945
FXHW60 PHFO 071339
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
339 AM HST SUN SEP 7 2025
SYNOPSIS
A BRIEF ENHANCEMENT IN SHOWER ACTIVITY THROUGH MONDAY MORNING IN
RESPONSE TO BOTH VICINITY TROUGHING NORTH OF THE STATE AND HIGHER
MOISTURE PASSING ACROSS THE ISLANDS FROM THE EAST. OVERALL, THE
REGION WILL REMAIN RELATIVELY DRY AND STABLE THE NEXT COUPLE OF
DAYS. CLOUDIER, WARM AND MUGGY ISLAND WEATHER IS FORECAST TUESDAY
AND WEDNESDAY UNDER WEAKENED TRADE FLOW. HURRICANE KIKO IS
APPROACHING HAWAII FROM THE SOUTHEAST. KIKO'S CURRENT FORECAST
TRACK REMAINS NORTH OF THE ISLANDS ACROSS THE FAR NORTHERN
OFFSHORE WATERS. WHILE CONFIDENCE IS LOW CONCERNING KIKO'S EARLY
TO MID WEEK IMPACTS, THERE IS A POSSIBLY OF HIGHER STATEWIDE
RAINFALL AND ELEVATED EAST-FACING SHORE SURF.
DISCUSSION
THIS MORNING'S SYNOPTIC PATTERN HAS A WEAK UPPER RIDGE AXIS JUST
SOUTH OF THE ISLANDS THAT IS BEING WORKED ON BY A SOUTHERN-
ADVANCING 579 DAM 500 MB DAM LOW LOCATED APPROXIMATELY 400 MILES
NORTH OF OAHU. THE ASSOCIATED TROUGH DRAPED ACROSS THE FAR
NORTHWEST OFFSHORE WATERS, ALONG WITH HURRICANE KIKO LOCATED ABOUT
700 MILES EAST SOUTHEAST OF HILO, HAWAII, HAVE DISRUPTED THE
DOWNSTREAM PRESSURE GRADIENT FROM A 1021 MB SURFACE HIGH CENTERED
1,100 MILES NORTH-NORTHEAST OF BIG ISLAND. THE RESULT WILL BE
LIGHTER TRADE WINDS WITHIN AN INCREASINGLY HUMID ISLAND
ENVIRONMENT. LIGHT BACKGROUND TRADE FLOW WILL OPEN THE DOOR FOR
MORE WIND-SHELTERED LOCALES TO EXPERIENCE LOCAL DIURNAL BREEZES.
A SURGE OF DEEPER, MORE MOIST-RICH AIR EMBEDDED WITHIN LIGHT
UPSTREAM TRADES AS NOTED ON THIS MORNING'S SHORTWAVE INFRARED
SATELLITE IMAGERY, IN TANDEM WITH THE WEAK INSTABILITY OF THE
TROUGH IN PROXIMITY OF THE NORTHWEST WATERS, IS PROVIDING ENOUGH
JUICE AND LIFT, RESPECTIVELY, TO GENERATE MORE AREAWIDE SHOWER
ACTIVITY THROUGH EARLY MONDAY. HIGHER RAIN AMOUNTS WILL BE
CONFINED TO NORTH AND EAST-FACING EXPOSURES AND AT HIGHER
ELEVATION.
CATEGORY THREE HURRICANE KIKO (EYE CENTERED 17N144W AT 3 AM HST)
IS MOVING WEST-NORTHWEST AT AROUND 15 MPH. KIKO IS FORECAST TO
CONTINUE TO WEAKEN AS IT APPROACHES THE HAWAIIAN ISLANDS FROM THE
SOUTHEAST. KIKO IS CURRENTLY FORECAST TO BE A HURRICANE WHEN IT
REACHES OUR FAR NORTHEAST OFFSHORE WATERS LATE MONDAY, WEAKENING
TO A TROPICAL STORM AS IT TRAVELS OVER OUR NORTHERN OFFSHORE
WATERS TUESDAY NIGHT. A DRY SLOT OF AIR LEADING THE CYCLONE WILL
PASS ACROSS THE STATE MONDAY AND BRIEFLY LOWER EARLY DAY RAIN
CHANCES. THEN RAIN CHANCES WILL STEADILY INCREASE FROM THE EAST
FROM LATE MONDAY THROUGH WEDNESDAY OR THURSDAY. LIGHT TRADES WILL
GRADUALLY BACK MORE NORTHERLY AS KIKO PASSES OFF TO THE NORTH
THROUGH THE MIDDLE OF THE WEEK. KIKO IS INTRODUCING A VERY HIGH
PRECIPITABLE WATER AIR MASS OF AROUND 2 INCHES TO THE AREA; NEAR
MAX VALUES BY EARLY SEPTEMBER STANDARDS. SO, WITH A FORECAST
NORTH-NORTHWEST KIKO TRACK, FORECAST CONFIDENCE IS THE GREATEST
THAT ISLAND WEATHER DURING KIKO'S PASSAGE WILL TRANSITION TO
CLOUDIER AND MORE HUMID UNDER VERY BENIGN WINDS AND OCCASIONAL
SHOWERS. THE GREATEST RAINFALL WILL LIKELY FALL ALONG MORE EASTERN
AND NORTHERN UPSLOPE MAUKA OR WITHIN HIGHER TERRAIN. THIS VERY
MOIST AIR MASS MOVING ACROSS THE ISLANDS AS KIKO PASSES TO THE
NORTH, COMBINED WITH WEAKER STEERING FLOW OVER THE ISLAND CHAIN,
MAY LEAD TO PERIODS OF HEAVY RAIN ALONG SMALL SCALE BREEZE
BOUNDARIES.
AS OF THIS MORNING, KIKO'S MAIN IMPACTS STILL REMAIN MARINE-BASED
AND FOCUSED ON POTENTIALLY HIGH EAST-FACING SHORE SURF (PLEASE
REFER TO THE MARINE SECTION BELOW FOR FURTHER DETAILS). WHILE
KIKO IS ANTICIPATED TO ARRIVE IN THE FAR OFFSHORE WATERS TUESDAY,
THERE IS ENOUGH INHERENT ERROR IN TRACK AND INTENSITY TO
UNDERSTAND THAT TROPICAL STORM FORCE CONDITIONS ARE POSSIBLE
(NON-ZERO CHANCES) ACROSS THE FAR WINDWARD NEARSHORE WATERS OF
BIG ISLAND AND MAUI COUNTY. THUS, INTERESTS IN HAWAII AND THE
SURROUNDING WATERS SHOULD CLOSELY MONITOR KIKO'S PROGRESSION
TOWARD THE STATE THESE NEXT COUPLE OF DAYS.
AVIATION
LIGHT AND VARIABLE TRADES WITH LAND/SEA BREEZES TODAY. LOW CIGS
AND SHRA POSSIBLE ALONG WINDWARD AND MAUKA AREAS. MVFR CONDS
POSSIBLE IN SHRA, OTHERWISE VFR SHOULD PREVAIL. A SLIGHT INCREASE
IN SHRA IS ANTICIPATED TOMORROW IN RELATION TO A TROUGH WEST
NORTHWEST OF HAWAII.
TROPICAL CYCLONE KIKO WILL APPROACH THE ISLAND CHAIN FROM THE
SOUTHEAST EARLY THIS WEEK. THE NATIONAL HURRICANE CENTER IS
CURRENTLY FORECASTING KIKO TO PASS NORTH OF THE ISLANDS TUESDAY.
ANY DEVIATION SOUTH OF THIS FORECAST TRACK MAY RESULT IN WIND AND
RAIN IMPACTS TO THE STATE.
NO AIRMETS ARE IN EFFECT.
MARINE
NO SIGNIFICANT CHANGES HAVE BEEN MADE TO THE FORECAST OVERNIGHT.
A WEAK TROUGH WILL LINGER NORTH OF THE STATE THROUGH TODAY,
RESULTING IN GENTLE TO MODERATE TRADE WINDS WITH LOCALIZED LAND
AND SEA BREEZES. AS THE TROUGH DRIFTS WESTWARD MONDAY, MORE
MODERATE TRADE WINDS COULD MAKE A BRIEF RETURN.
ATTENTION THEN TURNS TO HURRICANE KIKO, WHICH WAS LOCATED
APPROXIMATELY 640 NM ESE OF HILO EARLY THIS MORNING. HURRICANE
KIKO CONTINUES TO TRACK WEST NORTHWEST IN THE CENTRAL PACIFIC, AND
ACCORDING TO THE LATEST FORECAST FROM THE NATIONAL HURRICANE
CENTER, IS EXPECTED TO ENTER OUR OFFSHORE WATERS MONDAY NIGHT AS A
HURRICANE. KIKO WILL THEN CONTINUE TO MOVE NORTHWEST THROUGH THE
OFFSHORE WATERS AS IT WEAKENS TO TROPICAL STORM STATUS. THE LAST
FEW ADVISORIES FROM NHC HAVE CONSISTENTLY KEPT KIKO JUST FAR
ENOUGH AWAY TO KEEP THE MENTION OF POSSIBLE TROPICAL STORM
CONDITIONS OUT OF THE COASTAL WATERS FORECAST, BUT WE WILL
CONTINUE TO MONITOR FOR FUTURE TRACK UPDATES AS THE SYSTEM
APPROACHES. WITH THAT SAID, SWELL GENERATED BY KIKO WILL BEGIN
ARRIVING TODAY, PEAKING AT OR NEAR HIGH SURF WARNING LEVELS ALONG
EAST-FACING SHORES MONDAY NIGHT AND TUESDAY.
SURF ALONG EAST FACING SHORES WILL STEADILY RISE LATE TODAY
THROUGH THE NEXT COUPLE OF DAYS AS SWELL ENERGY FROM TROPICAL
CYCLONE KIKO ARRIVES. THE SURF MAY APPROACH HIGH SURF ADVISORY
CRITERIA AS EARLY AS MONDAY AND POSSIBLY REACH LOW END HIGH SURF
WARNING LEVELS MONDAY NIGHT INTO TUESDAY DURING ITS PEAK. SURF
HEIGHTS WILL BE HIGHLY DEPENDENT ON THE TRACK AND INTENSITY OF
KIKO AS IT NEARS THE STATE.
A MODERATE LONG PERIOD SOUTH-SOUTHWEST SWELL WILL PEAK TODAY
HELPING TO BUILD SURF ABOVE THE SUMMER AVERAGE. AS THIS SWELL
DECLINES ON MONDAY, ANOTHER REINFORCING SWELL OUT OF THE SOUTH-
SOUTHWEST IS EXPECTED ON TUESDAY. THIS SHOULD HELP MAINTAIN SURF
NEAR OR SLIGHTLY ABOVE THE SUMMER AVERAGE THROUGHOUT THE FIRST
HALF OF THE WEEK. ADDITIONALLY, MULTIPLE SMALL PULES OF NORTHWEST
SWELL ENERGY WILL GENERATE SMALL SURF ALONG NORTH FACING BEACHES
THROUGH NEXT WEEK.
PEAK MONTHLY HIGH TIDES, COMBINED WITH WATER LEVELS RUNNING
HIGHER THAN PREDICTED, MAY LEAD TO MINOR FLOODING ALONG THE
SHORELINE AND IN LOW LYING COASTAL AREAS. A COASTAL FLOOD
STATEMENT REMAINS IN EFFECT THROUGH THIS AFTERNOON.
FIRE WEATHER
WINDS WILL REMAIN WELL BELOW CRITICAL FIRE WEATHER THRESHOLDS
THE NEXT FEW DAYS. WHILE HUMIDITY LEVELS WILL STEADILY BE ON THE
RISE, THERE WILL BE BRIEF PERIODS OF LOW EARLY AFTERNOON
HUMIDITIES WITHIN LOWER ELEVATION, LEEWARD INTERIORS THE NEXT
COUPLE OF DAYS. DRIER AIR WILL FILTER IN ACROSS THE STATE MONDAY
AND MAINTAIN LOW HUMIDITY, BUT WINDS WILL REMAIN BELOW CRITICAL
FIRE WEATHER THRESHOLDS. SHOWERS MAY INCREASE IN COVERAGE AND
INTENSITY OVER MANY WINDWARD EXPOSURES BEGINNING LATE MONDAY
THROUGH THE MIDDLE OF THE WEEK AS A RESULT OF THE APPROACH AND
PASSAGE OF TROPICAL CYCLONE KIKO WELL NORTH OF THE STATE.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...BLOOD
AVIATION...WALSH
MARINE...VAUGHAN
FIRE WEATHER...BLOOD
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