697
FXHW60 PHFO 131331
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
331 AM HST SUN SEP 13 2026
SYNOPSIS
DRIER TRADE WINDS WILL PREVAIL EARLY THIS WEEK WITH LIGHT SHOWERS
ON THE WINDWARD SIDE OF THE ISLANDS. LOW LEVEL CONVERGENCE ALONG
A SURFACE TROUGH WILL BRING A MODEST INCREASE IN CLOUDS AND
SHOWERS LATE MONDAY INTO TUESDAY. MORE RAIN IS EXPECTED THROUGH
THE SECOND HALF OF THE WEEK AS REMNANTS OF TROPICAL STORM NORBERT
PASS BY.
DISCUSSION
EVENING SATELLITE IMAGERY SHOWS MOSTLY CLOUDY SKIES OVER THE BIG
ISLAND WITH MOSTLY CLEAR SKIES ELSEWHERE. LIGHT TRADE WINDS AND
ISOLATED LIGHT SHOWERS WILL CONTINUE TODAY.
A BROAD UPPER LEVEL LOW CURRENTLY NORTHEAST OF THE ISLANDS IS
FORECAST TO TRACK WESTWARD OVER THE NEXT SEVERAL DAYS. MOISTURE
ASSOCIATED WITH A DISTURBANCE CURRENTLY NEAR 13N 148W MAY BE
PULLED NORTHWARD INTO THE EASTERN HALF OF THE STATE AS BOTH IT AND
THE TROUGH MOVE WESTWARD. LOW LEVEL CONVERGENCE WILL BRING A
MODEST INCREASE IN CLOUDS AND SHOWERS LATE MONDAY INTO TUESDAY,
INITIALLY REACHING THE BIG ISLAND WITH SHOWERS BECOMING MORE
DIFFUSE AS THE TROUGH MOVES WEST.
TROPICAL STORM NORBERT IS CURRENTLY AROUND 1530 MILES EAST OF
HILO, MOVING WEST AT 12 MPH. THIS SYSTEM IS FORECAST TO CONTINUE
TO MOVE WESTWARD, WEAKENING TO A TROPICAL DEPRESSION BY TUESDAY
MORNING AND BECOMING POST-TROPICAL LATER THAT DAY. TRADE WINDS
WILL STRENGTHEN AS THE RESIDUAL TROUGH OF NORBERT PASSES THURSDAY
INTO FRIDAY. RAINFALL WILL ALSO INCREASE EAST TO WEST ACROSS THE
STATE FROM WEDNESDAY NIGHT THROUGH FRIDAY NIGHT. LARGE-SCALE
FORCING FROM AN UPPER TROUGH OVER THE REGION AND FORECAST
PRECIPITABLE WATER NEAR 2" WILL INCREASE THE FLOODING RISK,
ESPECIALLY FOR AREAS WHERE THE SOIL IS STILL SATURATED FROM RECENT
HEAVY RAINFALL.
AVIATION
SATELLITE IMAGERY INDICATES MOSTLY CLEAR CONDITIONS FOR HAWAII,
HOWEVER THERE ARE A FEW AREAS OF LOW CLOUDS WITH MVFR CONDITIONS
THIS MORNING. A LARGE UPPER LEVEL LOW WELL NORTHEAST OF THE
ISLANDS IS WEAKENING THE PRESSURE GRADIENT AND THEREFORE THE TRADE
WINDS NEAR HAWAII. THESE WEAK TO MODERATE TRADES WILL CONTINUE
THROUGH SUNDAY. WINDS MAY BECOME LIGHT ENOUGH WITHIN MORE WIND-
PROTECTED LEEWARD AREAS TO INITIATE LOCAL TOPOGRAPHICALLY- DRIVEN
BREEZES. THESE TRADES ARE ALSO RELATIVELY DRY, AND WILL LIMIT
SHOWER ACTIVITY.
MARINE
MODERATE TO LOCALLY FRESH TRADES WILL CONTINUE THROUGH THE WEEK
BEFORE GRADUALLY STRENGTHENING THROUGH THE LATTER HALF OF THE
WEEK. MOISTURE ASSOCIATED WITH A WEAK TROUGH MOVING IN ON THE
TRADE WIND FLOW MAY BRING A SLIGHT UPTICK IN SHOWER ACTIVITY TO
THE COASTAL WATERS TUESDAY INTO WEDNESDAY. WHILE THE CURRENT
FORECAST HAS TROPICAL STORM NORBERT DISSIPATING BEFORE IT NEARS
THE HAWAIIAN COASTAL WATERS FROM THE EAST, REMNANT MOISTURE FROM
THIS SYSTEM IS EXPECTED TO ARRIVE POTENTIALLY BY THURSDAY, LIKELY
BRINGING MORE SHOWERS.
SURF ALONG SOUTH-FACING SHORES WILL GRADUALLY DECLINE THROUGH MONDAY
AS THE SMALL, MEDIUM-PERIOD ENERGY SLOWLY FADES. A SERIES OF
LONG-PERIOD SWELLS ARE EXPECTED DURING THE SECOND HALF OF THE
WEEK. THE FIRST PULSE WILL GRADUALLY FILL IN TUESDAY INTO
WEDNESDAY OUT OF THE SOUTHWEST, FOLLOWED BY LARGER SOUTH-SOUTHWEST
SWELLS FRIDAY INTO THE WEEKEND. SURF COULD GET NEAR ADVISORY
THRESHOLDS OVER THE WEEKEND, BUT AT THIS TIME IT LOOKS LIKE IT
WOULD PEAK JUST BELOW ADVISORY THRESHOLDS.
A SMALL SHORT-PERIOD NORTHEAST SWELL FILLED IN OVERNIGHT AND WILL
PEAK TODAY AND FADE OUT ON MONDAY. SURF ALONG EAST-FACING SHORES
SHOULD SEE AN INCREASE DURING THE SECOND HALF OF THE WEEK AS THE
TRADES STRENGTHEN AND THE REMNANTS OF NORBERT MOVES THROUGH THE
ISLANDS. SOME SMALL ENERGY IS EXPECTED ALONG NORTHERN EXPOSURES
TODAY FROM THE NORTHEAST SWELL, BUT OTHERWISE FLAT TO TINY SURF
ALONG NORTH FACING SHORES IS EXPECTED THROUGH THE FORECAST
PERIOD.
FIRE WEATHER
FIRE WEATHER RISK WILL REMAIN LOW THE NEXT SEVERAL DAYS DUE LIGHT
TO MODERATE WINDS AND THE EFFECTS OF RECENT RAINFALL. INVERSION
HEIGHTS ARE EXPECTED TO REMAIN ELEVATED OR WEAK THROUGH MONDAY.
MOISTURE INCREASES FOR THE MIDDLE TO LATTER PART OF THE WEEK WITH
A BUMP IN THE TRADE WINDS AS REMNANTS FROM TROPICAL STORM NORBERT
POTENTIALLY APPROACH THE AREA.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...SS
AVIATION...PHILLIPS
MARINE...SHIGESATO
FIRE WEATHER...SS
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