015
FXHW01 KWNH 170818
PMDHI
HAWAII EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
418 AM EDT THU SEP 17 2026
VALID 00Z FRI 18 SEP 2026 - 00Z FRI 25 SEP 2026
...PERIODS OF FLASH FLOODING/EXCESSIVE RAINFALL WITH THE REMAINS
OF NORBERT AND T.D. 15-E...
OVERALL, THE GUIDANCE SHOWS REASONABLE AGREEMENT OVER THE NEXT
WEEK. PRECIPITABLE WATER VALUES ARE ABOVE AVERAGE THROUGH THE
NEXT WEEK, WHICH SHOULD LEAD TO HEAVIER THAN AVERAGE RAINFALL
THROUGH THE PERIOD. NORBERT'S REMNANTS ENGULF THE STATE
TODAY/THURSDAY, KEEPING WINDS BRISK WITH MODERATE TO HEAVY SHOWERS
OVERTAKING THE MAIN HAWAIIAN ISLANDS INTO FRIDAY. EXCESSIVE
RAINFALL RATES ARE POSSIBLE ALONG MANY OF THE WINDWARD SLOPES OF
THE ISLANDS WITH FLOODING IMPACTS POSSIBLE AS PRECIPITABLE WATER
VALUES REACH 2-2.2" IN THE 00Z GFS/ECMWF GUIDANCE. BY THE WEEKEND,
NORBERT'S LOW- LEVEL SWIRL WILL EXIT TO THE WEST BUT ABOVE
AVERAGE MOISTURE REMAINS, LEADING TO WINDWARD/MAUKA SHOWERS WITH
HEAVIER RAINFALL THAN USUAL.
RIDGING ACROSS THE NORTH-CENTRAL PACIFIC GETS SMALLER IN SCALE AS
AN UPPER LEVEL TROUGH DIGS TO THE WEST OF THE INTERNATIONAL
DATELINE AND UPPER LEVEL TROUGHING STRENGTHENS/AMPLIFIES ACROSS
THE NORTHEAST PACIFIC, PARTICULARLY FROM MONDAY ONWARD. TO SOME
DEGREE, THE SURFACE RIDGE RESPONDS, AND THERE SHOULD BE AT LEAST
MODEST WEAKENING OF THE TRADE WINDS AFTER NORBERT PASSES BY. THE
REMAINS OF T.D. 15-E MOVE FAIRLY CLOSE TO THE SOUTH FROM LATE
TUESDAY THROUGH THURSDAY, INCREASING THE INTENSITY OF RAINFALL --
EXCESSIVE RAINFALL/FLASH FLOODING IS AGAIN POSSIBLE AND COULD BE
MORE EXPANSIVE/INTENSE. PRECIPITABLE WATER VALUES COULD BE HIGHER
THAN WITH NORBERT -- THE 00Z GFS/ECWMF ADVERTISE PRECIPITABLE
WATER VALUES REACHING 2.4-2.6".
ROTH
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