312
FXHW01 KWNH 120759
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
359 AM EDT THU MAR 12 2026
VALID 00Z FRI 13 MAR 2026 - 00Z FRI 20 MAR 2026
...PROLONGED AND POWERFUL KONA STORM TO BRING NUMEROUS IMPACTS
ACROSS HAWAII INTO EARLY NEXT WEEK...
A HIGH-IMPACT AND POTENTIALLY LIFE-THREATENING WEATHER PATTERN
WILL CONTINUE TO UNFOLD ACROSS HAWAII INTO EARLY NEXT WEEK. MODEL
GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE EVOLUTION OF THE
POWERFUL KONA STORM CENTERED A LITTLE OVER 1,000 MILES NORTHWEST
OF THE ISLAND CHAIN. AT THE SURFACE, A BROAD CYCLONIC CIRCULATION
WITH CENTRAL PRESSURES AT OR BELOW 990 MB WILL REMAIN POSITIONED
TO THE NORTHWEST OF THE ISLANDS THAT RESULTS IN A STRENGTHENING
WINDS. A POTENT, LARGE-SCALE TROUGH ALOFT WILL SHARPEN AND TAKE
ON A DISTINCT NEGATIVE TILT AS A 120-140 KT JET STREAK ON ITS
WESTERN FLANK DIGS SOUTHEAST. THIS CONFIGURATION WILL FOSTER A
PROLONGED PERIOD OF SIGNIFICANT LARGE-SCALE UPPER-LEVEL
DIVERGENCE AND THUS DEEP-LAYER ASCENT, WHICH WILL MAINTAIN
WIDESPREAD AREAS OF ORGANIZED CONVECTION WITH EMBEDDED
THUNDERSTORMS FOR SEVERAL DAYS.
PRECIPITABLE WATER VALUES PEAK BETWEEN 2.00-2.25"+ BY FRIDAY (3 TO
5 STANDARDIZED ANOMALIES GREATER THAN CLIMATOLOGY FOR MID-MARCH)
AND SATURDAY DURING THE PERIOD OF STRONGEST LEFT- EXIT REGION
UPPER FORCING. THE CONCERN WILL BE WITH THE LIKELY ADDITIONAL
HEAVY RAINFALL ON SOILS THAT ARE ALREADY NEAR SATURATIO, AND
THEREFORE THE RISK OF SIGNIFICANT FLASH FLOODING STATEWIDE. PER
BOTH THE GFS AND ECMWF, SATURDAY AND SUNDAY ARE STILL THE DAYS
THAT HAVE THE HIGHEST IVT VALUES/GREATEST IVT ANOMALIES WITH THE
VALUES GENERALLY PEAK AROUND 1000 KG/M-S.
THE LATEST ECMWF ESAT OUTPUT CONTINUES TO UNDERSCORE THE EXTREME
NATURE OF THIS EVENT, WITH EXTREME FORECAST INDEX (EFI) VALUES FOR
BOTH QPF AND PWAT REACHING 0.99 TO 1.00, OR THE MAXIMUM POSSIBLE
ANOMALY. MOREOVER, THE 24-HR QPF RETURN PERIODS FOR SEVERAL ECMWF
ENSEMBLE MEMBERS OVER THE WEEKEND, WHEN AVERAGE 24HR RAINFALL
PEAKS BETWEEN 3-6+ INCHES, SUGGEST A 25 TO 50 YEAR AVERAGE
RECURRENCE INTERVAL OR ARI. SOME IMPROVEMENT IS EXPECTED BY LATE
IN THE OUTLOOK PERIOD.
HURLEY/BANN
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