544
FXHW01 KWNH 240845
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
445 AM EDT SAT OCT 24 2026
VALID 00Z SUN 25 OCT 2026 - 00Z SUN 01 NOV 2026
AN AREA OF LOW PRESSURE DROPPING SOUTH WELL TO THE NORTHEAST OF
THE ISLANDS WILL DISRUPT THE TRADE WINDS TO AN EXTENT OVER THE NEXT
COUPLE DAYS, ALTHOUGH STILL EXPECTING A STEADY NORTHEASTERLY
BREEZE ACROSS THE STATE. WITHIN THIS FLOW WE SHOULD SEE A
CONTINUATION OF PERIODIC SHOWERS ACROSS THE WINDWARD AREAS OF THE
BIG ISLAND AND MAUI.
MORE IMPACTFUL WEATHER IS LIKELY TO IMPACT PORTIONS OF THE STATE
BY TUESDAY INTO WEDNESDAY AS AN AREA OF LOW PRESSURE WELL WEST OF
THE ISLANDS MOVES EAST. REGARDLESS OF THE STATE OF THIS LOW, A
TROUGH AXIS EXTENDING EAST OF IT SHOULD HELP FOCUS AN INCREASING
RAINFALL THREAT. WHILE MODELS CONTINUE TO DISAGREE ON THE EXACT
STRENGTH/TRACK OF THIS LOW, THEY ALL GENERALLY DEPICT THIS TROUGH
AXIS AND PWS INCREASING TOWARDS 2.5", WITH A MID LEVEL TROUGH AND
UPPER LEVEL JET STREAK INCREASING FORCING ACROSS THE REGION. THERE
HAS BEEN ENOUGH MODEL AND RUN TO RUN AGREEMENT IN THIS OVERALL
SETUP TO INDICATE CONFIDENCE IS INCREASING IN A HEAVY RAINFALL
AND FLASH FLOOD RISK TUESDAY INTO WEDNESDAY. HOWEVER CONFIDENCE ON
THE DETAILS, SUCH AS EXACT TIMING/LOCATION/MAGNITUDE OF THE
THREAT REMAINS LOWER. THE 00Z GFS AND ECMWF ARE VERY AGGRESSIVE IN
BRINGING A SWATH OF HEAVY RAINFALL ACROSS THE CENTRAL ISLANDS,
AND WHILE THIS IS A PLAUSIBLE SCENARIO, THE ENSEMBLES AND PAST
DETERMINISTIC RUNS INDICATE THIS MAGNITUDE OF RAIN IS NOT LOCKED
IN. THUS WE WILL HAVE TO CONTINUE TO MONITOR TRENDS OVER THE
COMING DAYS.
THE PATTERN THURSDAY INTO SATURDAY IS UNCERTAIN. WHILE THE MOST
ORGANIZED HEAVY RAINFALL THREAT SHOULD DIMINISH BY THURSDAY,
THERE IS DISAGREEMENT IN THE GUIDANCE ON WHETHER ANOMALOUS
MOISTURE AND A WET PATTERN CONTINUES, OR IF SOME DRIER AIR
ADVECTS IN AND WE TRANSITION TO A MORE TYPICAL TRADE PATTERN.
CHENARD
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