-------- Original Message --------
461
NOUS41 KWBC 241301
PNSWSH
TECHNICAL IMPLEMENTATION NOTICE 09-33
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
855 AM EDT THU SEP 24 2009
TO: SUBSCRIBERS:
-FAMILY OF SERVICES
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS...USERS AND EMPLOYEES
FROM: JASON TUELL
SCIENCE PLANS BRANCH CHIEF
OFFICE OF SCIENCE AND TECHNOLOGY
SUBJECT: NAM/DGEX MODIFICATIONS:
EFFECTIVE NOVEMBER 3 2009
EFFECTIVE NOVEMBER 03 2009...BEGINNING WITH THE 1200
UNIVERSAL COORDINATED TIME /UTC/ MODEL RUN...THE NATIONAL
CENTERS FOR ENVIRONMENTAL PREDICTION /NCEP/ WILL MODIFY THE
NORTH AMERICAN MESOSCALE /NAM/ MODEL. THE CHANGES WILL IMPACT
THE RESULTING NAM AND DOWNSCALED GFS BY NAM EXTENSION /DGEX/
PRODUCTS.
THE FORECAST MODEL AND POST-PROCESSING CHANGES AND THEIR
RESULTING IMPACTS INCLUDE THE FOLLOWING:
-FIX BUG IN HORIZONTAL ADVECTION OF VERTICAL VELOCITY AND
HEIGHT IN NON-HYDROSTATIC MODEL RESULTING IN SLIGHTLY
IMPROVED VERTICAL PROFILES OF VERTICAL VELOCITY ASSOCIATED
WITH FLOWS OVER MOUNTAINS
-MAKE FIX TO RADIATION PHYSICS RESULTING IN CLOUDS BEING LESS
OPAQUE TO SHORTWAVE AND LONGWAVE RADIATION AT GRID POINTS
WHERE RAIN IS FALLING IN THE COLUMN
-CHANGE MICROPHYSICS PARAMETER TO INCREASE THE NUMBER OF
SMALL NON-PRECIPITATING ICE PARTICLES RESULTING IN MORE
REALISTIC NAM GOES LOOKALIKE BRIGHTNESS TEMPERATURES AND
IMPROVED UPPER LEVEL RH BIAS AND ROOT MEAN SQUARE /RMS/
ERRORS VERSUS RAOBS
-CHANGE MICROPHYSICS TO ENFORCE A MINIMUM NUMBER
CONCENTRATION FOR LARGE ICE PARTICLES AT ALL TEMPERATURES
RESULTING IN THE ELIMINATION OF TINY VALUES OF ICE REACHING
THE GROUND WHICH CREATED SPURIOUS ACCUMULATING SNOW IN THE
NAM DURING SPRING/SUMMER
-FIX BUG IN THE ROUTINE THAT DETERMINES CATEGORICAL WEATHER
TYPE RESULTING IN A SLIGHT CHANGE IN THE CATEGORICAL
PRECIPITATION TYPE FOR SOME GRID POINTS
IN ADDITION RADAR ECHO TOP HEIGHT IS BEING ADDED TO ALL NAM
OUTPUT GRIDS CONTAINING SIMULATED RADAR REFLECTIVITY
AVAILABLE ON THE NCEP OR NWS FTP SERVERS. THE RADAR ECHO TOP
HEIGHT WILL NOT BE ADDED TO THE PRODUCTS DISSEMINATED VIA THE
SBN/NOAAPORT WHICH ARE AVAILABLE IN AWIPS.
DATA DELIVERY TIMING WILL NOT BE IMPACTED BY THIS
IMPLEMENTATION. EXPECT A 0.1 TO 0.5 PERCENT INCREASE IN DATA
VOLUME FOR GRIDS TO WHICH RADAR ECHO TOP WILL BE ADDED.
USERS SHOULD 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 PRODUCT DEFINITION SECTION /PDS/ OF THE
GRIB FILES AND ALSO VOLUME CHANGES. THESE ELEMENTS MAY CHANGE
WITH FUTURE NCEP MODEL IMPLEMENTATIONS. NCEP WILL ATTEMPT TO
ALERT USERS TO THESE CHANGES BEFORE IMPLEMENTATION.
FOR MORE DETAILS ABOUT CHANGES TO NCEP/S MESOSCALE MODELS
PLEASE SEE /USE LOWERCASE/
HTTP://WWW.EMC.NCEP.NOAA.GOV/MMB/MMBPLL/ERIC.HTML#TAB4
FOR QUESTIONS REGARDING THESE MODEL CHANGES...PLEASE
CONTACT:
GEOFF DIMEGO
NCEP...MESOSCALE MODELING BRANCH
CAMP SPRINGS MARYLAND
301-763-8000 X 7221
GEOFF.DIMEGO@xxxxxxxx
OR
ERIC ROGERS
NCEP...MESOSCALE MODELING BRANCH
CAMP SPRINGS MARYLAND
301-763-8000 X 7227
ERIC.ROGERS@xxxxxxxx
NWS NATIONAL TECHNICAL IMPLEMENTATION NOTICES ARE ONLINE AT
/USE LOWERCASE/:
HTTP://WWW.NWS.NOAA.GOV/OS/NOTIF.HTM
$$