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NOUS41 KWBC 151430
PNSWSH
PUBLIC INFORMATION STATEMENT 25-45
NATIONAL WEATHER SERVICE HEADQUARTERS SILVER SPRING MD
1039 AM EDT TUE JUL 15 2025
TO: SUBSCRIBERS:
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS, USERS AND EMPLOYEES
FROM: GEOFF MANIKIN
CHIEF, STATISTICAL MODELING DIVISION
NWS OFFICE OF SCIENCE AND TECHNOLOGY INTEGRATION
METEOROLOGICAL DEVELOPMENT LABORATORY
SUBJECT: SOLICITING COMMENTS ON THE PROPOSED UPGRADE OF THE
NATIONAL BLEND OF MODELS THROUGH NOVEMBER 21, 2025
THE STATISTICAL MODELING DIVISION (SMD) OF THE METEOROLOGICAL
DEVELOPMENT LABORATORY (MDL) IS PROPOSING TO UPDATE THE NATIONAL
BLEND OF MODELS (NBM) IN APRIL OF 2026. THE NWS IS SEEKING
COMMENTS ON THIS PROPOSED UPGRADE THROUGH NOVEMBER 21, 2025. IF
APPROVED, A SERVICE CHANGE NOTICE (SCN) WILL BE ISSUED AT LEAST
30 DAYS PRIOR TO THE IMPLEMENTATION OF THESE UPGRADED PRODUCTS
WITH MORE DETAILED INFORMATION.
NBM VERSION 5.0 IS A SIGNIFICANT UPGRADE OVER THE OPERATIONAL
VERSION 4.3 AND WILL CONTINUE TO FILL EXISTING PRODUCT GAPS
REQUESTED BY THE FIRE WEATHER, WINTER, WATER RESOURCES,
AVIATION, PUBLIC, AND TROPICAL NWS SERVICE PROGRAMS.
SEVERAL HIGHLIGHTS ASSOCIATED WITH THIS UPCOMING RELEASE INCLUDE
THE FOLLOWING:
(1) GENERATION OF QUANTILE-MAPPED (QM) QUANTITATIVE
PRECIPITATION FORECASTS (QPF) AND PROBABILITY OF PRECIPITATION
GUIDANCE (POP) REPLACES THE CURRENT EQUAL WEIGHTING OF ALL
INPUTS WITH AN APPROACH THAT GIVES MORE (PRE-DEFINED) WEIGHT TO
HIGHER-RESOLUTION INPUTS (CONUS, ALASKA, HAWAII, PUERTO RICO,
AND OCEANIC DOMAINS). THE MULTI-MODEL ENSEMBLE BIAS CORRECTION
(MMEBC) QPF PRODUCT FROM THE WEATHER PREDICTION CENTER (WPC) IS
ADDED AS AN INPUT (CONUS).
(2) ADDITION OF A NEW 24H PROBABILITY MATCHED MEAN (PMM)
QUANTITATIVE PRECIPITATION PRODUCT (ONLY COMPRISING HIGH-
RESOLUTION MODELS) FOR THE CONUS AND ALASKA DOMAINS.
(3) REPLACEMENT OF DECAYING AVERAGE COMPUTATIONS OF
INSTANTANEOUS TEMPERATURE, DEW POINT TEMPERATURE, RELATIVE
HUMIDITY, AND 12-HOUR MAXIMUM AND MINIMUM RELATIVE HUMIDITY (RH)
WITH QM. THIS ALLOWS FOR THE COMPUTATION OF ASSOCIATED
PERCENTILE AND EXCEEDANCE VALUES (CONUS, ALASKA, HAWAII, PUERTO
RICO, AND GUAM DOMAINS).
(4) ADDITION OF JOINT FIRE WEATHER PROBABILITIES FOR THE
OCCURRENCE OF VARIOUS COMBINATIONS OF WIND SPEEDS AND RH
THRESHOLDS (CONUS, ALASKA, HAWAII, PUERTO RICO, GUAM DOMAINS).
(5) ADDITION OF QM 10-METER WIND SPEED AND WIND GUST GUIDANCE
FOR THE ALASKA, HAWAII, PUERTO RICO, AND GUAM DOMAINS.
(6) ADDITION OF PROBABILISTIC QM BIAS-CORRECTED WIND SPEED AND
WIND GUST ALONG WITH DECAYING AVERAGE BIAS CORRECTED
PROBABILISTIC DEW POINT TEMPERATURE, 6-HOUR MAXIMUM AND MINIMUM
2-METER TEMPERATURE, AND SKY COVER FOR THE OCEANIC DOMAIN.
(7) ADDITION OF DETERMINISTIC AND PROBABILISTIC DECAYING AVERAGE
BIAS-CORRECTED PRECIPITABLE WATER GUIDANCE FOR THE CONUS.
(8) ADDITION OF A NEW CONUS 24H, 48H, AND 72H CALIBRATED SNOW
EXCEEDANCE PRODUCT ALONG WITH A 24H PROBABILITY MATCHED MEAN
DETERMINISTIC SNOW AND ICE GUIDANCE (ONLY COMPRISING HIGH-
RESOLUTION MODELS) FOR THE CONUS AND ALASKA DOMAINS.
(9) ADDITION OF A NEW DETERMINISTIC SNOW DEPTH PRODUCT AND
CORRESPONDING EXCEEDANCE PROBABILITIES TO ADDRESS FIRE WEATHER
CONCERNS OVER THE CONUS AND ALASKA DOMAINS.
(10) ADDITION OF PROBABILISTIC APPARENT TEMPERATURE FOR THE
CONUS, ALASKA, HAWAII, PUERTO RICO, AND GUAM DOMAINS AND
DETERMINISTIC APPARENT TEMPERATURE FOR THE OCEANIC DOMAIN.
(11) INTRODUCTION OF A NEW “PERCENTILE PICKING” APPROACH TO
GENERATE DETERMINISTIC WIND SPEED AND WIND GUST FORECASTS RATHER
THAN USING THE MEAN QM VALUE. THIS METHODOLOGY MODULATES THE QM
MEAN 10-METER WIND SPEED AND WIND GUSTS FORECASTS AWAY FROM THE
MEAN VALUE AS A FUNCTION OF WHERE THE MEAN FORECAST LIES
RELATIVE TO THE MODEL DISTRIBUTION AND PAST CLIMATOLOGY (CONUS,
ALASKA, HAWAII, PUERTO RICO, AND OCEANIC DOMAINS).
(12) ADDING THE CANADIAN GLOBAL AND REGIONAL DETERMINISTIC AND
ENSEMBLE MODELS AS INPUTS TO THE WINTER WEATHER SUITE ALONG WITH
MINOR CHANGES TO THE CRITERIA FOR CONVERTING SNOW AND ICE TO
RAIN IN THE DOWNSCALING APPROACH. WITH RESPECT TO PROBABILISTIC
SNOWFALL ACCUMULATION, AN UNEQUAL MODEL WEIGHTING METHOD IS NOW
APPLIED (SIMILAR TO WHAT IS NOTED IN (1)) WHEN CALCULATING THE
CUMULATIVE DISTRIBUTION FUNCTIONS FOR GENERATING PERCENTILE AND
EXCEEDANCE VALUES (CONUS AND ALASKA DOMAINS).
(13) REPLACEMENT OF THE LOW-RESOLUTION DETERMINISTIC ECMWF (0.25
DEG) AND ECMWF ENSEMBLE GUIDANCE (0.50 DEG) WITH 0.10 DEG AND
0.20 DEG DATA, RESPECTIVELY. REPLACEMENT OF THE LOWER
RESOLUTION GDPS (25 KM) AND REPS (15KM) CANADIAN MODEL DATA WITH
HIGHER HORIZONTAL RESOLUTION DATA OF 15KM AND 10KM,
RESPECTIVELY.
(14) AN UPDATE TO THE APPROACH USED TO BIAS CORRECT SIGNIFICANT
WAVE HEIGHTS BY LEVERAGING QM TO REPLACE THE OPERATIONAL
DECAYING AVERAGE ALGORITHM AND INCREASING THE NUMBER OF MODEL
INPUTS FROM 13 TO APPROXIMATELY 120 (CONUS, ALASKA, HAWAII,
PUERTO RICO, GUAM, AND OCEANIC DOMAINS).
(15) REPLACEMENT OF THE DETERMINISTIC CEILING HEIGHT AND
VISIBILITY (C&V) GUIDANCE FOR THE HAWAIIAN DOMAIN WITH A NEW
C&V PRODUCT FOR HAWAII THAT WILL MIRROR THE GRIDDED “MELD”
LOCALIZED AVIATION MOS PROGRAM (LAMP) APPROACH USED OVER CONUS
AND ALASKA, AND WILL INCORPORATE A GRIDDED OBSERVATIONAL
ANALYSIS, RAP, GFS, AND ECMWF AS INPUTS. THE PRODUCT LEVERAGES
A RANDOM FOREST TECHNIQUE TO DERIVE “PSEUDO” OBSERVATIONS OVER
THE HAWAIIAN ISLANDS TO HELP INFORM THE GRIDDED OBSERVATIONAL
ANALYSIS (AN IMPORTANT COMPONENT IN THE FIRST SIX HOURS).
(16) REMOVAL OF THE HAINES INDEX PRODUCT (CONUS, ALASKA, HAWAII,
AND PUERTO RICO DOMAINS).
(17) EXTENSION OF HOURLY GUIDANCE FROM 36 HOURS TO 48 HOURS
(EXCLUDING CEILING, VISIBILITY, AND THUNDERSTORM COVERAGE).
(18) USAGE OF THE EUROPEAN CENTRE FOR MEDIUM-RANGE WEATHER
FORECASTS ARTIFICIAL INTELLIGENCE/INTEGRATED FORECASTING SYSTEM
(ECAIFS) AS AN INPUT FOR TEMPERATURE, DEW POINT, WIND SPEED AND
GUST, AND QPF (ALL DOMAINS, EXCEPT FOR QPF OVER GUAM).
(19) ADDITION OF PROBABILISTIC CONVECTIVE AVAILABLE POTENTIAL
ENERGY (CAPE) OVER THE CONUS: 10TH, 50TH, AND 90TH WEIGHTED
PERCENTILES.
IT IS ANTICIPATED THAT THESE UPGRADES WILL BENEFIT THE NWS IN
ITS MISSION TOWARDS BETTER IMPACT-BASED DECISION SUPPORT
SERVICES (IDSS).
PUBLICLY ACCESSIBLE NBM GRIB2 FILES WILL BE AVAILABLE FOR
DOWNLOAD IN NOMADS APPROXIMATELY 30 DAYS PRIOR TO
IMPLEMENTATION. FURTHER DETAILS CONCERNING THE LOCATION OF THE
DATA WILL BE PROVIDED CLOSER TO THE IMPLEMENTATION DATE WITH AN
UPDATED SCN.
A SLIDE DECK DETAILING THE NBM V5.0 UPDATES AND IMPROVEMENTS CAN
BE FOUND UNDER THE VERSION 5.0 SECTION OF THE NBM VERSIONS
WEBPAGE:
HTTPS://VLAB.NOAA.GOV/WEB/MDL/NBM-VERSIONS
ALL OR A PORTION OF THE NBM TEXT BULLETINS CAN BE OBTAINED BY
VISITING AN INTERACTIVE GRAPHICAL USER INTERFACE (GUI):
HTTPS://BLEND.MDL.NWS.NOAA.GOV/NBM-TEXT
MANY OF THE NBM V5.0 PRODUCTS CAN BE VIEWED ON OUR QUICK VIEWER
LOCATED AT:
HTTPS://BLEND.MDL.NWS.NOAA.GOV/NBM-IMAGES
THE NWS WILL EVALUATE ALL COMMENTS ON THIS NBM UPGRADE TO
DETERMINE WHETHER OR NOT TO PROCEED WITH THIS UPGRADE.
FOR PROVIDING COMMENTS ON THE ABOVE CHANGES, PLEASE USE THE
FEEDBACK FORM WHICH CAN BE ACCESSED VIA THIS LINK:
HTTPS://DOCS.GOOGLE.COM/FORMS/D/13MPUQ_KDMAMWX4NRJZKOUVUYMKC6UVG
BORGHKOLRGJE/
ALTERNATIVELY, ANY QUESTIONS, COMMENTS OR REQUESTS REGARDING
THIS IMPLEMENTATION SHOULD BE DIRECTED TO THE CONTACTS BELOW.
WE WILL REVIEW ANY FEEDBACK AND DECIDE WHETHER OR NOT TO
PROCEED.
FOR QUESTIONS REGARDING THE IMPLEMENTATION OF NBM GUIDANCE,
PLEASE CONTACT:
GEOFF MANIKIN
CHIEF, STATISTICAL MODELING DIVISION
MDL/SILVER SPRING, MARYLAND
GEOFFREY.MANIKIN@NOAA.GOV
OR
DAVID RUDACK
NBM PROJECT LEAD
MDL/SILVER SPRING, MD
DAVID.RUDACK@NOAA.GOV
NATIONAL PUBLIC INFORMATION STATEMENTS ARE ONLINE AT:
HTTPS://WWW.WEATHER.GOV/NOTIFICATION/
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