NOTE: The nws-changes mailing list is no longer active. The list archives are made available for historical reasons.
-------- Original Message --------106 NOUS41 KWBC 061520
PNSWSHTECHNICAL 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/PARANCEP 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@xxxxxxxxTECHNICAL IMPLEMENTATION NOTICES ARE ONLINE AT /USE LOWER CASE/:
HTTP://WWW.WEATHER.GOV/OS/NOTIF.HTM $$
nws-changes archives: