813
FXHW60 PHFO 161329
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
329 AM HST WED JUL 16 2025
SYNOPSIS
THE HIGH PRESSURE RIDGE WILL REMAIN IN PLACE NORTH OF THE HAWAIIAN
ISLANDS INTO THE FIRST HALF OF NEXT WEEK. EXPECT BREEZY TRADE
WINDS TODAY AND TOMORROW, BECOMING MORE MODERATE TRADE WINDS FROM
FRIDAY THROUGH SUNDAY, THEN MODERATE TO BREEZY AGAIN FROM MONDAY
ONWARD. WEATHER WISE VERY STABLE CONDITIONS PERSIST FOR MOST OF
THE WEEK, WITH A SLIGHT INCREASE IN CLOUDS AND SHOWERS FOR
WINDWARD MOUNTAIN AREAS ON FRIDAY AND SATURDAY. STABLE WEATHER
CONDITIONS RETURN FROM SUNDAY ONWARD AS AN UPPER LEVEL RIDGE
BUILDS OVER THE REGION.
DISCUSSION
THE SUBTROPICAL RIDGE WILL REMAIN IN PLACE NORTH OF THE HAWAIIAN
ISLANDS THROUGH THE FIRST HALF OF NEXT WEEK. EASTERLY TRADE WINDS
WILL START OFF IN THE MODERATE TO BREEZY RANGE THROUGH THURSDAY,
THEN DROP SLIGHTLY BACK TO MORE MODERATE RANGES FROM FRIDAY
THROUGH SUNDAY, AND FINALLY INCREASE BACK INTO THE MODERATE TO
LOCALLY BREEZY RANGE FROM NEXT WEEK MONDAY ONWARD. SATELLITE
IMAGERY THIS MORNING SHOWS AN EXTENSIVE BLANKET OF STABLE
STRATOCUMULUS CLOUDS IN THE UPSTREAM TRADE WIND FLOW. THESE STABLE
CLOUDS ARE CAPPED BY A STRONG 5,000 FOOT SUBSIDENCE TEMPERATURE
INVERSION, LIMITING VERTICAL CLOUD DEVELOPMENT AND KEEPING DRIER
CONDITIONS IN THE FORECAST THROUGH THURSDAY.
IN THIS SUMMER TRADE WIND WEATHER PATTERN WE LOOK FOR SUBTLE
CHANGES IN THE FORECAST GUIDANCE TO PICK OUT SLIGHT DAY TO DAY OR
ISLAND BY ISLAND CHANGES. ONE OF THOSE SLIGHT CHANGES STARTS ON
FRIDAY MORNING AS OUR CONFIDENCE GROWS THAT DIVERGENCE BETWEEN AN
UPPER LEVEL TROUGH THE SUBTROPICAL JET STREAM WILL COMBINE FORCES
WITH A WEAK LOW LEVEL TROUGH RIDING INTO THE ISLANDS ON THE TRADE
WINDS. THIS COMBINATION OF UPPER LEVEL AND LOW LEVEL FORCING WILL
LIFT THE TEMPERATURE INVERSION HEIGHTS TO AROUND THE 7,000 FOOT
RANGE, SLIGHTLY INCREASING PASSING RAINFALL ACTIVITY INTO THE
SCATTERED TO NUMEROUS RANGE, MAINLY OVER WINDWARD AND MOUNTAIN
AREAS IN THE OVERNIGHT TO EARLY MORNING HOURS. HIGH LEVEL CIRRUS
CLOUDS WILL DEVELOP OVER ALL ISLANDS IN THIS WEATHER PATTERN,
COURTESY OF THE SUBTROPICAL JET. NOT MUCH IN THE WAY OF RAINFALL
TOTALS ARE EXPECTED IN THE FRIDAY AND SATURDAY TIME PERIOD,
PROBABLY LESS THAN 0.10 INCH OVER A 12 HOUR OVERNIGHT TIME PERIOD
FOR MOST WINDWARD MOUNTAIN LOCATIONS AND UP TO 0.50 INCH AMOUNTS
FOR THE TERRAIN FAVORED WETTEST LOCATIONS.
STABLE SUMMERTIME WEATHER CONDITIONS PREDICTABLY RETURN BY SUNDAY
AS A HIGH PRESSURE RIDGE BUILDS DIRECTLY OVER THE HAWAII REGION.
THIS RIDGE ALOFT WILL INCREASE DOWNWARD VERTICAL MOTIONS
(SUBSIDENCE) EFFECTIVELY LOWERING THE TEMPERATURE INVERSION
HEIGHTS BACK DOWN TO AROUND THE 5,000 FOOT ELEVATION LEVEL AND
SEVERELY LIMITING SHOWER OPPORTUNITIES FROM SUNDAY ONWARD.
AVIATION
A HIGH PRESSURE RIDGE REMAINS IN PLACE NORTH OF THE HAWAIIAN
ISLANDS THIS WEEK. MODERATE TO BREEZY EASTERLY TRADE WINDS REMAIN
IN THE FORECAST. WEATHER CONDITIONS WILL REMAIN ON THE STABLE
SIDE THROUGH THURSDAY WITH LIMITED CLOUDS AND SHOWERS.
NO AIRMETS CURRENTLY IN EFFECT. AIRMET TANGO MAY BE NEEDED LATER
TODAY FOR MODERATE LOW LEVEL TURBULENCE OVER AND SOUTH THROUGH
WEST OF ISLAND MOUNTAINS AS WIND SPEEDS INCREASE OVER THESE
HIGHER TERRAIN FEATURES.
MARINE
HIGH PRESSURE WILL REMAIN FAR NORTHEAST OF THE STATE THROUGHOUT
THE WEEK. FRESH TO LOCALLY STRONG TRADES WILL LIKELY PERSIST
THROUGH MOST OF THE WEEK, ALTHOUGH WE COULD SEE WIND SPEEDS DROP
SLIGHTLY AS A WEAK TROUGH DEVELOPS NEAR THE WESTERN END OF THE
STATE INTO THE WEEKEND. A SMALL CRAFT ADVISORY (SCA) IS IN EFFECT
FOR THE TYPICAL WINDY AREAS AROUND MAUI COUNTY AND THE BIG ISLAND
THROUGH THURSDAY NIGHT.
A SHORT-PERIOD SOUTH-SOUTHEAST SWELL WILL CONTINUE TO FILL IN
TODAY, SLOWING THE DECLINE OF SURF HEIGHTS THROUGH FRIDAY.
ANOTHER SMALL INCREASE IS EXPECTED HEADING INTO THE WEEKEND AS A
NEW LONG- PERIOD SOUTHWEST SWELL ARRIVES FROM THE TASMAN SEA.
SURF ALONG EAST FACING SHORES WILL CONTINUE TO REMAIN ROUGH AND CHOPPY
WITH A SLIGHT BOOST IN SURF HEIGHTS EXPECTED THROUGH MID WEEK AS
THE TRADES STRENGTHEN AND AGAIN LATE THIS WEEK INTO THE WEEKEND
AS A SHORT-PERIOD NORTHEAST SWELL FILLS IN. SURF ALONG NORTH
FACING SHORES WILL CONTINUE TO DECLINE THROUGH WEDNESDAY AND
REMAIN NEARLY FLAT THROUGH THE WEEKEND.
FIRE WEATHER
TRADE WINDS WILL REMAIN IN THE MODERATE TO LOCALLY BREEZY RANGE
THROUGH THE FORECAST PERIOD. SHOWER TRENDS MAY INCREASE FROM
FRIDAY MORNING INTO SATURDAY NIGHT AS A COMBINATION OF UPPER AND
LOW LEVEL DISTURBANCES MOVE INTO THE ISLANDS. DRIER AND MORE
STABLE WEATHER RETURNS FROM SUNDAY ON INTO THE MIDDLE OF NEXT
WEEK WITH BORDERLINE FIRE WEATHER CONCERNS OVER LEEWARD AREAS.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 PM HST THURSDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...BOHLIN
AVIATION...BOHLIN
MARINE...WALSH
FIRE WEATHER...BOHLIN
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