since the observed frequency of severe convective 
weather events over Alaska is quite low, it was not possible to obtain 
stable statistical relationships for the severe weather probabilities 
at those sites. Therefore, all Alaska severe weather probability 
forecasts will be coded as missing (99) at their respective positions 
within the NAM MOS messages.
Users should take the necessary steps for ingest of this additional 
information.  Following implementation of these changes, the format 
of the cool-season NAM MOS messages will be identical to those 
being generated for the companion short-range GFS MOS text (MAV) 
and BUFR products.  
Table 1:  Sites for which NAM MOS precipitation type guidance will 
not be available
     ID        STATION                       LAT      LON
     K3A6      NEWHALL                CA     34.37N   118.57W 
     K47A      CHEROKEE CNTY ARPT     GA     34.31N    84.42W 
     K48I      SUTTON/BRAXTON CO AP   WV     38.69N    80.65W 
     K4BL      BLANDING               UT     37.62N   109.47W 
     K4HV      HANKSVILLE             UT     38.37N   110.72W 
     KHMS      HANFORD                WA     46.57N   119.60W 
     KNHZ      BRUNSWICK NAS          ME     43.89N    69.94W 
     KPFN      PANAMA CITY            FL     30.20N    85.80W
     KRZZ      ROANOKE_RAPIDS         NC     36.44N    77.71W 
     KTDO      TOLEDO                 WA     46.48N   122.80W 
     PADT      SLANA AIRPORT          AK     62.70N   143.98W 
     PALV      BIG RIVER LAKE         AK     60.82N   152.30W 
     PASP      SHEEP MOUNTAIN         AK     61.82N   147.51W 
     PAWR      WHITTIER               AK     60.77N   148.68W
The following public weather alphanumeric messages and BUFR 
products are affected by the above changes: 
Table 2:  Communication identifiers for the NAM-based MOS 
Public weather text products
     WMO HEADING    AWIPS ID       
     FOAK47 KWNO    METAJK         
     FOAK49 KWNO    METAFG         
     FOPA40 KWNO    METPA0         
     FOUS44 KWNO    METNE1         
     FOUS45 KWNO    METSE1         
     FOUS46 KWNO    METNC1         
     FOUS47 KWNO    METSC1         
     FOUS48 KWNO    METRM1         
     FOUS49 KWNO    METWC1         
Table 3: Communication identifiers for the NAM-based MOS BUFR 
     JSML10 KWNO
     JSML11 KWNO
     JSML12 KWNO
     JSML13 KWNO
     JSML14 KWNO
     JSML15 KWNO
     JSML16 KWNO
     JSML17 KWNO 
For questions regarding the updates to the NAM MOS guidance and
associated message changes please contact:
  Mark Antolik
  MDL/Silver Spring, Maryland
  Matthew Peroutka 
  MDL/Silver Spring, Maryland 
Links to the MOS products and descriptions are online at:
NWS National Technical Implementation Notices are online at: