664
FXHW01 KWNH 220810
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 AM EST MON DEC 22 2025
VALID 00Z TUE 23 DEC 2025 - 00Z TUE 30 DEC 2025
AN UPPER-LEVEL RIDGE IS FORECAST TO REMAIN THE DOMINANT SYNOPTIC
FEATURE OVER THE ISLAND CHAIN THROUGH MUCH OF THE WEEK BEFORE
SHIFTING EASTWARD BY THE WEEKEND. AT THE SURFACE, STRONG RIDGING
BUILDING NORTH OF THE STATE WILL SUPPORT A STABLE PATTERN OF FRESH
NORTHEASTERLY TO EASTERLY TRADE WINDS THROUGH MIDWEEK. GLOBAL
MODELS AND HREF GUIDANCE INDICATE THAT POSITIVE PRECIPITABLE WATER
(PW) ANOMALIES WILL PERSIST EARLY ON ACROSS THE REGION, WITH
INCREASING EASTERLY FLOW ON TUESDAY SET TO BRING A SURGE OF DEEPER
MOISTURE TO THE ISLANDS. THIS UPTICK IN MOISTURE MAY RESULT IN
MORE WIDESPREAD SHOWERS, POTENTIALLY REACHING CLIMATOLOGICALLY
DRIER LEEWARD AREAS. HREF PROBABILITIES SUGGEST 24-HOUR
ACCUMULATIONS EXCEEDING ONE INCH ARE POSSIBLE IN SOME LOCATIONS.
BY LATE IN THE WEEK AND INTO THE WEEKEND, THE SURFACE HIGH IS
FORECAST TO SHIFT FARTHER EAST, ALLOWING THE LOCAL PRESSURE
GRADIENT TO RELAX AND LOW-LEVEL WINDS TO VEER TOWARD A MORE
SOUTHEASTERLY DIRECTION. DRIER AIR IS EXPECTED SPREAD ACROSS THE
ISLAND CHAIN STARTING WEDNESDAY, LIKELY RE-EASTABLISHING A MORE
STABLE TRADE WIND INVERSION. WHILE A COLD FRONT WILL GRADUALLY
APPROACH FROM THE WEST DURING THE LATTER HALF OF THE PERIOD,
CURRENT MODEL AGREEMENT SUGGESTS THIS BOUNDARY WILL REMAIN WEST OF
THE ISLANDS INTO THE EARLY PART OF NEXT WEEK.
PEREIRA
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