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NOUS41 KWBC 151550
PNSWSH
PUBLIC INFORMATION STATEMENT 26-29
NATIONAL WEATHER SERVICE HEADQUARTERS SILVER SPRING MD
1150 AM EDT WED APR 15 2026
TO: SUBSCRIBERS:
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
-OTHER NWS PARTNERS, USERS AND EMPLOYEES
FROM: FANGLIN YANG
CHIEF, PHYSICS AND DYNAMICS DIVISION
ACTING CHIEF, COUPLED MODELING DIVISION
NCEP/ENVIRONMENTAL MODELING CENTER
SUBJECT: SOLICITING PUBLIC COMMENTS THROUGH MAY 15, 2026 ON
THE PROPOSED UPGRADE TO THE GLOBAL FORECAST SYSTEM
THE ENVIRONMENTAL MODELING CENTER (EMC) IS PROPOSING TO UPGRADE
THE NWS OPERATIONAL GLOBAL FORECAST SYSTEM (GFS) AND GLOBAL DATA
ASSIMILATION SYSTEM (GDAS) FROM V16 TO V17 IN OCTOBER 2026.
THIS UPGRADE WILL TRANSITION THE SYSTEM TO A FULLY COUPLED
EARTH-SYSTEM MODELING FRAMEWORK FOR GLOBAL WEATHER PREDICTION,
IMPROVED MODEL FORECAST PERFORMANCE, AND EXPANDED, ENHANCED
PRODUCTS THAT COVER ALL COMPONENTS OF THE EARTH SYSTEM. THE NWS
IS SEEKING COMMENTS ON THE PROPOSED CHANGES TO GFSV17 THROUGH
MAY 15, 2026.
GFSV17 INTRODUCES A COUPLED EARTH-SYSTEM MODEL WITH COMPONENTS
OF THE ATMOSPHERE, LAND, OCEAN, SEA ICE, AND WAVES. PROPOSED
CHANGES TO THE GFSV17 INCLUDE:
- AN INCREASED HORIZONTAL RESOLUTION FROM C768 (13 KM) TO C1152
(9 KM)USING THE FINITE-VOLUME CUBED-SPHERE (FV3) DYNAMIC CORE.
- INTRODUCTION OF FRACTIONAL GRIDS ALONG OCEANIC COASTLINES.
- IMPROVED ATMOSPHERIC AND LAND SURFACE PARAMETERIZATION
SCHEMES, INCLUDING:
(I) REVISIONS TO CONVECTION TRIGGERING, CONVECTIVE RAIN
EVAPORATION, DOWNDRAFT DETRAINMENT, AND IMPROVED SEPARATION
BETWEEN DEEP AND SHALLOW CONVECTION TO REDUCE BIASES AND IMPROVE
CAPE FORECASTS. ADDITIONAL ADVANCEMENTS INCLUDE A NEW
PROGNOSTIC CONVECTIVE UPDRAFT FRACTION PARAMETERIZATION THAT
IMPROVES MJO PREDICTION, STOCHASTIC CONVECTIVE INITIATION AND
ORGANIZATION USING CELLULAR AUTOMATA, AND INCORPORATION OF THE
POSITIVE-DEFINITE MASS-FLUX TRANSPORT AND TRACER TREATMENT TO
REMOVE NEGATIVE TRACER MIXING RATIOS;
(II) A NEW PARAMETERIZATION OF ENVIRONMENTAL WIND SHEAR AND
REVISED PLANETARY BOUNDARY LAYER AND CONVECTION INTERACTION TO
IMPROVE HURRICANE INTENSITY FORECASTS AND MODIFICATION OF THE
BACKGROUND DIFFUSIVITY PROFILE TO BETTER REPRESENT SURFACE
INVERSIONS;
(III) IMPLEMENTATION OF A NEW SEA SPRAY PARAMETERIZATION,
ALONG WITH UPDATES TO MOMENTUM ROUGHNESS OVER THE OCEAN, THERMAL
ROUGHNESS OVER LAND, AND THE MAXIMUM STABILITY LIMIT TO ENHANCE
SURFACE FLUX REPRESENTATION;
(IV) REPLACEMENT OF THE ONE-MOMENT GFDL CLOUD MICROPHYSICS
SCHEME WITH THE HYBRID TWO-MOMENT THOMPSON-EIDHAMMER CLOUD
MICROPHYSICS SCHEME. THIS SCHEME WAS FURTHER ENHANCED TO BETTER
REPRESENT SUPERCOOLED LIQUID CLOUDS AND PRECIPITATION.IN
ADDITION, A SEMI-LAGRANGIAN SEDIMENTATION SCHEME FOR
HYDROMETEORS WAS INTRODUCED TO IMPROVE NUMERICAL STABILITY WHEN
RUNNING THE THOMPSON-EIDHAMMER CLOUD MICROPHYSICS WITH LARGE
TIME STEPS;
(V) IMPROVEMENTS TO THE RAPID RADIATIVE TRANSFER MODEL FOR
GCMS (RRTMG) RADIATION, INCLUDING THE INTRODUCTION OF A NEW
MODERN-ERA RETROSPECTIVE ANALYSIS FOR RESEARCH AND APPLICATIONS
VERSION 2 (MERRA-2) AEROSOL CLIMATOLOGY, UPDATED CLOUD-RADIATION
INTERACTION, AND REFINEMENTS TO ADDRESS EXCESSIVE NET SHORTWAVE
RADIATION TO THE OCEAN AT LOW SUN ANGLES;
(VI) REPLACEMENT OF THE NOAH LAND SURFACE MODEL (LSM) WITH THE
NOAH LAND SURFACE MODEL WITH MULTI-PARAMETERIZATION (NOAH-MP);
(VII) UPDATES AND UNIFICATION OF OROGRAPHIC AND NON-OROGRAPHIC
GRAVITY WAVE DRAG (GWD) PARAMETERIZATIONS AND MOUNTAIN BLOCKING
EFFECTS, ALONG WITH THE INTRODUCTION OF TURBULENT OROGRAPHIC
FORM DRAG;
(VIII) INTRODUCTION OF FRACTIONAL GRID COMPOSITING OF ALBEDO
AND EMISSIVITY TO IMPROVE ATMOSPHERE-LAND COUPLING STABILITY AND
CONSISTENCY ALONG COASTLINES; AND
- INTRODUCTION OF THE MODULAR OCEAN MODEL (MOM6) ON A QUARTER-
DEGREE TRIPOLAR GRID FOR THE OCEAN COMPONENT.
- INTRODUCTION OF THE COMMUNITY ICE CODE (CICE6) MODEL ON A
QUARTER-DEGREE TRIPOLAR GRID FOR THE SEA ICE COMPONENT.
- CONTINUED USE OF THE WAVEWATCH III MODEL FOR THE WAVE
COMPONENT WHILE INTRODUCING AN UNSTRUCTURED GRID. THE WAVE
COMPONENT WILL RECEIVE ICE AND CURRENT AS INPUTS THROUGH THE
COUPLED SYSTEM AND PROVIDE FEEDBACK TO THE ATMOSPHERE AND OCEAN
COMPONENTS.
- CONTINUED USE OF THE UNIFIED FORECAST SYSTEM WEATHER MODEL AS
THE OVERALL FRAMEWORK FOR ALL COUPLED EARTH SYSTEM COMPONENTS.
- INTRODUCTION OF THE COMMUNITY MEDIATOR FOR EARTH PREDICTION
SYSTEMS (CMEPS) FOR COUPLING BETWEEN EARTH SYSTEM COMPONENTS,
WITH CONTINUED USE OF THE NATIONAL UNIFIED OPERATIONAL
PREDICTION CAPABILITY (NUOPC) LAYER OF THE EARTH SYSTEM MODELING
FRAMEWORK (ESMF). THESE EFFORTS BENEFITTED FROM COLLABORATION
WITH NOAA/GFDL, NCAR, AND NASA.
- OPTIMIZATION OF THE COMPUTATIONAL PERFORMANCE OF THE FULLY
COUPLED APPLICATION.
- ADVANCEMENT OF THE GLOBAL WORKFLOW, AN END-TO-END PORTABLE
SYSTEM DESIGNED TO RUN THE FULLY COUPLED UFS EARTH-SYSTEM MODEL
FOR DETERMINISTIC AND ENSEMBLE APPLICATIONS ACROSS SCALES,
INCLUDING GFSV17 FOR MEDIUM-RANGE WEATHER PREDICTION.
GDASV17 WILL INTRODUCE NEW DATA ASSIMILATION COMPONENTS TO
PROVIDE INITIAL CONDITIONS FOR THE NEW MODELING COMPONENTS.
THESE NEW DATA ASSIMILATION ALGORITHMS WILL USE THE JOINT EFFORT
FOR DATA ASSIMILATION INTEGRATION (JEDI) FRAMEWORK. PROPOSED
CHANGES TO THE GDASV17 INCLUDE:
- UPGRADE OF THE GSI-BASED HYBRID 4DENVAR ATMOSPHERIC DATA
ASSIMILATION SCHEME TO A MULTI-SCALE ALGORITHM WITH SCALE-
DEPENDENT LOCALIZATION.
- REPLACEMENT OF THE GLOBAL LAND DATA ASSIMILATION SYSTEM
(GLDAS) WITH A SOIL TEMPERATURE AND SOIL MOISTURE ANALYSIS AS
PART OF THE EXISTING GSI-BASED ATMOSPHERIC LOCAL ENSEMBLE
TRANSFORM KALMAN FILTER (LETKF). OBSERVATIONS ASSIMILATED ARE
SCREEN-LEVEL TEMPERATURE AND MOISTURE OBSERVATIONS.
- INTRODUCTION OF SNOW DATA ASSIMILATION USING A 2DVAR ALGORITHM
WITHIN THE JEDI FRAMEWORK. OBSERVATIONS ASSIMILATED ARE STATION
OBSERVATIONS OF SNOW DEPTH AND SNOW AND ICE MAPPING SYSTEM (IMS)
SNOW COVER OBSERVATIONS.
- INTRODUCTION OF OCEAN AND SEA ICE DATA ASSIMILATION USING A
JEDI-BASED 3DVAR-FGAT ALGORITHM. OBSERVATIONS ASSIMILATED ARE
ALONG-TRACK SEA SURFACE HEIGHT FROM JASON-3, SENTINEL-6 MICHAEL
FREILICH, SARAL/ALTIKA, AND CRYOSAT-2; SEA SURFACE TEMPERATURE
FROM VIIRS INSTRUMENTS ON SUOMI-NPP, NOAA-20, AND NOAA-21 AND
AVHRR INSTRUMENTS ON NOAA-18, NOAA-19, METOP-B, AND METOP-C; SEA
ICE CONCENTRATION FROM THE AMSR2 PASSIVE MICROWAVE SENSOR ON
GCOM-W1; AND IN-SITU TEMPERATURE AND SALINITY OBSERVATIONS FROM
ARGO FLOATS AND SURFACE DRIFTERS.
AS A RESULT OF THE EXPANDED PRODUCTS IN GFSV17 SOME OF THE
EXISTING PRODUCTS WILL BE DISCONTINUED. WE WILL ISSUE A SEPARATE
PUBLIC NOTICE ON PRODUCT REMOVALS ASSOCIATED WITH THE GFSV17
UPGRADE.
SIGNIFICANT FOLDER DIRECTORY STRUCTURE AND NAME CHANGES ARE
PLANNED TO HELP IMPROVE ORGANIZATION AND CLARITY OF FILES AS WE
ADD MORE COMPONENTS. DETAILS WILL BE SHARED IN A SERVICE CHANGE
NOTICE BEFORE IMPLEMENTATION.
THE NWS WILL EVALUATE ALL COMMENTS TO DETERMINE WHETHER TO
PROCEED WITH THE PROPOSED UPGRADE. IF APPROVED, A SERVICE
CHANGE NOTICE WILL BE ISSUED 30 DAYS BEFORE THE MODEL
IMPLEMENTATION DATE. PLEASE SUBMIT COMMENTS AND QUESTIONS ON THE
PROPOSED GFSV17 UPGRADE TO:
EMAIL: GFS.FEEDBACK@NOAA.GOV
GOOGLE FORM: SOLICITING COMMENTS ON THE PROPOSED UPGRADE TO THE
GLOBAL FORECAST SYSTEM AT:
HTTPS://DOCS.GOOGLE.COM/FORMS/D/E/1FAIPQLSCKNKARCMR7QELBOHI3EANJ
F6XQBVMMKPW8DQS0TLLRIMKFCQ/VIEWFORM
FOR QUESTIONS REGARDING THE DATA FLOW ASPECTS, PLEASE CONTACT:
MARGARET CURTIS
NWS CENTRAL OPERATIONS DATAFLOW TEAM LEAD
COLLEGE PARK, MD
NCEP.PMB.DATAFLOW@NOAA.GOV
NATIONAL PUBLIC INFORMATION STATEMENTS ARE ONLINE AT:
HTTPS://WWW.WEATHER.GOV/NOTIFICATION/
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