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NOUS41 KWBC 022110 AAA
PNSWSH
SERVICE CHANGE NOTICE 26-48 UPDATED
NATIONAL WEATHER SERVICE HEADQUARTERS SILVER SPRING MD
310 PM EDT TUE JUNE 2 2026
TO: SUBSCRIBERS:
- NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS, USERS AND EMPLOYEES
FROM: DAVID MICHAUD, DIRECTOR
NWS CENTRAL OPERATIONS
SUBJECT: UPDATED: IMPLEMENTATION OF THE RAPID REFRESH FORECAST
SYSTEM (RRFS) AND RRFS ENSEMBLE FORECAST SYSTEM (REFS):
EFFECTIVE AUG 31, 2026
UPDATED TO REFLECT A CHANGE TO THE PARALLEL DATA FEED; NOW
AVAILABLE ON JULY 7, 2026.
EFFECTIVE ON OR ABOUT AUG 31, 2026, BEGINNING WITH THE 1200
COORDINATED UNIVERSAL TIME (UTC) RUN, THE NATIONAL CENTERS FOR
ENVIRONMENTAL PREDICTION (NCEP) WILL IMPLEMENT TWO NEW MODELING
SYSTEMS, THE RAPID REFRESH FORECAST SYSTEM (RRFS) AND RRFS
ENSEMBLE FORECAST SYSTEM (REFS).
THE RRFS AND REFS WILL REPLACE NAM, HREF, SREF, AND HIRESW. A
FULL LIST OF PRODUCTS BEING RETIRED IS AVAILABLE IN SCN 26-47.
THE RRFS AND REFS PRODUCTION IMPLEMENTATION AND THE RETIREMENT
OF THE LEGACY MODELS WILL OCCUR ON THE SAME DAY. IN THE EVENT
THAT THE IMPLEMENTATION DATE IS DECLARED A CRITICAL WEATHER DAY
(CWD), AN ENHANCED CAUTION EVENT, 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.
A REAL-TIME PARALLEL FEED OF RRFS AND REFS WILL BE AVAILABLE ON
OR ABOUT JULY 7, 2026, ON NOMADS FOR BOTH NCEP WEB SERVICES AND
NOAAPORT OUTPUT HERE:
PRE-IMPLEMENTATION DATA LOCATION STARTING ON OR ABOUT JULY 7,
2026:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/RRFS/PARA/
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/REFS/PARA/
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/PARA/NOAAPORT/RRF
S/
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/PARA/NOAAPORT/REF
S/
POST-IMPLEMENTATION DATA LOCATION AUG 31, 2026:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/RRFS/PROD/
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/REFS/PROD/
THE DEVELOPMENT OF THE RRFS AND REFS WAS A COORDINATED EFFORT
BETWEEN THE ENVIRONMENTAL MODELING CENTER AND NOAA'S OFFICE OF
OCEANIC AND ATMOSPHERIC RESEARCH (OAR), SPECIFICALLY THE GLOBAL
SYSTEMS LABORATORY, AND A WIDE-RANGING NETWORK OF PARTNERS. THIS
COLLABORATION INCLUDED OTHER NWS ENTITIES, ACADEMIC
INSTITUTIONS, OTHER FEDERAL AGENCIES, AND INTERNATIONAL
PARTNERS.
1) RRFS MODELING SYSTEM
THIS TRANSITION TO RRFS WILL PROVIDE AN HOURLY UPDATED MODELING
SYSTEM COVERING THE NORTH AMERICA REGION AT 3 KM HORIZONTAL GRID
SPACING, WHICH, COMBINED WITH THE ASSOCIATED MODEL RETIREMENTS,
WILL GREATLY UNIFY AND SIMPLIFY THE "CONVECTIVE SCALE"
(APPROXIMATELY 3 KM GRID SPACING) SUITE OF REGIONAL MODELS
WITHIN THE NWS OPERATIONAL MODELING SUITE.
AS A DETERMINISTIC SYSTEM RUNNING TO 84 H FOR THE 00/06/12/18
UTC CYCLES, AND TO 18 H FOR OTHER HOURLY CYCLES, THE RRFS WILL
FULLY RETIRE THE NORTH AMERICAN MESOSCALE (NAM), AND RETIRE THE
HIGH-RESOLUTION WINDOW (HIRESW) ASIDE FROM THE GUAM DOMAIN WHICH
WILL REMAIN. AS AN ENSEMBLE FORECAST SYSTEM RUNNING TO 60 H FOR
THE 00/06/12/18 UTC CYCLES, THE RRFS ENSEMBLE FORECAST SYSTEM
(REFS) WILL FULLY RETIRE THE HIGH-RESOLUTION ENSEMBLE FORECAST
(HREF) SYSTEM.
A) DETERMINISTIC FORECAST DETAILS
THE DETERMINISTIC RRFS RUNS OVER A FULL NORTH AMERICA (NA)
DOMAIN AT 3 KM GRID SPACING, AND PROVIDES SUBSET GRID OUTPUT AT
3 KM GRID SPACING FOR THE CONTIGUOUS UNITED STATES (CONUS) AND
ALASKA (AK), AND AT 2.5 KM GRID SPACING FOR HAWAII (HI) AND
PUERTO RICO (PR). THE RRFS ALSO PROVIDES OUTPUT FROM A SEPARATE
RELOCATABLE 1.5 KM RRFS FIRE WEATHER RUN, WITH OUTPUT PROVIDED
OVER A 5 X 5-DEGREE ROTATED LATITUDE LONGITUDE REGION.
DETERMINISTIC RRFS OUTPUT IS ORGANIZED AS FOLLOWS:
UNDER RRFS/V1.0
RRFS.YYYYMMDD/CC/RRFS.TCCZ.PRSLEV.3KM.FFFF.{CONUS|AK}.GRIB2
RRFS.YYYYMMDD/CC/RRFS.TCCZ.PRSLEV.2P5KM.FFFF.{HI|PR}.GRIB2
RRFS.YYYYMMDD/CC/RRFS.TCCZ.2DFLD.3KM.FFFF.{CONUS|AK}.GRIB2
RRFS.YYYYMMDD/CC/RRFS.TCCZ.2DFLD.2P5KM.FFFF.{HI|PR}.GRIB2
RRFS.YYYYMMDD/CC/RRFS.TCCZ.2DFLD.3KM.SUBH.FFFF.{CONUS|AK}.GRIB2
RRFS.YYYYMMDD/CC/RRFS.TCCZ.2DFLD.2P5KM.SUBH.FFFF.{HI|PR}.GRIB2
FIREWX.YYYYMMDD/CC/RRFS.TCCZ.PRSLEV.1P5KM.FFFF.FIREWX_LCC.GRIB2
FIREWX.YYYYMMDD/CC/RRFS.TCCZ.2DFLD.1P5KM.FFFF.FIREWX_LCC.GRIB2
A FULL DESCRIPTION OF RRFS PRODUCTS INCLUDING VARIABLES AND
ENCODING IS AVAILABLE AT:
HTTPS://WWW.NCO.NCEP.NOAA.GOV/PMB/PRODUCTS/RRFS/
B) ENSEMBLE FORECAST DETAILS
THE RRFS PRODUCES FIVE ENSEMBLE FORECAST MEMBERS RUNNING TO 60 H
FOR THE 00/06/12/18 UTC CYCLES, OVER THE SAME NA REGION AS THE
DETERMINISTIC RRFS. THESE MEMBERS UTILIZE DIFFERENT INITIAL
CONDITIONS, LATERAL BOUNDARY CONDITIONS, AND MODEL PHYSICS
RELATIVE TO THE DETERMINISTIC FORECAST TO BETTER COVER THE RANGE
OF FORECAST POSSIBILITIES.
2) REFS MODELING SYSTEM
THE REFS IS AN ENSEMBLE PRODUCT GENERATION SYSTEM THAT COMBINES
THE FORECAST OUTPUT FROM THE CURRENT AND 6 H OLD CYCLES OF RRFS
DETERMINISTIC (SECTION 1A) AND ENSEMBLE (SECTION 1B) SYSTEMS TO
GENERATE ENSEMBLE PRODUCTS. FOR THE ALASKA AND CONUS REFS
DOMAINS, THE HRRR PROVIDES TWO ADDITIONAL MEMBERS (FROM CURRENT
AND 6 H OLD CYCLES).
THE REFS IS A REPLACEMENT FOR THE HIGH-RESOLUTION ENSEMBLE
FORECAST (HREF) SYSTEM, AND SHARES SIMILARITIES WITH THE HREF IN
TERMS OF PRODUCT TYPES. REFS DOES DIFFER FROM HREF IN TERMS OF
MEMBERSHIP, AND PRODUCES PRODUCTS TO 60 H, WHILE HREF GENERATES
PRODUCTS TO 48 H. ALSO, REFS GENERATES PRODUCTS FOR ALL DOMAINS
(CONUS, AK, HI, PR) FOR THE 00/06/12/18 UTC CYCLES, WHILE HREF
GENERATES PRODUCTS TWICE DAILY FOR NON-CONUS DOMAINS (AK AND PR
DOMAINS AT 06Z/18Z, AND HI AT 00Z/12Z).
REFS ENSEMBLE PRODUCT OUTPUT IS ORGANIZED AS FOLLOWS UNDER
REFS/V1.0:
REFS.YYYYMMDD/CC/ENSPROD/REFS.TCCZ.${TYPE}.FFF.${DOM}.GRIB2
WHERE DOM IS THE DOMAIN (CONUS, AK, HI, PR)
AND WHERE TYPE IS THE PRODUCT TYPE LISTED AND DESCRIBED BELOW
MEAN: SIMPLE ENSEMBLE MEAN
SPRD: ENSEMBLE SPREAD
PMMN: PROBABILITY-MATCHED MEAN
LPMM: LOCALIZED PROBABILITY-MATCHED MEAN
AVRG: A COMBINATION OF THE PMMN AND MEAN FIELDS
PROB: PROBABILISTIC OUTPUT
EAS: ENSEMBLE AGREEMENT SCALE PROBABILISTIC OUTPUT
REFS.YYYYMMDD/CC/ENSPROD/REFS.TCCZ.FFRI.FFF.CONUS.GRIB2
FFRI: FLASH FLOOD AND RECURRENCE INTERVAL EXCEEDANCE
PROBABILITIES (CONUS ONLY)
DETAILED INFORMATION ABOUT THE FILE CONTENTS INCLUDING VARIABLES
AND ENCODING IS AVAILABLE AT:
HTTPS://WWW.NCO.NCEP.NOAA.GOV/PMB/PRODUCTS/REFS/
NCEP URGES ALL USERS TO ENSURE THEIR DECODERS CAN HANDLE CHANGES
IN CONTENT ORDER, CHANGES IN THE SCALING FACTOR COMPONENT WITHIN
THE PRODUCT DEFINITION SECTION (PDS) OF THE GRIB FILES, AND
VOLUME CHANGES. THESE ELEMENTS MAY CHANGE WITH FUTURE NCEP MODEL
IMPLEMENTATIONS. NCEP WILL MAKE EVERY ATTEMPT TO ALERT USERS TO
THESE CHANGES BEFORE IMPLEMENTATION.
FOR QUESTIONS REGARDING THE IMPLEMENTATION OF RRFS AND REFS, A
PUBLIC WEBINAR WILL BE HOSTED ON JUNE 25TH. TO SIGN UP PLEASE
USE THE FOLLOWING FORM: HTTPS://FORMS.GLE/UGFQEVSN716RENX67.
ADDITIONAL QUESTIONS NOT ANSWERED IN THE WEBINAR CAN BE DIRECTED
TO:
THE ENVIRONMENTAL MODELING CENTER
RRFS FEEDBACK
RRFS.FEEDBACK@NOAA.GOV
FOR QUESTIONS ABOUT DATAFLOW ASPECTS OF THESE IMPLEMENTATIONS,
PLEASE CONTACT:
MARGARET CURTIS
NCEP CENTRAL OPERATIONS HPC DATAFLOW TEAM LEAD
NCEP.PMB.DATAFLOW@NOAA.GOV
NATIONAL SERVICE CHANGE NOTICES ARE ONLINE AT:
WWW.WEATHER.GOV/NOTIFICATION/
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