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FXHW01 KWNH 200745
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 AM EST SAT DEC 20 2025
VALID 00Z SUN 21 DEC 2025 - 00Z SUN 28 DEC 2025
AN UPPER-LEVEL RIDGE IS FORECAST TO BUILD OVER THE ISLANDS BY THE
START OF THE PERIOD AND REMAIN IN PLACE THROUGH MID-WEEK. A
STABLE PATTERN, SUPPORTED BY SURFACE HIGH PRESSURE BUILDING NORTH
OF THE ISLANDS, WILL MAINTAIN EASTERLY TRADES ACROSS THE ISLAND
CHAIN THROUGH AT LEAST WEDNESDAY. GLOBAL MODELS INDICATE POSITIVE
PRECIPITABLE WATER ANOMALIES WILL PERSIST THROUGH MID-WEEK,
SUPPORTING PASSING SHOWERS ALONG THE WINDWARD SLOPES. BY LATE IN
THE WEEK, THE UPPER RIDGE AND SURFACE HIGH ARE EXPECTED TO SHIFT
EAST, ALLOWING THE LOCAL PRESSURE GRADIENT TO RELAX AND LOW-LEVEL
WINDS TO VEER TOWARD A MORE SOUTHEASTERLY DIRECTION. DRIER AIR IS
FORECAST TO FILTER IN FROM THE EAST DURING THE LATTER HALF OF THE
PERIOD. THERE IS SOME MINOR MODEL DIVERGENCE REGARDING THE ARRIVAL
OF THIS DRIER AIRMASS, AS THE GFS REMAINS SLOWER TO PROGRESS THE
DRY AIR COMPARED TO THE MORE PROGRESSIVE ECMWF AND CANADIAN
SOLUTIONS.
PEREIRA
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