344
FXHW01 KWNH 270923
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
523 AM EDT TUE OCT 27 2026
VALID 00Z WED 28 OCT 2026 - 00Z WED 04 NOV 2026
IMPACTFUL WEATHER WILL IMPACT PORTIONS OF THE STATE BY TUESDAY
WITH AREAS OF HEAVY RAINFALL AND FLASH FLOODING. A WEAK WAVE OF
LOW PRESSURE ALONG AN ELONGATED TROUGH AXIS WILL MOVE TOWARDS THE
STATE TUESDAY INTO THURSDAY, BRINGING AN INCREASE IN FORCING AND
SOUTHWESTERLY LOW LEVEL WINDS AND MOISTURE TRANSPORT.
THERE ARE SEVERAL FAVORABLE INGREDIENTS FOR HEAVY RAINFALL WITH
THIS SYSTEM. SYNOPTIC FORCING WILL BE STRONG WITH FAVORABLE RIGHT
ENTRANCE REGION UPPER JET DYNAMICS. AN AXIS OF PWS AROUND 2.5"
WILL MOVE TOWARDS THE STATE, VALUES THAT ARE NEAR RECORD VALUES
FOR THE TIME OF YEAR. UP TO AROUND 1000 J/KG OF CAPE IS FORECAST
BY LATER TUESDAY INTO THURSDAY, WHICH GIVEN THE IMPRESSIVE
DYNAMICS AND STRONG LOW LEVEL CONVERGENCE, IS PLENTY TO SUPPORT
THUNDERSTORM DEVELOPMENT. SOME LATITUDINAL ADJUSTMENT OF THE MAX
RAINFALL AXIS IS POSSIBLE, BUT THE BEST MODEL CLUSTERING SUPPORTS
OAHU TO MAUI HAVING THE MOST CONCENTRATED CONVECTIVE THREAT.
PERIODS OF HIGH CONVECTIVE RAINFALL RATES ARE LIKELY, WITH AREAS
OF SIGNIFICANT FLASH FLOODING POSSIBLE.
THE MOST SIGNIFICANT AND WIDESPREAD HEAVY RAINFALL THREAT SHOULD
BE THROUGH EARLY THURSDAY. BY LATER THURSDAY FORCING WEAKENS AND
THE PLUME OF HIGHEST MOISTURE MOVES OFF TO THE EAST. HOWEVER, THE
TROUGH AXIS WILL REMAIN NEARBY AND PWS WILL STILL REMAIN ABOVE
AVERAGE INTO THE WEEKEND. MORE UNCERTAINTY ON THE DETAILS BY THIS
TIME, BUT IT LOOKS MORE LIKELY THAT THE BEST FOCUS FOR AREAS OF
HEAVIER RAINFALL BY LATE WEEK INTO THE WEEKEND WILL FOCUS ACROSS
THE NORMALLY FAVORED WINDWARD AREAS OF MAUI AND THE BIG ISLAND.
A FRONT MOVING THROUGH FROM THE NORTH SHOULD BEING DRIER AIR AND
A DECREASE IN THE RAINFALL THREAT BY NEXT WEEK. HOWEVER QUITE A
BIT OF MODEL SPREAD ON THE TIMING OF THESE IMPROVING CONDITIONS.
THE GFS IS QUICKEST, SUGGESTING IMPROVING CONDITIONS AS EARLY AS
FRIDAY, WITH THE AIFS KEEPING ELEVATED MOISTURE AND HIGHER RAIN
CHANCES THROUGH SUNDAY.
CHENARD
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