NOUS41 KWBC 131945 AAA


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:


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 NCEPís 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):


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


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††††††††


†††† 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




†††† 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



Jeffrey Craven

MDL/Silver Spring, Maryland



For questions related to data flow, please contact:


Carissa Klemmer

NCEP Central Operations Dataflow Team



Links to the MOS products and descriptions are online at:


NWS National Service Change Notices are online at: