NOUS41 KWBC

PNSWSH

TECHNICAL IMPLEMENTATION NOTICE 05-68\...AMENDED

NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC

XXXX XM EDT XXX MAR XX 2006

TO: FAMILY OF SERVICES /FOS/ SUBSCRIBERS\...NOAA WEATHER WIRE SERVICE
/NWWS/ SUBSCRIBERS\... EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
/EMWIN/ SUBSCRIBERS\...OTHER NATIONAL WEATHER SERVICE /NWS/ CUSTOMERS
AND PARTNERS\...NWS EMPLOYEES

FROM: PAUL HIRSCHBERG

CHIEF\...SCIENCE PLANS BRANCH

OFFICE OF SCIENCE AND TECHNOLOGY /OST/

SUBJECT: UPDATED: REPLACEMENT OF NCEP ETA MODEL WITH THE NON-HYDROSTATIC
MESOSCALE MODEL POSTPONED TO JUNE 13 2006

REFER TO: TECHNICAL IMPLEMENTATION NOTICE /TIN/ 05-68 TRANSMITTED ON
OCTOBER 3 2005

AMENDED TO DELAY THE EFFECTIVE DATE FOR THE REPLACEMENT OF THE NCEP ETA
MODEL WITH THE NON-HYDROSTATIC MESOSCALE MODEL FROM MARCH 28 2006 UNTIL
JUNE 13 2006.

THE ORIGINAL NOTICE\...WITH EXPANDED INFORMATION AND REVISED DATES\...IS
GIVEN BELOW:

ON THE ABOVE EFFECTIVE DATE\...BEGINNING WITH THE 1200 COORDINATED
UNIVERSAL TIME /UTC/ RUN\...THE NATIONAL CENTERS FOR ENVIRONMENTAL
PREDICTION /NCEP/ WILL REPLACE THE FORECAST MODEL CURRENTLY RUN IN THE
NORTH AMERICAN MESOSCALE SYSTEM. THE 12 KM HORIZONTAL RESOLUTION ETA
MODEL IS CURRENTLY USED IN THIS SYSTEM. IT WILL BE REPLACED WITH A 12 KM
HORIZONTAL RESOLUTION WEATHER RESEARCH AND FORECASTING /WRF/ VERSION OF
THE NON-HYDROSTATIC MESOSCALE MODEL /NMM/ MODEL.

THE DIFFERENCES BETWEEN THE NCEP ETA AND WRF NMM SYSTEMS ARE AS FOLLOWS:

1\) Model Changes\
\
- Replace Eta prediction model with WRF version of the Non-hydrostatic
Meso Model (WRF-NMM)\
- Extended model top pressure from 25 mb to 2 mb\
- Replace Eta step-mountain vertical coordinate with NMM hybrid
sigma-pressure vertical coordinate\
- Refined/retuned numerous aspects of the Eta model physics for use in
the NMM\
\
2) Analysis Changes\
\
- Replace Eta 3DVAR analysis system with the new unified GSI analysis
system that has been adapted for application to the WRF-NMM\
- Replace NEXRAD Level II.5 data in Eta 3DVAR with NEXRAD Level II
radial wind data in GSI\
- GSI uses background errors based on WRF-NMM forecasts; Eta 3DVAR used
background errors based on GFS forecasts\
- Use of dynamically retuned observational errors\
\
3) Data Assimilation Changes\
\
- Implement direct use of observed precipitation analysis values in the
Land-surface physics modules -- this replaces prior use of nudging /to
precipitation and GOES cloud top pressures/

THERE WILL BE NO NAME CHANGES ASSOCIATED WITH THIS MODEL REPLACEMENT.
PRODUCTS AVAILABLE ON NOAAPORT WILL ALSO REMAIN UNALTERED WITH THIS
CHANGE. ALL CURRENT NAM GUIDANCE PRODUCTS WILL CONTINUE TO BE AVAILABLE
AT THE SAME TIME IN THEIR CURRENT RESOLUTIONS AFTER THIS CHANGE IS
IMPLEMENTED.

NCEP CENTRAL OPERATIONS /NCO/ HAS BEGUN PARALLEL TESTING OF THE NAM WITH
THE WRF NMM MODEL. THE OUTPUT FROM THIS PARALLEL RUN WILL BE AVAILABLE
BY THE END OF MARCH AT THE FOLLOWING FTP LOCATION /USE LOWER CASE
LETTERS/:

FTP://FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/NAM/PARA/

AND

FTP://FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/NAWIPS/PARA/NAM.{YYYYMMDD}

ADDITIONAL INFORMATION ON THIS CHANGE INCLUDING PARALLEL DATA
AVAILABILITY\...FTP SERVER PRODUCT CHANGES\...AND OTHER SCIENTIFIC
INFORMATION CAN BE OBTAINED FROM THE FOLLOWING WEB LOCATIONS /USE LOWER
CASE LETTERS/:

HTTP://WWW.NCO.NCEP.NOAA.GOV/PMB/CHANGES/

IF YOU HAVE ANY QUESTIONS CONCERNING THESE CHANGES\...PLEASE

CONTACT:

GEOFF DIMEGO

NCEP\...MESOSCALE MODELING BRANCH

CAMP SPRINGS MARYLAND

PHONE: 301 763 8000 X7221

EMAIL: GEOFF.DIMEGO@NOAA.GOV

OR

ERIC ROGERS

NCEP\...MESOSCALE MODELING BRANCH

CAMP SPRINGS MARYLAND

PHONE: 301 763 8000 X7227

EMAIL: ERIC.ROGERS@NOAA.GOV

OR

BRENT GORDON

NCEP\...PRODUCTION MANAGEMENT BRANCH

CAMP SPRINGS MARYLAND

PHONE: 301 763 8000 X7193

EMAIL: BRENT.GORDON@NOAA.GOV

THIS AND OTHER NWS TECHNICAL IMPLEMENTATION NOTICES ARE AVAILABLE ONLINE
AT /USE LOWER CASE LETTERS/:

[HTTP://WWW.NWS.NOAA.GOV/OM/NOTIF.HTM](http://WWW.NWS.NOAA.GOV/OM/NOTIF.HTM)

\$\$

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