-------- Original Message --------
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NOUS41 KWBC 061520
PNSWSH
TECHNICAL IMPLEMENTATION NOTICE 08-79...AMENDED
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
1020 AM EST THU NOV 6 2008
TO: SUBSCRIBERS:
-FAMILY OF SERVICES
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS...USERS AND EMPLOYEES
FROM: JASON TUELL
CHIEF...SCIENCE PLANS BRANCH
OFFICE OF SCIENCE AND TECHNOLOGY
SUBJECT: AMENDED: NORTH AMERICAN MESOSCALE MODEL CHANGES
EFFECTIVE: DECEMBER 16 2008
REFER TO: TECHNICAL IMPLEMENTATION NOTICE /TIN/ 08-79 TRANSMITTED
ON OCTOBER 9 2008
AMENDED TO POSTPONE THE EFFECTIVE DATE FROM DECEMBER 2 2008 TO
DECEMBER 16 2008 DUE TO ISSUES RAISED DURING THE EVALUATION
PERIOD. THE ORIGINAL NOTICE WITH THE REVISED DATE IS BELOW:
EFFECTIVE TUESDAY DECEMBER 16 2008...BEGINNING WITH THE 1200
COORDINATED UNIVERSAL TIME /UTC/ RUN...SEVERAL CHANGES WILL BE
MADE TO THE FOLLOWING:
- WEATHER RESEARCH FORECAST NON-HYDROSTATIC MESOSCALE MODEL
/WRF-NMM/ RUNNING IN THE NORTH AMERICAN MESOSCALE MODEL /NAM/
- NAM DATA ASSIMILATION SYSTEM /NDAS/
- DOWNSCALED GLOBAL FORECAST SYSTEM /GFS/ WITH ETA EXTENSION
/DGEX/
- GRIDPOINT STATISTICAL INTERPOLATION /GSI/ ANALYSIS WHICH
PROVIDES INITIAL CONDITIONS TO THE NDAS AND NAM FORECASTS.
THESE CHANGES ARE BEING MADE TO IMPROVE MODEL PERFORMANCE.
THE MODEL MODIFICATIONS INCLUDE:
1. A CHANGE TO THE WRF-NMM RADIATION PARAMETERIZATION BY DOUBLING
THE ABSORPTION COEFFICIENT FOR CLOUD WATER AND CLOUD ICE.
2. TWO COLD-SEASON RELATED CHANGES TO THE WRF-NMM LAND-SURFACE
PHYSICS...CHANGING THE COMPUTATION OF POTENTIAL EVAPORATION TO
DECREASE LINEARLY WITH BULK RICHARDSON NUMBER UNDER STABLE
CONDITIONS /WEIGHTED BY SNOW COVERAGE/ AND ALLOWING THE SLOPE OF
THE SATURATED HUMIDITY FUNCTION WITH RESPECT TO TEMPERATURE TO
DECREASE LINEARLY WITH SNOW COVERAGE.
3. CHANGING THE TURBULENT MIXING AND DIFFUSION SCHEMES SO THAT
THEY VERTICALLY MIX AND DIFFUSE EACH HYDROMETEOR SPECIES
SEPARATELY.
THE ANALYSIS CHANGES INCLUDE:
1. ASSIMILATION OF NEW OBSERVATION TYPES...INCLUDING METOP2
RADIANCE DATA...AND TAMDAR/AMDAR AIRCRAFT DATA
2. USE OF THE LATEST /1Q 2008/ VERSION OF THE GSI ANALYSIS...AND
AN IMPROVED VERSION OF THE COMMUNITY RADIATIVE TRANSFER MODEL
/CRTM/
THE CHANGES TO THE NDAS INCLUDE:
1. EACH NDAS CYCLE WILL BE INITIALIZED USING ATMOSPHERIC STATES
FROM THE GLOBAL DATA ASSIMILATION SYSTEM /GDAS/ INSTEAD OF THAT
FROM THE PREVIOUS NDAS CYCLE /SO-CALLED PARTIAL CYCLING
OPTION/...NDAS LAND-SURFACE STATES WILL CONTINUE TO BE FULLY
CYCLED FROM THE PREVIOUS NDAS RUN.
2. THE OBSOLETE WRF STANDARD INITIALIZATION /WRF-SI/ SOFTWARE
USED TO PROCESS THE GDAS FIRST GUESS FOR THE NDAS IS BEING
REPLACED WITH THE NEW WRF PREPROCESSING SYSTEM /WPS/ SOFTWARE.
3. REPLACE THE CURRENT AFWA SNOW DEPTH ANALYSIS WITH A NEW HIGHER
RESOLUTION /23-KM/ AFWA ANALYSIS.
ALL WRF-NMM MODEL CHANGES WILL BE SIMULTANEOUSLY IMPLEMENTED INTO
THE DGEX...AS WILL THE REPLACEMENT OF WRF-SI SOFTWARE WITH WPS
SOFTWARE...WHICH PROCESSES THE 78-H NAM FORECAST INTO INITIAL
CONDITIONS TO THE DGEX.
NAM OUTPUT CHANGES INCLUDE:
1. A NEW ENLARGED 32-KM OUTPUT GRID WHICH COVERS THE ENTIRE
EXPANDED NAM COMPUTATIONAL DOMAIN...WHICH WILL HAVE THE SAME
FIELDS AS THE EXISTING 32-KM GRID #221 /AWIP32/ FILE.
2. ADD RICHARDSON NUMBER BASED PLANETARY BOUNDARY LAYER
HEIGHT...MIXED LAYER DEPTH...AND TRANSPORT WIND COMPONENTS TO
GRID #221 /AWIP32...32 KM NORTH AMERICA/...GRID #218/AWIP12...12
KM CONUS/...AND GRID #242/AWP242...11.25 KM ALASKA/ STATIONS.
3. CHANGE THE NAM POST-PROCESSOR SOFTWARE TO USE SHELTER
TEMPERATURE INSTEAD OF SKIN TEMPERATURE IN THE UNDERGROUND CHECK
FOR LOWEST FREEZING LEVEL HEIGHT.
4. ADD SNOW MIXING RATIO ON PRESSURE LEVELS TO THREE OUTPUT
GRIDS /GRID #104..GRID #212...GRID #237/ THAT CURRENTLY ONLY
OUTPUT CLOUD ICE...SO THAT TOTAL ICE CAN BE COMPUTED.
THE COMBINED IMPACT OF THESE CHANGES LEADS TO:
1. IMPROVED NAM FORECAST PERFORMANCE BASED ON QUANTITATIVE SKILL
SCORES FOR HEIGHTS AND TEMPERATURE /RMS ERROR AND BIAS/ OVER BOTH
THE CONUS AND ALASKA.
2. NEUTRAL OR BETTER QUANTITATIVE PRECIPITATION FORECAST SCORES
/DEPENDING ON SEASON/ WITH LOWER PRECIPITATION BIAS.
3. SLIGHT IMPROVEMENTS TO MOST NEAR-SURFACE FORECASTS...
ESPECIALLY IN THE COLD SEASON /DUE TO THE WRF-NMM MODEL RADIATION
CHANGE/.
MORE DETAILS ABOUT THESE CHANGES CAN BE SEEN AT /USE LOWERCASE
LETTERS/:
HTTP://WWW.EMC.NCEP.NOAA.GOV/MMB/MMBPLL/PARALOG/PARALOG.
NAMX_OPSPLL_FALL2008.HTML
WHEN IT BECOMES AVAILABLE...A COPY OF THE BRIEFING PACKAGE FOR
THE NCEP DIRECTOR CAN BE FOUND AT /USE LOWERCASE LETTERS/:
HTTP://WWW.EMC.NCEP.NOAA.GOV/MMB/NAMCHANGES_FALL2008/
NAM_UPGRADES.FALL2008.HTML
DATA DELIVERY TIMING WILL NOT BE IMPACTED BY THIS IMPLEMENTATION.
THE NAM DELIVERY TIME WILL NOT CHANGE.
DATA VOLUMES ARE EXPECTED TO CHANGE FOR SOME NAM OUTPUT GRIDS DUE
TO THE CHANGES OUTLINED ABOVE. FOR THOSE GRIDS IMPACTED...THESE
CONTENT CHANGES WILL IMPACT ALL DISSEMINATION ROUTES WHICH
INCLUDE NOAAPORT...THE NWS PUBLIC FTP SERVER AND THE NCEP PUBLIC
FTP SERVER.
PARALLEL DATA FOR THE NAM...NDAS AND DGEX WILL BECOME AVAILABLE
ON THE NCEP FTP SERVER ON OCTOBER 14 2008. IT WILL BE AVAILABLE
AT THE LINKS BELOW /USE LOWERCASE LETTERS/:
FTP://FTP.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/NAM/PARA
NCEP ENCOURAGES ALL USERS TO ENSURE THEIR DECODERS ARE FLEXIBLE
AND ARE ABLE TO ADEQUATELY HANDLE CHANGES IN CONTENT ORDER...
PARAMETER FIELDS CHANGING ORDER...CHANGES IN THE SCALING FACTOR
COMPONENT WITHIN THE PDS OF THE GRIB FILES AND ALSO ANY VOLUME
CHANGES WHICH MAY BE FORTHCOMING. THESE ELEMENTS MAY CHANGE WITH
FUTURE NCEP MODEL IMPLEMENTATIONS. NCEP WILL MAKE EVERY ATTEMPT
TO ALERT USERS TO THESE CHANGES BEFORE IMPLEMENTATION.
FOR QUESTIONS CONCERNING THESE CHANGES...PLEASE CONTACT:
GEOFF DIMEGO
NCEP...MESOSCALE MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301.763.8000 X7221
EMAIL: GEOFF.DIMEGO@xxxxxxxx
OR
ERIC ROGERS
NCEP...MESOSCALE MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301.763.8000 X7227
EMAIL: ERIC.ROGERS@xxxxxxxx
TECHNICAL IMPLEMENTATION NOTICES ARE ONLINE AT /USE LOWER CASE/:
HTTP://WWW.WEATHER.GOV/OS/NOTIF.HTM
$$