857
FXHW01 KWNH 150747
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
347 AM EDT FRI MAY 15 2026
VALID 00Z SAT 16 MAY 2026 - 00Z SAT 23 MAY 2026
THE FORECAST PERIOD BEGINS WITH A TRANSITION IN THE MID/UPPER
LEVEL PATTERN AS A PERSISTENT ULL CURRENTLY NEAR THE ISLANDS
BEGINS TO LIFT AND WEAKEN. AT THE SURFACE, WEAK TROUGHING WILL
GRADUALLY GIVE WAY HIGH PRESSURE BUILDING BACK ACROSS THE ISLANDS
FROM THE NORTHEAST, WHICH WILL ALLOW SOUTHEASTERLY LOW-LEVEL FLOW
TO BACK TOWARD A MORE STABLE TRADE WIND REGIME. GIVEN THE
CONSISTENCY BETWEEN THE GEFS AND ECENS, A GENERAL MODEL BLEND IS
PREFERRED.
IN THE SHORT TERM (THROUGH MONDAY), AS THE MID/UPPER LOW DRIFTS
FARTHER AWAY FROM THE STATE, THE THREAT/COVERAGE OF CONVECTION
WILL DECREASE. WHILE THE INSTABILITY DECREASES OVER THE WEEKEND,
LOW-LEVEL MOISTURE WILL INCREASE FROM THE SOUTHEAST WITH PWAT
VALUES APPROACHING 2 INCHES BY LATE SATURDAY OVER THE WINDWARD BIG
ISLAND. THIS MOISTURE SURGE IS ASSOCIATED WITH A TROPICAL PLUME
RIDING THE PERIPHERY OF A STRENGTHENING RIDGE TO THE E-NE. PERIODS
OF HEAVY RAIN WILL BE POSSIBLE OVER THE WINDWARD AND SOUTHEAST BIG
ISLAND THIS WEEKEND, WITH SOME ENHANCED SHOWERS POSSIBLE
ELSEWHERE ACROSS THE STATE. THE FLOW WILL REMAIN LIGHT-MODERATE
SOUTHEASTERLY THROUGH SUNDAY, WHICH MAY LEAD TO SOME LEEWARD
ENHANCEMENT AND LOCALIZED SEA-BREEZE CONVECTION OVER THE SMALLER
ISLANDS WHERE TERRAIN-INDUCED CONVERGENCE IS MAXIMIZED. BY MONDAY,
THE MOISTURE PLUME BEGINS TO SHIFT WESTWARD, AND THE AIRMASS WILL
SLOWLY START TO STABILIZE AS THE ULL LOSES ITS INFLUENCE.
DURING THE MEDIUM RANGE (TUESDAY-SATURDAY), AS THE SURFACE HIGH TO
THE NORTH STRENGTHENS AND MIGRATES EASTWARD, THE PRESSURE GRADIENT
ACROSS THE CENTRAL PACIFIC WILL TIGHTEN. THIS WILL RESULT IN
MODERATE TO BREEZY EAST-NORTHEAST TRADES (15-25 MPH) TUESDAY AND
WEDNESDAY, AS PWAT VALUES DROP BACK TO 1.1-1.3 BY WED. THIS WILL
SHIFT THE RAINFALL DISTRIBUTION BACK TO THE CLASSIC WINDWARD AND
MAUKA FOCUS.
HURLEY
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