305
NOUS41 KWBC 031815 AAB
PNSWSH
SERVICE CHANGE NOTICE 26-12 UPDATED
NATIONAL WEATHER SERVICE HEADQUARTERS SILVER SPRING MD
115 PM EST TUE MAR 3 2026
TO:SUBSCRIBERS
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS, USERS AND EMPLOYEES
FROM: DAVID MICHAUD, DIRECTOR
NCEP CENTRAL OPERATIONS
SUBJECT: UPDATED: NOTIFICATION OF UPGRADING THE CLIMATE DATA
ASSIMILATION SYSTEM (CDAS) TO THE CONVENTIONAL OBSERVATION
REANALYSIS (CORE) EFFECTIVE MARCH 18, 2026.
UPDATED TO CHANGE THE EFFECTIVE DATE TO MARCH 18 AND TO INCLUDE
ADDITIONAL CDAS PATH ON TGFTP SERVER WHICH WILL NO LONGER BE
AVAILABLE.
EFFECTIVE ON OR ABOUT MARCH 18, 2026, THE NATIONAL CENTERS FOR
ENVIRONMENTAL PREDICTION (NCEP) CENTRAL OPERATIONS (NCO) WILL BE
IMPLEMENTING AN UPGRADE FOR THE CLIMATE DATA ASSIMILATION SYSTEM
(CDAS) TO THE CONVENTIONAL OBSERVATION REANALYSIS (CORE).
IN THE EVENT THAT THE IMPLEMENTATION DATE IS DECLARED A CRITICAL
WEATHER DAY (CWD), AN ENHANCED CAUTION EVENT (ECE), OR OTHER
SIGNIFICANT WEATHER IS OCCURRING OR IS ANTICIPATED TO OCCUR,
IMPLEMENTATION OF THIS CHANGE WILL TAKE PLACE AT 1200 UTC ON THE
NEXT WEEKDAY NOT DECLARED A CWD AND WHEN NO SIGNIFICANT WEATHER
IS OCCURRING.
THE SCIENTIFIC AND TECHNICAL ENHANCEMENTS INCLUDE THE FOLLOWING:
CORE IS A CLIMATE ATMOSPHERIC REANALYSIS FROM 1950-PRESENT, AND
REPLACES CDAS WHICH IS THE REAL-TIME EXTENSION OF THE NCEP/NCAR
REANALYSIS (1948-PRESENT). CORE IS LIKE CDAS, AN ATMOSPHERIC
REANALYSIS THAT USES EXTERNALLY PRODUCED SEA SURFACE TEMPERATURE
(SST), SEA ICE AND SNOW ANALYSES FOR BOUNDARY CONDITIONS.
HOWEVER, CORE USES MORE MODERN VERSIONS OF THESE ANALYSES. CORE
IS A UFS-BASED SYSTEM (CIRCA 2020 CODES) WHICH USES AN ENSEMBLE
KALMAN FILTER TO ASSIMILATE CONVENTIONAL OBSERVATIONS AS WELL AS
ATMOSPHERIC MOTION VECTORS (AMV). CDAS IS A MRF-BASED SYSTEM
(CIRCA 1995 OPERATIONAL CODES) THAT ASSIMILATES CONVENTIONAL
OBSERVATIONS, AS WELL AS AMV AND SATELLITE TEMPERATURE
RETRIEVALS.
THE DATA FILES FOR CORE WILL BE AVAILABLE ON THE NOAA
OPERATIONAL MODEL ARCHIVE AND DISTRIBUTION SERVICE (NOMADS) AT
THE FOLLOWING LOCATION:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/CORE/
THE DATA FILES FOR CDAS WILL NO LONGER BE AVAILABLE AS OF MARCH
18, 2026 AT THE FOLLOWING LOCATIONS:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/CDAS/
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/CDAS2/
HTTPS://TGFTP.NWS.NOAA.GOV/SL.US008001/ST.OPNL/MT.CDAS_CY.00/RD.
YYYYMMDD/PT.GRID_DF.GR2/
WHERE YYYYMMDD IS THE DATE.
SAMPLE CORE FILES ARE AVAILABLE AT THE FOLLOWING LOCATION:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/CORE/PARA/
AT THE PROVIDED CORE URL, NEW CORE FILES HAVE THE FOLLOWING
PATHS AND REGEXES:
/CORE.YYYYMMDD/HH/POST/FLX/CORE.TRRZ.FLX.MEMMMM[.GRIB2,.GRIB2.ID
X]
/CORE.YYYYMMDD/HH/POST/FLX/CORE.TRRZ.FLX.ENSMEAN[.GRIB2,.GRIB2.I
DX]
/CORE.YYYYMMDD/HH/POST/FLX_STATS/CORE.TRRZ.FLX.ENSSTATS[.GRIB2,.
GRIB2.IDX]
/CORE.YYYYMMDD/HH/POST/NCEPPOST/CORE.TRRZ.PGB.ENSMEAN.ANL[.GRIB2
,.GRIB2.IDX]
/CORE.YYYYMMDD/HH/POST/NCEPPOST/CORE.T[HH+06]Z.PGB.ENSMEAN.F003[
.GRIB2,.GRIB2.IDX]
/CORE.YYYYMMDD/HH/POST/SPOST/CORE.TRRZ.SPGB.MEMMMM.ANL[.GRIB2,.G
RIB2.IDX]
/CORE.YYYYMMDD/HH/POST/SPOST/CORE.TRRZ.SPGB.ENSMEAN.ANL[.GRIB2,.
GRIB2.IDX]
/CORE.YYYYMMDD/HH/POST/SPOST_STATS/CORE.TRRZ.SPGB.ENSSTATS[.GRIB
2,.GRIB2.IDX]
WHERE YYYYMMDD IS THE DATE, HH IS THE FORECAST CYCLE
(00,06,12,18), RR IS THE HOUR OF THE REFERENCE TIME (FORECAST
CYCLE + [03,06]), AND MMM IS THE ENSEMBLE MEMBER (001-080
INCLUSIVE).
THE GRIB VERSION 1 FILES HAVE BEEN REPLACED BY GRIB VERSION 2.
FOR QUESTIONS REGARDING THESE MODEL CHANGES, PLEASE CONTACT:
WANQUI WANG
CHIEF, OPERATIONAL MONITORING BRANCH,
NCEP/CLIMATE PREDICTION CENTER
COLLEGE PARK, MD
301-683-3389
WANQIU.WANG@NOAA.GOV
FOR QUESTIONS REGARDING THE DATA FLOW ASPECTS OF THESE DATASETS,
PLEASE CONTACT:
MARGARET CURTIS
NCEP CENTRAL OPERATIONS HPC DATAFLOW TEAM LEAD
NCEP.PMB.DATAFLOW@NOAA.GOV
NATIONAL SERVICE CHANGE NOTICES ARE ONLINE AT:
HTTPS://WWW.WEATHER.GOV/NOTIFICATION
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