577
FXHW01 KWNH 210800
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EST SUN DEC 21 2025
VALID 00Z MON 22 DEC 2025 - 00Z MON 29 DEC 2025
AN UPPER-LEVEL RIDGE IS FORECAST TO REMAIN THE DOMINANT FEATURE
OVER THE STATE THROUGH MUCH OF THE WEEK BEFORE SHIFTING EASTWARD
AS THE WEEKEND APPROACHES. AT THE SURFACE, STRONG HIGH PRESSURE
BUILDING WELL NORTH OF THE ISLANDS WILL MAINTAIN NORTHEASTERLY TO
EASTERLY TRADE WINDS THROUGH AT LEAST MIDWEEK. BY THE LATTER HALF
OF THE WEEK, THE SURFACE HIGH IS EXPECTED TO SHIFT FARTHER EAST,
ALLOWING THE LOCAL PRESSURE GRADIENT TO RELAX AND LOW-LEVEL WINDS
TO VEER TOWARD A MORE SOUTHEASTERLY DIRECTION.
PRECIPITABLE WATER (PW) ANOMALIES ARE EXPECTED TO REMAIN POSITIVE
THROUGH THE EARLY PART OF THE WEEK AS THE ROBUST TRADE WIND FLOW
DRAWS ADDITIONAL MOISTURE INTO THE REGION. THIS WILL LIKELY FOCUS
CLOUDS AND SHOWERS ALONG THE WINDWARD SLOPES AND THE MAUKA AREAS.
A DRYING TREND IS FORECAST BY MIDWEEK AS A MORE STABLE AIRMASS
SPREADS ACROSS THE ISLANDS. WHILE A FRONTAL BOUNDARY WILL
GRADUALLY APPROACH THE STATE FROM THE WEST LATE IN THE WEEK,
GLOBAL MODELS ARE IN REASONABLE AGREEMENT THAT THIS FEATURE WILL
REMAIN WEST OF THE ISLANDS THROUGH THE END OF THE PERIOD.
PEREIRA
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