242
FXHW60 PHFO 151306
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
306 AM HST MON SEP 15 2025
SYNOPSIS
HIGH PRESSURE RIDGING NORTH OF THE HAWAIIAN ISLANDS AND A WEAK
LOW PROPAGATING WESTWARD SOUTH OF THE ISLANDS WILL MAINTAIN STABLE
WEATHER CONDITIONS UNDER MODERATE TO LOCALLY BREEZY TRADES
THROUGHOUT THE DAY. A SHIFT IN WEATHER BEGINS TUESDAY, AS A BRIEF
UPTICK IN SHOWER ACTIVITY IS EXPECTED AS A BATCH OF DEEPER
MOISTURE MEANDERS INTO THE VICINITY OF THE STATE. FOR THE LATTER
END OF THE WEEK THROUGH THE WEEKEND, EXPECT PERIODS OF SHOWERS
WITH INCREASED CLOUD COVERAGE ASSOCIATED WITH ANOTHER BATCH OF
DEEP MOISTURE.
DISCUSSION
BROAD AREA OF HIGH PRESSURE AND ASSOCIATED RIDGING REMAINS
QUASI-STATIONARY JUST NORTH OF THE HAWAIIAN ISLANDS AS A WEAK LOW
PRESSURE SYSTEM CONTINUES TO PROPAGATE WESTWARD SOUTH OF THE
STATE, PRODUCING A TIGHT PRESSURE GRADIENT RESPONSIBLE FOR
INCREASED WIND SPEEDS. STABLE CONDITIONS WILL MAINTAIN A
RELATIVELY DRY SUMMER WEATHER PATTERN WITH MODERATE TO LOCALLY
BREEZY TRADES THROUGH THE DAY TODAY, DECREASING SLIGHTLY
THROUGH EARLY WEDNESDAY.
AS THE WEEK PROGRESSES THEREAFTER, TRADES INCREASE SLIGHTLY, AS
WELL AS BRING AN UPTICK IN SHOWER ACTIVITY AND INCREASING CLOUD
COVERAGE AS A BATCH OF DEEPER MOISTURE MOVES INTO THE VICINITY OF
THE ISLANDS, PRIMARILY IMPACTING WINDWARD AND MAUKA AREAS,
HOWEVER, LEEWARD AREAS MAY SEE SOME OF THE STRONGER TRADE WIND
SHOWERS. THAT SAID, THESE SHOWERS WILL DISSIPATED AS QUICKLY AS
THEY ARRIVE AND OVERALL MOISTURE CONTENT WILL BE LIMITED.
LATEST DETERMINISTIC MODEL GUIDANCE SUGGESTS UNSETTLED WEATHER
CONDITIONS CONTINUE THURSDAY, PERSISTING THROUGH MUCH OF THE
WEEKEND. GUIDANCE DEPICTS A FRONTAL SYSTEM EXTENDING WELL NORTH
FROM THE GULF OF ALASKA AND EXTENDING SOUTHWARD SOUTH OF 40N. THIS
FRONT WILL PERPETUATE TRADES WITH DEEPER MOISTURE AHEAD OF THE
AFOREMENTIONED HIGH PRESSURING PINCHING OFF THE TAIL END, PIVOTING
THIS MOISTURE TOWARD THE VICINITY OF THE ISLANDS. THE EXCESS
DEEPER MOISTURE WILL COINCIDE WITH THE LATTER END OF THIS WEEK'S
PROGGED TEMPERATURE INVERSION LEVELS, SITUATED AROUND THE 7,000
FOOT ELEVATION LEVEL, SUPPORTIVE OF ISOLATED TO SCATTERED SHOWERS
THROUGHOUT THE DAY, AND SCATTERED TO NUMEROUS SHOWERS OVERNIGHT
THROUGH THE WEEKEND. WHILE THE INCREASE TRADE WIND SHOWERS WILL
HIGHER COVERAGE PREDOMINATELY ACROSS WINDWARD AND MAUKA AREAS, IT
CANNOT BE RULED OUT THAT LEEWARD AREAS MAY SEE BRIEF SPILLOVER.
AVIATION
MODERATE TO LOCALLY BREEZY TRADE WINDS WILL CONTINUE THROUGH THE
FORECAST PERIOD. LIMITED CLOUDS AND SHOWERS WILL FAVOR WINDWARD
AND MAUKA AREAS, WITH A SLIGHT UPTICK DURING THE OVERNIGHT HOURS.
CONDITIONS REMAIN PREDOMINATELY VFR, WITH BRIEF MVFR POSSIBLE
UNDER PASSING SHOWERS.
NO AIRMETS ARE IN EFFECT AND NONE ARE ANTICIPATED THROUGH THE
FORECAST PERIOD.
MARINE
MODERATE TO LOCALLY STRONG TRADES EXPECTED THROUGH THIS
AFTERNOON. AS SUCH A SMALL CRAFT ADVISORY (SCA) REMAINS IN EFFECT
FOR THE WINDIER CHANNELS AND WATERS AROUND MAUI AND THE BIG
ISLAND THROUGH 6PM TONIGHT. A HIGH TO THE NORTH WILL WEAKEN
SLIGHTLY ON TUESDAY ALLOWING TRADES TO EASE. WINDS SHOULD
RESTRENGTHEN BY MID- WEEK BRINGING BACK A SCA.
THE RECENT SMALL, MEDIUM PERIOD NORTH SWELL WILL SLOWLY DECLINE
TODAY. ANOTHER MEDIUM PERIOD NORTH SWELL IS EXPECTED TO ARRIVE
THURSDAY AND MAY CAUSE A SLIGHT BUMP IN SURF ALONG NORTH- FACING
SHORES.
A SMALL, MEDIUM- TO LONG-PERIOD SOUTH SWELL WILL KEEP SURF ALONG
SOUTH-FACING SHORES NEAR THE SEPTEMBER AVERAGES GRADUALLY
DECLINING TONIGHT THROUGH MID-WEEK. A COUPLE OF VERY SMALL
REINFORCEMENTS ARE EXPECTED THROUGHOUT THE WEEK, THOUGH SURF WILL
REMAIN SMALL. A SLIGHTLY LARGER, LONG-PERIOD SWELL IS FORECAST TO
ARRIVE IN THE ISLANDS FRIDAY NIGHT, BOOSTING SOUTH SHORE SURF NEXT
WEEKEND.
EAST FACING SHORES WILL SEE TYPICAL TRADE WIND GENERATED ENERGY
THROUGHOUT THE FORECAST PERIOD.
FIRE WEATHER
LOW HUMIDITY LEVELS PERSIST WITH SUSTAINED WINDS JUST UNDER
CRITICAL FIRE WEATHER THRESHOLDS FOR A FEW HOURS THIS AFTERNOON.
EXPECT DECREASING FIRE WEATHER CONCERNS BEGINNING TOMORROW ONWARD
THROUGH THE FORECAST PERIOD AS MINIMUM HUMIDITY LEVELS INCREASE.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...PIERCE
AVIATION...AHUE
MARINE...WALSH
FIRE WEATHER...PIERCE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page