884
FXHW01 KWNH 100703
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 AM EDT TUE MAR 10 2026
VALID 00Z WED 11 MAR 2026 - 00Z WED 18 MAR 2026
...PROLONGED AND POWERFUL KONA STORM TO BRING NUMEROUS IMPACTS
ACROSS HAWAII THIS WEEK INTO EARLY NEXT WEEK...
A HIGH-IMPACT AND POTENTIALLY LIFE-THREATENING WEATHER PATTERN
WILL UNFOLD ACROSS HAWAII THIS WEEK, AS A POWERFUL AND SLOW-MOVING
KONA LOW DEVELOPS NORTHWEST OF THE STATE. THIS SYSTEM IS FORECAST
TO BRING A PROLONGED PERIOD OF TORRENTIAL RAINFALL, AREAS OF FLASH
FLOODING, DAMAGING "KONA" WINDS, AND POTENTIALLY SEVERE
THUNDERSTORMS. GLOBAL GUIDANCE, PARTICULARLY THE ECMWF AND GFS,
CONTINUE TO SHOW GOOD CONSENSUS ON THE EVOLUTION OF THIS SYSTEM,
WITH THE PRIMARY MODEL DIFFERENCE BEING THE EXTENT OF THE EASTWARD
PROGRESSION OF THE ASSOCIATED SURFACE FRONT AND MOISTURE PLUME.
THE COMBINATION OF A DEEP, NEGATIVELY TILTED UPPER-LEVEL TROUGH
AND A PLUME OF DEEP TROPICAL MOISTURE WILL RESULT IN STATEWIDE
IMPACTS BEGINNING TUESDAY ACROSS THE WESTERN ISLANDS, SPREADING
EASTWARD AND PERSISTING THROUGH THE UPCOMING WEEKEND AND INTO
EARLY NEXT WEEK. TROPICAL MOISTURE (PWAT VALUES 1.75-2.00" WILL
SURGE NORTHWARD ACROSS THE WESTERN ISLANDS STARTING TUESDAY. KAUAI
WILL EXPERIENCE THE INITIAL ARRIVAL OF HEAVY RAIN AND EMBEDDED
THUNDERSTORMS, WITH THE ACTIVITY SPREADING EASTWARD TO OAHU AND
MAUI BY WEDNESDAY. FRIDAY INTO SATURDAY, PWAT VALUES PEAK ABOVE
2.0", WITH THE MOISTURE PLUME/MAXIMUM PWAT AXIS SHIFTING ACROSS
THE CENTRAL AND EASTERN ISLANDS ON SATURDAY, THEN LINGERING ALONG
THE BIG ISLAND SUNDAY INTO EARLY NEXT WEEK.
BY THE WEEKEND, THE CONCERN WILL BE WITH THE LIKELY ADDITIONAL
HEAVY RAINFALL OVERTOP ALREADY SATURATED SOILS, AND THEREFORE THE
RISK OF SIGNIFICANT FLASH FLOODING STATEWIDE. MEANWHILE THE
POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS PEAKS FRIDAY INTO
SATURDAY AS 0-6KM BULK SHEAR VALUES EXCEED 40KTS AND MUCAPES
AVERAGE 1500-2500 J/KG.
LASTLY, THE LATEST ECMWF ESAT OUTPUT CONTINUES TO INDICATE AN
EXTREME TO CLIMATOLOGICALLY RARE EVENT FOR THE MONTH OF MARCH IN
HAWAII. THIS AS PWAT VALUES ARE FORECAST TO EXCEED THE 99TH
PERCENTILE OF CLIMATOLOGY FOR MARCH ACROSS THE ENTIRE ISLAND
CHAIN. MOREOVER, THE 24-HR QPF RETURN PERIODS FOR SEVERAL ECMWF
ENSEMBLE MEMBERS SUGGEST A 10 TO 25 AVERAGE RECURRENCE INTERVAL OR
ARI (4-10% ANNUAL EXCEEDANCE PROBABILITY OR AEP) FOR TYPICALLY
LEEWARD LOCATIONS UNDER NORMAL TRADE WINDS. SHIFT-OF-TAILS OR SOT
VALUES OF 1 TO 2 INDICATE THAT SEVERAL ENSEMBLE MEMBERS ARE
FORECASTING AN 'EXTREME' EVENT WELL OUTSIDE THE MODEL'S HISTORICAL
DISTRIBUTION, WHICH PROVIDES HIGH CONFIDENCE IN THE POTENTIAL FOR
CONSIDERABLE FLASH FLOODING.
HURLEY
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