NOUS41 KWBC 311344 AAA



Technical Implementation Notice 14-29, Amended

National Weather Service Headquarters Washington DC

245 PM EDT Thu Jul 31 2014


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Timothy McClung

           Chief, Science Plans Branch

           Office of Science and Technology


Subject:  Amended: Changes to the North American Mesoscale

          (NAM) Analysis and Forecast System: Effective

          August 12, 2014


Amended to add notice that some downscaled guidance products will

be delivered later than in current operations, and mention in

section 3 the change to use the mesonet data reject list from the

RTMA in the NAM/NDAS. 


Effective August 12, 2014, beginning with the 1200 Coordinated

Universal Time (UTC) run, the National Centers for Environmental

Prediction (NCEP) will make the following modifications to the

NAM Analysis and Forecast System:


1) Changes to the NEMS-NMMB forecast model in the NAM Data

Assimilation System (NDAS) and the NAM:


- Replace the legacy GFDL radiation scheme with the NCEP Rapid

Radiation Transfer Scheme (RRTM)

- Extensive modify the gravity wave drag/mountain blocking scheme

by making it more responsive to subgrid-scale terrain

variability, leading to improved large-scale synoptic performance

without degrading 10-m winds

- Add a new version of the Betts-Miller-Janjic (BMJ) convective

parameterization scheme, with moister convective profiles and

less convective triggering, which improves the QPF bias on the

12-km NAM parent domain during the warm season

- Replace the Ferrier microphysics with the new, retuned Ferrier-

Aligo microphysics, with changes targeting improved convective-

storm structures in the NAM 4 km CONUS and 1.33 km fire weather


- Reduce the roughness length for 5 vegetation types, with the

target of improving the 10-m wind bias in the eastern CONUS:

     - Evergreen Needleleaf Forest

     - Deciduous Broadleaf Forest

     - Mixed Forests

     - Croplands

     - Cropland/natural vegetation mosaic


All NMMB model changes will be simultaneously implemented into

the Downscaled GFS by NAM Extension (DGEX) system


2) Changes specific to the NAM nested domains


- Run all nests except the 6 km Alaska domain with explicit

convection instead of reduced convective triggering in the BMJ


- Improve severe storm signatures

  -- Ferrier-Aligo microphysics

  -- Reduce 2nd order diffusion

  -- Separate microphysics species advection for all nests except

the 6 km Alaska nest


3) Analysis/NDAS changes


- Use the hybrid variational ensemble GSI analysis with the NCEP

Global Ensemble Kalman Filter (EnKF)

- Add new satellite bias correction scheme

- Add Variational Quality Control

- Enhance Rawinsonde level

- Use the mesonet wind observation reject list from the NCEP

Real-Time Mesoscale Analysis (RTMA)

- Use GFS ozone analysis in the satellite radiance assimilation

- Add diabatic digital filter initialization (NDAS analyses only)

- Use new observation types:

  -- Replace the use of refractivity with GPS radio occultation

bending angle observations

  -- Add Meteosat-10 winds subtypes with different data thinning

  -- Add GOES-15 radiances

  -- Add new VAD winds with higher vertical resolution and

temporal resolution

- Resume the calculation of the NDAS long-term precipitation

budget adjustment (used to bias-correct the Stage II/IV

precipitation analyses that are used as input to the NDAS

forecast land-surface model) using the NCEP Climatologically-

Calibrated Precipitation Analysis

- Use a modified mesonet data reject list from the Real-Time

Mesoscale Analysis (RTMA) which has most of the stations in NWS

Western Region removed from the list


4) Other changes


- Discontinue the use of the Air Force Weather Agency (AFWA) 23

km snow depth product in lieu of higher resolution snow depth

that will be continuously cycled in the NDAS. Once per day (at

the start of the 0600 UTC NDAS cycle) snow will be removed at any

NAM grid point that is snow-free in the NOAA Interactive Snow and

Ice Mapping System (IMS product); snow will be added at any NDAS

snow-free point that is snow covered in the IMS product.

- For Great Lakes water temperatures, switch from using values

provided by the Great Lakes Environmental Research Laboratory

(GLERL) to using the high-resolution (1/12th degree lat/lon) NCEP

Real-Time Global High Resolution Sea Surface Temperature

(RTG_SST_HR) analysis (the SST analysis used over the rest of the

NAM domain)

- Add the following stations to the 12 km NAM hourly BUFR station



First Column: Numerical Station ID

Second/Third Column: Station Latitude/Longitude

Fourth Column: Station Identifier

Fifth Column: Station Name


000345 42.80N 109.81W KPNA PINEDALE, WY

000346 39.15N 122.15W WLM  WILLIAM, CA

000347 40.88N 121.66W BNY  BURNEY, CA

000348 37.99N 120.38W SON  SONORA, CA

000349 37.74N 118.59W YSV  YOSEMITE VALLEY, CA

000350 36.20N 119.10W LSY  LINDSAY, CA

000351 35.97N 118.54W JHN  JOHNSONDALE, CA

000352 34.83N 118.95W FZP  FRAZIER PARK, CA

000353 36.14N 120.35W COA  COALINGA, CA 

000354 36.65N 118.48W TBM  TABLE MOUNTAIN, CA

000355 42.47N  73.29W KPSF PITTSFIELD, MA

000356 39.21N  82.23W KUNI ATHENS/ALBANY, OH  

000357 40.48N 111.43W K36U HEBER VALLEY MUN APT, UT

000358 33.02N 114.24W B40  YUMA, AZ

000359 31.49N 110.30W B41  FT HUACHUCA, AZ

000360 32.02N 107.87W B42  DEMING, NM

000361 30.43N 104.33W B43  MARFA, TX

000362 28.39N 110.29W B44  EAGLE PASS, TX   

000363 26.57N  98.82W B45  RIO GRANDE CITY, TX  

000364 28.71N  95.96W B46  MATGORDA, TX 

000365 29.81N  91.66W B47  MORGAN CITY, LA  

000366 24.70N  80.51W B48  CUDJOE KEY, FL  

000367 17.98N  67.08W B49  LAJAS, PR  

723066 35.33N  77.97W KGSB SEYMOUR-JOHNSON_AFB, NC 

724397 40.48N  88.92W KBMI BLOOMINGTON/NORMAL, IL 

725490 42.55N  94.20W KFOD FORT DODGE, IA

725635 42.05N 102.80W KAIA ALLIANCE, NE

726710 42.58N 110.11W KBPI BIG PINEY, WY


These stations have been replaced by nearby locations:


Old: 000037 42.00N  95.00W CRL  NR. CARROLL, IA

New: 000037 42.04N  94.79W CRL  CARROLL, IA

Old: 000050 40.90N  92.80W AIA  NR. ALBIA, IA

New: 000050 42.11N  92.92W MAR  MARSHALLTOWN, IA

Old: 000080 40.69N  94.47W RDD  REDDING, IA

New: 000080 41.02N  94.36W CSQ  CRESTON, IA

Old: 724754 37.08N 113.60W KSGU SAINT_GEORGE_(AWOS), UT

New: 724754 37.04N 113.50W KSGU SAINT_GEORGE_(AWOS), UT


5) Changes to the NAM gridded output:


- Added 0-6 km wind shear to these output grids from the NAM 12

km parent (file name on the NCEP ftp server given in quotes):

     -- #212 (40 km Lambert Conformal over the CONUS "awip3d")

     -- #216 (45 km Polar Stereographic over Alaska "awipak")

     -- #218 (12 km Lambert Conformal over the CONUS "awphys")

     -- #242 (11.25 km Polar Stereographic over Alaska "awak3d")

- Added cloud bottom height and 2-m specific humidity to the 12

km Lambert Conformal grid #218 ("awphys")

- Added 0-6 km wind shear to the output grids for all NAM nests

- Added Radar-derived vertically integrated liquid (VIL) to the

NAM 4 km CONUS nest and the NAM 1.33 km fire weather nest

- For all NAM output grids with snow water equivalent: increased

the GRIB precision so that it is output in tenths of kg/m**2

(e.g., 358.3 instead of 358)


Since convective parameterization will be turned off in the

CONUS, Hawaii, Puerto Rico, and Fire Weather nests, the following

fields that are derived from the convective parameterization will

no longer be output from these nested runs:

     - Total convective precipitation

     - Convective precipitation rate

     - Convective cloud efficiency

     - Total convective cloud fraction

     - Total convective cloud top and bottom pressure

     - Deep convective cloud top and bottom pressure

     - Shallow convective cloud top and bottom pressure

     - Derived radar reflectivity from parameterized convection

(was only output previously in the Fire weather nest)


The NAM DNG (smartinit) code was changed by including a

diagnostic wind adjustment scheme to better adjust 10-m winds

over high resolution topography


6) Added the following fields to the 12KM gridded output from the


     - Ventilation Rate

     - Haines Index

     - 1-h Minimum Shelter Relative Humidity

     - Transport Wind

     - PBL Height

     - PBL Height computed from Richardson number


7) Added new DGEX gridded datasets


- Added 6KM NDFD Alaska gridded dataset, files are named:


- Added 5KM NDFD CONUS gridded dataset, files are named:



Based on the most recent timing tests of the NAM change package,

we anticipate the NAM product delivery times to be several

minutes later than the current operational NAM.  Additionally,

during parallel testing it was found that some of the NAM DNG

products will be delivered later than they are today. 

Specifically the 2.5km CONUS products will see a delay – the

initial forecast hours will be comparable in timing, but as the

model iterates the later hours will have increasing delays, with

the final forecast hours being up to 15 to 20 minutes later than

the current delivery timing.  If you have concerns with this

change, please contact Rebecca Cosgrove at 


For more information on this NAM/DGEX upgrade, see


A consistent parallel feed of data will be available on the NCEP

server by late June via the following URLs:


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, 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:


      Geoff DiMego

      NCEP/Mesoscale Modeling Branch

      College Park, MD



      Eric Rogers

      NCEP/Mesoscale Modeling Branch

      College Park, MD 



For questions regarding the dataflow aspects of these datasets,

please contact:


     Justin Cooke

     NCEP/NCO Dataflow Team

     College Park, MD



NWS National Technical Implementation Notices are online at: