844
FXHW01 KWNH 170730
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 AM EDT SAT OCT 17 2026
VALID 00Z SUN 18 OCT 2026 - 00Z SUN 25 OCT 2026
THE GUIDANCE AGREES ON BRISK TRADE WINDS A HIGH PRESSURE SYSTEM
THAT BECOMES INCREASINGLY WARM CORE BUILDS TO THE NORTH OF THE
ISLANDS THROUGH MONDAY. 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 OVER THE MAIN ISLANDS. LATE NEXT WEEK INTO NEXT WEEKEND,
THE GUIDANCE IS INCREASINGLY FORMING A NEW COLD LOW WHICH DROPS
HAWAI'I WHICH LIFTS THE MID-LEVEL LOW PREVIOUSLY NORTH OF HAWAI'I
NORTHEAST. IT WILL ALSO DRAMATICALLY WEAKEN THE TRADES AND STARTS
TO SHIFT/BUCKLE THE ITCZ/MONSOON TROUGH TO THE SOUTHEAST OF THE
STATE.
THROUGH MONDAY, DISTURBANCES IN THE EASTERLIES BRING ENHANCED
MOISTURE (PRECIPITABLE WATER VALUES OF 1.5"+) WHICH SHOULD LEAD TO
A RAINFALL UPTICK IN THE MAUKA SHOWER REGIME DURING THOSE
PERIODS. NOW THAT THE GUIDANCE IS MORE AGREEABLE ON A NEW COLD LOW
DROPPING TOWARDS HAWAI'I, THE HEAVY RAINFALL SIGNAL LATE NEXT
WEEK INTO NEXT WEEKEND HAS SHIFTED EAST OF HAWAI'I NEAR THE
FORECAST BUCKLE/WAVE IN THE ITCZ/MONSOON TROUGH. TIME WILL TELL AS
TO WHETHER THIS GUIDANCE SHIFT PERSISTS AS WE GET CLOSER TO LATE
NEXT WEEK.
ROTH
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