507
FXHW01 KWNH 200715
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 AM EDT TUE OCT 20 2026
VALID 00Z WED 21 OCT 2026 - 00Z WED 28 OCT 2026
HAWAII WILL GENERALLY BE TO THE SOUTH OF A SUBTROPICAL HIGH THAT
WILL BE SITUATED NEAR 35 DEGREES NORTH FOR THE MIDDLE OF THIS
WEEK, WITH STEADY ENE TRADE WINDS EXPECTED THROUGH WEDNESDAY. A
WELL DEFINED COL DEVELOPS WITHIN THIS SUBTROPICAL HIGH BY
WEDNESDAY NIGHT AND INTO THURSDAY AS A DEVELOPING LOW PRESSURE
SYSTEM OVER THE NORTH PACIFIC HEADS TOWARDS THE ESE, AND BRINGS A
FRONTAL BOUNDARY CLOSER TO THE NORTHWESTERN ISLANDS. THE TRADE
WINDS SHOULD DECREASE SOME AS THE PRESSURE GRADIENT WEAKENS IN
RESPONSE TO THE TROUGH NORTH OF THE STATE.
SIMILAR TO YESTERDAY, THE GUIDANCE STARTS TO DIVERGE ON HOW THIS
SYSTEM EVOLVES NORTH OF THE STATE TOWARDS SATURDAY. THE GEFS MEAN
BECOMES MORE PROGRESSIVE AND SLIGHTLY STRONGER, AND HAS THE LOW
NORTHEAST OF THE ECENS MEAN OVER THE WEEKEND. THE ECENS HAS
TRENDED A LITTLE STRONGER WITH THE LOW COMPARED TO YESTERDAY, AND
BECOMES STRONGER THAN THE GEFS BY NEXT MONDAY. THE DEEPEST TROPICAL
MOISTURE SHOULD STAY CONFINED WELL TO THE SOUTH, BUT SOME HIGHER
PWS AND INCREASED RAINFALL CHANCES ARRIVE BY SATURDAY AS THE
TROUGH ADVECTS SOME OF THIS MOISTURE TOWARDS THE NORTH, MAINLY
AFFECTING THE BIG ISLAND.
HAMRICK
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