201
FXHW01 KWNH 130900
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EST SAT DEC 13 2025
VALID 00Z SUN 14 DEC 2025 - 00Z SUN 21 DEC 2025
...HEAVY RAINS FOR THE WESTERN HAWAIIAN ISLANDS POSSIBLY INTO
MUCH OF NEXT WEEK...
QUIET WEATHER IS EXPECTED SATURDAY WITH LIKELY SEA BREEZES ACROSS
THE BIG ISLAND AND SOUTHERLY FLOW FOR THE WESTERN HAWAIIAN
ISLANDS. THESE SOUTHERLY WINDS ARE IN RESPONSE TO A COLD FRONT
APPROACHING FROM THE NORTHWEST, WHICH IS FORECAST TO REACH KAUAI
SATURDAY NIGHT/EARLY SUNDAY WITH A NOTABLE MOISTURE PLUME ALONG
AND AHEAD OF IT. THIS FRONT IS SUPPORTED BY AN UPPER LOW TO THE
NORTHWEST, PLACING THE FAVORABLE RIGHT ENTRANCE REGION OF THE JET
ATOP THE WESTERN ISLANDS. THESE INGREDIENTS WILL ALLOW FOR
POTENTIALLY HEAVY RAINFALL OVER KAUAI/NI'IHAU, WITH NUMEROUS
SHOWERS REACHING OAHU AS WELL ON SUNDAY PER THE HREF. THE FRONT IS
LIKELY TO STALL INTO MONDAY FOR ADDITIONAL HEAVY RAINFALL.
FLOODING IS A CONCERN, AND A FLOOD WATCH IS IN EFFECT LATE
SATURDAY NIGHT INTO LATE MONDAY NIGHT.
THE UPPER AND SURFACE LOWS NORTHWEST OF HAWAII WILL BE SLOW TO
MOVE EAST INTO TUESDAY-WEDNESDAY. THE STALLING FRONT COULD LIFT
NORTHWEST A BIT IN RESPONSE TO A SECONDARY FRONT APPROACHING.
MEANWHILE, INSTABILITY IS LIKELY TO INCREASE AHEAD OF THESE
FRONTS, WITH SOMEWHAT UNUSUALLY HIGH VALUES FOR CAPE PER THE
EXTREME FORECAST INDEX. THUS HEAVY RAIN IN SHOWERS AND POSSIBLY
THUNDERSTORMS REMAINS LIKELY INTO MIDWEEK AND EVEN INTO LATE WEEK
AS THE (LIKELY COMBINED) FRONTAL SYSTEM CONTINUES TO STALL. THE
EXACT POSITION OF THIS FRONT DOES SHOW SOME MODEL SPREAD. THE 00Z
GFS TENDS TO KEEP THE FRONT AND MOISTURE PLUME JUST WEST OF THE
STATE, WHILE THE 00Z ECMWF IS GENERALLY BETWEEN KAUAI AND OAHU FOR
MULTIPLE DAYS. THIS POSITIONING WILL HAVE A NOTABLE IMPACT ON
PLACEMENT OF HEAVY QPF, SO WILL CONTINUE TO MONITOR.
TATE
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