224
FXHW01 KWNH 180814
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
414 AM EDT SUN OCT 18 2026
VALID 00Z MON 19 OCT 2026 - 00Z MON 26 OCT 2026
THE GUIDANCE AGREES ON BRISK TRADE WINDS IN ASSOCIATION WITH A
HIGH PRESSURE SYSTEM THAT BECOMES INCREASINGLY WARM CORE, BUILDING
TO THE NORTH OF THE ISLANDS THROUGH MONDAY. DISTURBANCES IN THE
EASTERLIES BRING SLIGHTLY ENHANCED MOISTURE (PRECIPITABLE WATER
VALUES OF 1.25-1.5") DURING THIS TIME FRAME WHICH SHOULD LEAD TO
A RAINFALL UPTICK IN THE MAUKA SHOWER REGIME. MEANWHILE, DIRECTLY
OVER HAWAI'I, A STRONGLY POSITIVELY TILTED UPPER TROUGH REMAINS
ACROSS THE STATE, WITH THE GUIDANCE GENERALLY AGREEING ON A MID-
LEVEL LOW FORMING MIDWEEK JUST NORTH OF THE MAIN ISLANDS.
LATE NEXT WEEK INTO NEXT WEEKEND, THE GUIDANCE IS MOVING A NEW
COLD LOW TO THE NORTH OF HAWAI'I WHICH LIFTS THE MID- LEVEL LOW
PREVIOUSLY NORTH OF HAWAI'I NORTHEAST (A COMPROMISE OF THE 00Z
ECMWF/GFS SPLITS THE DIFFERENCE SEEN IN THE GUIDANCE WITH THIS
SECOND MID- TO UPPER-LEVEL FEATURE). IT DRAMATICALLY WEAKENS THE
TRADES AND STARTS TO SHIFT/BUCKLE THE ITCZ/MONSOON TROUGH TO THE
SOUTHEAST OF THE STATE. THERE REMAINS A HEAVY RAINFALL SIGNAL LATE
NEXT WEEK INTO NEXT WEEKEND EAST OF HAWAI'I NEAR THIS WAVE IN THE
ITCZ/MONSOON TROUGH, THOUGH IT HAS WEAKENED A BIT FROM THE
GUIDANCE SEEN THIS TIME YESTERDAY.
ROTH
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