443
FXHW01 KWNH 200736
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 AM EDT MON APR 20 2026
VALID 00Z TUE 21 APR 2026 - 00Z TUE 28 APR 2026
OVERALL, THERE IS ABOVE-AVERAGE AGREEMENT AMONG THE GLOBAL
DETERMINISTIC AND ENSEMBLE GUIDANCE THROUGH THE FIRST HALF OF THE
PERIOD, WITH THE FORECAST SPREAD INCREASING SLIGHTLY BY NEXT
WEEKEND. ALOFT, THE GFS AND ECMWF IN PARTICULAR ARE IN SOLID
AGREEMENT REGARDING THE EASTWARD DEPARTURE OF THE UPPER-LEVEL
TROUGH ON TUESDAY. AT THE SURFACE, BY WEDNESDAY NIGHT THE
GUIDANCE CONTINUES TO WASH OUT THE WEAK SURFACE TROUGH INTERACTING
WITH THE WESTERN ISLANDS (KAUAI AND OAHU). WITH THE DEPARTURE OF
THE UPPER-LEVEL TROUGH ON TUESDAY, THE THREAT OF ISOLATED SHOWERS
AND THUNDERSTORMS, WHICH PRIMARILY IMPACTED THE WESTERN END OF THE
STATE AND THE INTERIOR BIG ISLAND OVER THE WEEKEND, WILL DIMINISH
SIGNIFICANTLY.
BY WEDNESDAY, WITH THE DIFFUSE SURFACE TROUGH WASHING OUT THE
TRADE WINDS, A DIURNAL LAND-SEA BREEZE CONVECTIVE REGIME WILL
DOMINATE. OVERALL MOISTURE AVAILABILITY APPEARS MODEST, SO
WIDESPREAD, HEAVY RAINFALL IS NOT EXPECTED. INSTEAD, EXPECT MAINLY
ISOLATED AFTERNOON SHOWERS ACROSS ISLAND INTERIORS AND LEEWARD
SLOPES.
FROM THURSDAY THROUGH MONDAY, AS THE SURFACE HIGH BUILDS NORTH OF
THE STATE, MODERATE EASTERLY TRADES WILL RETURN. THIS WILL SHIFT
THE PRECIPITATION FOCUS BACK TO A CLASSIC, STABLE TRADE WIND
PATTERN, WITH SHORT-DURATION SHOWERS FAVORING WINDWARD SLOPES.
HURLEY
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