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NOUS41 KWBC 281345 AAA
PNSWSH
SERVICE CHANGE NOTICE 26-41 UPDATED
NATIONAL WEATHER SERVICE HEADQUARTERS SILVER SPRING MD
945 AM EDT THU MAY 28 2026
TO: SUBSCRIBERS:
-NOAA WEATHER WIRE SERVICE
-EMERGENCY MANAGERS WEATHER INFORMATION NETWORK
-NOAAPORT
OTHER NWS PARTNERS AND NWS EMPLOYEES
FROM: MARK WILLIS
NWS OFFICE OF SCIENCE AND TECHNOLOGY INTEGRATION
METEOROLOGICAL DEVELOPMENT LABORATORY
SUBJECT: UPDATED: PROBABILISTIC TROPICAL CYCLONE STORM SURGE (P-
SURGE) MODEL UPGRADE: EFFECTIVE JUNE 2, 2026
UPDATED TO REFLECT THE NEW IMPLEMENTATION DATE OF JUNE 2, 2026.
EFFECTIVE ON OR ABOUT JUNE 2, 2026, STARTING WITH THE 1200
COORDINATED UNIVERSAL TIME (UTC) CYCLE, THE NATIONAL CENTERS FOR
ENVIRONMENTAL PREDICTION (NCEP) WILL UPGRADE THE PROBABILISTIC
TROPICAL CYCLONE STORM SURGE MODEL (P-SURGE) TO VERSION 3.2.
P-SURGE IS BASED ON AN ENSEMBLE OF SEA, LAKE, AND OVERLAND
SURGES FROM HURRICANES (SLOSH) MODEL RUNS WHICH ARE DERIVED FROM
THE NATIONAL HURRICANE CENTER (NHC) OFFICIAL ADVISORY ALONG WITH
NHC'S HISTORICAL ERRORS IN FORECASTS OF THE STORM'S TRACK, SIZE,
AND INTENSITY.P-SURGE CURRENTLY IS RUN ON A CASE-BY-CASE BASIS
IN ADVANCE OF HURRICANES AND TROPICAL STORMS THAT MAY IMPACT THE
ATLANTIC AND GULF COASTS OF THE CONTIGUOUS UNITED STATES
(CONUS), PUERTO RICO AND THE U.S. VIRGIN ISLANDS, AND HAWAII.
P-SURGE VERSION 3.2 INCLUDES THE FOLLOWING UPDATES:
A. REPLACE THE UNDERLYING COMPUTATIONAL GRID FOR PUERTO RICO
WITH A HIGHER RESOLUTION ONE. THE RESOLUTION OF THE NEW GRID
WILL BE ~400M AT THE SHORELINE ENABLING P-SURGE TO PROPERLY
SUPPORT THE 625M OUTPUT GRID.
B. ADJUST HOW THE CODE DETECTS LAND WHEN CONSTRUCTING THE
PRIMARY STORM PARAMETERIZATION THEREBY ALLOWING THE CODE TO
PROPERLY DECAY THE STORM. THIS ENABLES IT TO HOLD THE PREVIOUS
OVER-OCEAN FORECASTS FOR BOTH MAXIMUM WIND SPEED AND RADIUS OF
MAXIMUM WINDS CONSTANT UNTIL LANDFALL WHICH WILL IMPROVE
FORECAST-TO-FORECAST CONSISTENCY. THIS ADJUSTMENT IS ONLY BEING
APPLIED TO THE CONUS FOR THIS IMPLEMENTATION, WITH OTHER REGIONS
TO BE CONSIDERED IN THE FUTURE.
C. EXPERIMENTALLY GENERATE EXPERIMENTAL STANDARD HYDROLOGIC
EXCHANGE FORMAT (SHEF) PRODUCTS FOR 10, 50, AND 90% EXCEEDANCES
AT STATIONS. THE DATA WILL BE AVAILABLE VIA NOAA'S OPERATIONAL
MODEL ARCHIVE AND DISTRIBUTION SYSTEM (NOMADS) WITH THIS
IMPLEMENTATION. FOLLOW-ON IMPLEMENTATIONS WILL GATHER WMO
HEADERS TO ENABLE IT TO BE PLACED ON THE SATELLITE BROADCAST
NETWORK (SBN).
D. UPDATE THE NHC FORECAST ERROR STATISTICS USED FOR THE
ATLANTIC (I.E., THE CONUS AND PUERTO RICO DOMAINS) AND CENTRAL
PACIFIC (I.E., THE HAWAIIAN DOMAINS). THIS ADDS FOUR NEWER
TROPICAL CYCLONES WHICH MADE LANDFALL (2024: BERYL, FRANCINE,
HELENE, AND MILTON) WHILE DROPPING AN OLDER ONE (2019: DORIAN).
E. IMPROVE METHOD TO DETECT WHEN TO STOP RUNNING A STORM.
PREVIOUSLY, IT DID NOT PROPERLY CONSIDER VERY LARGE TROPICAL
CYCLONES (TC) THAT WERE LARGER THAN A SLOSH BASIN, WHICH
RESULTED IN LARGE TC PERTURBATIONS BEING PREMATURELY STOPPED.
F. OTHER VARIOUS CODE OPTIMIZATIONS.
DISSEMINATION CHANGES:
NCEP NOMADS WEB SERVICES:
THERE WILL BE NO CHANGE TO THE DIRECTORY STRUCTURE ON NOMADS.
ALL DATA FROM CONUS, PUERTO RICO / U.S. VIRGIN ISLANDS, AND
HAWAII PRODUCTS WILL BE PRESENT IN THE SAME DIRECTORY:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/PSURGE/PROD/
WE ARE INTRODUCING SHEF PRODUCTS FOR CONUS AND PUERTO RICO AND
US VIRGIN ISLANDS, WHICH WILL HAVE SUFFIXES OF '.SHEF'. FOLLOW
ON IMPLEMENTATIONS WILL PURSUE SHEF PRODUCTS FOR OTHER REGIONS.
EXAMPLES OF THE NEW NOMADS SHEF FILENAMES:
BB##YYYY_YYYYMMDD_CONUS_EEE.SHEF
BB##YYYY_YYYYMMDD_PUERTORI_EEE.SHEF
(WHERE BB## IS THE STORM NUMBER,
YYYY IS THE YEAR,
YYYYMMDDHH IS THE DATE AND HOUR, AND
EE IS EXCEEDANCE ABOVE MEAN-LOWER-LOW-WATER (10, 50,
90))
WE ARE DISCONTINUING THE 0-80 HOUR MESSAGE IN THE CUMULATIVE
ABOVE DATUM (CUM_DAT) PRODUCTS IN FAVOR OF THE ALREADY EXISTING
0-102 HOUR MESSAGE. THIS ONLY IMPACTS THE CONUS REGION AS WE
DIDN'T CREATE 0-80 HOUR MESSAGES FOR THE PUERTO RICO AND US
VIRGIN ISLANDS REGION, NOR FOR THE HAWAIIAN REGION. THE GRIB
FILES WILL CONTINUE TO EXIST, BUT WILL HAVE 1 MESSAGE INSTEAD OF
2.
EXAMPLES OF THE IMPACTED NOMADS GRIB FILENAMES:
PSURGE.TYYYYMMDDHHZ.BB##YYYY_EEE_CUM_DAT.H102.CONUS_625M.GRIB2
PSURGE.TYYYYMMDDHHZ.BB##YYYY_GTF_CUM_DAT.H102.CONUS_625M.GRIB2
(WHERE YYYYMMDDHH IS THE DATE AND HOUR,
BB## IS THE STORM NUMBER,
YYYY IS THE YEAR,
EE IS THE EXCEEDANCE ABOVE DATUM (NAVD-88) (10, 20,
30,
40, 50, 60, 70, 80, 90), AND
F IS THE FEET ABOVE DATUM (NAVD-88) (2, 3, ..., 20))
NOAAPORT/SBN:
THE PRODUCTS ARE AVAILABLE OVER THE SBN AND NOAAPORT IN GRIB2
FORMAT. A COMPLETE LIST OF WMO HEADER IDS FOR THE PRODUCTS CAN
BE FOUND ONLINE AT THE TOP OF THE METEOROLOGICAL DEVELOPMENT
LABORATORY'S STORM SURGE TECHNICAL NOTICES HERE:
HTTPS://VLAB.NOAA.GOV/WEB/MDL/TECHNICAL-NOTICES-STORM-SURGE
OR MORE DIRECTLY AT:
HTTPS://VLAB.NOAA.GOV/DOCUMENTS/6609493/7858383/P-SURGE-V3.2-
HEADERS.PDF/DFF16835-E0CD-D532-D434-BB46D556A7CD?T=1772028616342
NOTE, DUE TO BANDWIDTH LIMITATIONS, SOME OF THE PRODUCTS ON
NOMADS ARE NOT DISSEMINATED OVER THE SBN. THE SBN WILL CONTAIN
THE FOLLOWING:
6-HOURLY CUMULATIVE AND INCREMENTAL PRODUCTS TO 102 HOURS:
A. (10, 20, 30, 40, 50, 90)% EXCEEDANCE ABOVE GROUND LEVEL
B. PROBABILITY OF > (1, 2, 3, ..., 10) FEET ABOVE GROUND
LEVEL
102-HOURLY CUMULATIVE PRODUCTS:
A. (10, 20, 30, 40, 50, 90)% EXCEEDANCE ABOVE DATUM
B. PROBABILITY OF > (2, 3, 4, ..., 15) FEET ABOVE DATUM
SEVERAL CANNED TEST RUNS WILL BE AVAILABLE FOR TESTING. THE
DATA WILL BE HOSTED ON THE NCEP HTTPS SITES AT THE FOLLOWING
URLS WHEN THEY ARE AVAILABLE, ALTHOUGH THEY MAY NOT BE PRESENT
FOR THE ENTIRE 30-DAY PERIOD:
HTTPS://NOMADS.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/PSURGE/PARA/
NCEP ENCOURAGES USERS TO ENSURE THEIR DECODERS ARE FLEXIBLE AND
ARE ABLE TO ADEQUATELY HANDLE CHANGES IN CONTENT ORDER, CHANGES
IN THE SCALING FACTOR COMPONENT WITHIN THE PRODUCT DEFINITION
SECTION (PDS) OF THE GRIB FILES, AND ANY VOLUME CHANGES THAT MAY
BE FORTHCOMING. THESE ELEMENTS MAY CHANGE WITH FUTURE NCEP
MODEL IMPLEMENTATIONS.NCEP WILL MAKE EVERY ATTEMPT TO ALERT
USERS TO THESE CHANGES PRIOR TO ANY IMPLEMENTATIONS.
ANY QUESTIONS, COMMENTS OR REQUESTS REGARDING THIS
IMPLEMENTATION SHOULD BE DIRECTED TO THE CONTACTS BELOW. WE
WILL REVIEW ANY FEEDBACK AND DECIDE WHETHER TO PROCEED.
FOR QUESTIONS REGARDING THE SCIENCE CHANGES, PLEASE CONTACT
ARTHUR TAYLOR
METEOROLOGICAL DEVELOPMENT LABORATORY
ARTHUR.TAYLOR@NOAA.GOV
FOR QUESTIONS ABOUT THE DATAFLOW ASPECTS, 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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