260
FXHW01 KWNH 090719
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
319 AM EDT MON MAR 9 2026
VALID 00Z TUE 10 MAR 2026 - 00Z TUE 17 MAR 2026
...PROLONGED AND POWERFUL KONA STORM TO BRING NUMEROUS IMPACTS
ACROSS HAWAII THIS WEEK INTO NEXT WEEKEND...
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 WITH LARGE HAIL. 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.
IN TERMS OF THE GUIDANCE, THE GLOBAL MODELS (GFS/ECMWF/CMC) AND
THEIR RESPECTIVE ENSEMBLES REMAIN IN REMARKABLY GOOD AGREEMENT
REGARDING THE LARGE-SCALE EVOLUTION OF THIS EVENT. MODELS CONTINUE
TO HIGHLIGHT A ~150KT UPPER LEVEL JET STREAK DIGGING INTO THE
WESTERN FLANK OF THE TROUGH, POSITIONING THE ISLANDS IN THE
FAVORABLE LEFT-EXIT REGION FOR A LENGTHY TIME, RESULTING IN
PERSISTENT UPPER LEVEL DIFLUENCE AND ROBUST DEEP-LAYER ASCENT.
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. SEVERE THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY WITH
DEEP-LAYER CAPES AVERAGING 1200-1700 J/KG AND COOLING 500 MB TEMPS
(-10C) ENHANCING THE INSTABILITY. FLASH FLOODING IS A PRIMARY
CONCERN AS RAINFALL RATES MAY EXCEED 2-3" PER HOUR WITHIN THE
STRONGEST BANDS.
DURING DAYS 4-7 (FRIDAY THROUGH MONDAY), THE CONCERN WILL BE WITH
THE LIKELY ADDITIONAL HEAVY RAINFALL OVERTOP ALREADY SATURATED
SOILS. WHILE THE GUIDANCE SUGGESTS A POTENTIAL BRIEF LULL ON
THURSDAY, A SECOND, MORE VIGOROUS SHORTWAVE IS EXPECTED BY FRIDAY.
FRIDAY INTO SATURDAY ALSO APPEARS TO BE THE WINDOW WITH THE
GREATEST SEVERE WEATHER RISK, WITH POTENTIALLY DAMAGING SOUTHERLY
WINDS (50+ MPH GUSTS) ON NORTHERN AND EASTERN SLOPES.
LASTLY, THE LATEST ECMWF ESAT OUTPUT CONTINUES TO INDICATE AN
EXTREME TO CLIMATOLOGICALLY RARE EVENT FOR THE MONTH OF MARCH IN
HAWAII. QPF INDEX VALUES REMAIN ABOVE 0.90 INTO NEXT MONDAY, WITH
SHIFT OF TAILS (SOT) OCCASIONALLY REACHING 2+. THESE SOT VALUES
SUGGEST THAT THE HIGH-END POTENTIAL OF THIS KONA STORM IS
SIGNIFICANTLY OUTSIDE THE REALM OF "NORMAL" WET SEASON WEATHER.
HURLEY
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