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FXHW60 PHFO 172002
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1002 AM HST WED SEP 17 2014

.SYNOPSIS...
WEAK SURFACE HIGH PRESSURE NORTH OF THE ISLANDS WILL MAINTAIN
GENTLE TRADE WINDS ACROSS THE STATE TODAY...WITH LOCALIZED
AFTERNOON SEA BREEZES DEVELOPING. THE RIDGE WILL BREAK DOWN FROM
THURSDAY INTO THE WEEKEND...ALLOWING FOR WIDESPREAD SEA BREEZES
ALONG WITH AFTERNOON CLOUDS AND SHOWERS. DRY AND STABLE AIR ALOFT
WILL KEEP MOST RAINFALL AMOUNTS LIGHT. A TROPICAL WAVE PASSING
SOUTH OF THE AREA MAY BRING AN INCREASE IN RAINFALL...ESPECIALLY
ACROSS THE BIG ISLAND...WITH GENTLE TRADE WINDS RESUMING ACROSS
THE STATE BY THE LATER HALF OF THE WEEKEND AND INTO EARLY NEXT
WEEK.

&&

.DISCUSSION...
VISIBLE SATELLITE IMAGERY SHOWS MOSTLY SUNNY SKIES OVER THE ISLANDS WHILE
SCATTERED CUMULUS CLOUDS ARE LOCATED MAINLY OVER THE WINDWARD WATERS
OF THE SMALLER ISLANDS THIS MORNING. RADAR IS PICKING UP ISOLATED
SHOWERS WITHIN THESE CLOUDS WHICH ARE GENERALLY MOVING NORTHEAST
TO SOUTHWEST AT 5 TO 10 MPH. GENTLE TRADE WINDS OVER HAWAII ARE
DRIVEN BY A 1022 MB SURFACE HIGH LOCATED FAR TO THE NORTH-NORTHWEST.

ALOFT...A WEAK UPPER LEVEL LOW IS CENTERED NEAR KAUAI...WITH A
LARGE MID/UPPER LEVEL RIDGE SPRAWLING NORTHWEST OF OUR REGION FROM
WEST OF THE DATELINE TO NEAR 160W. MIMIC-TOTAL PRECIPITABLE WATER
/PW/ SATELLITE IMAGERY SHOWS A STRIPE OF HIGHER MOISTURE
ASSOCIATED WITH THE CLOUDS JUST NORTH OF THE SMALLER ISLANDS. THIS
AREA OF MOISTURE IS MOVING TO THE WEST-SOUTHWEST TOWARDS KAUAI AND
OAHU. THE 12Z SOUNDINGS DEPICT A RATHER TYPICAL PROFILE...WITH
INVERSIONS BASED AROUND 7000 FEET...AND NEAR NORMAL PW VALUES
BETWEEN 1.3 AND 1.5 INCHES.

FOR TODAY...EXPECT ANOTHER WARM DAY ACROSS THE STATE. THE LIGHT
TRADE WIND FLOW WILL ALLOW FOR LEEWARD SEA BREEZES TO OVER POWER
THE FLOW RESULTING IN AFTERNOON CLOUDS OVER LEEWARD / INTERIOR
SECTIONS. A FEW LEEWARD SHOWERS ARE POSSIBLE BY THE AFTERNOON TIME
PARTICULARLY ACROSS KAUAI AND OAHU WITH THE HIGHER MOISTURE TO THE
NORTH ADVECTING IN TODAY.

THURSDAY THROUGH THE WEEKEND....THE HIGH TO THE NORTHWEST IS
FORECAST TO MOVE EAST AND QUICKLY WEAKEN OVER THE NEXT 24 HOURS AS
A COLD FRONT DROPS SOUTHEASTWARD ACROSS THE NORTH CENTRAL PACIFIC.
THE RESULT WILL BE EVEN LIGHTER WINDS AND A PURE SEA AND LAND
BREEZE PATTERN. THIS PATTERN WILL BRING MOSTLY CLEAR NIGHTS AND
MORNINGS WITH SPOTTY SHOWERS OVER INTERIOR AREAS DURING THE
AFTERNOONS AND EVENINGS. THE LIGHT WINDS WILL ALLOW VOLCANIC HAZE
TO BUILD UP AROUND THE BIG ISLAND...BUT IT DOES NOT APPEAR AS IF
THERE WILL BE ENOUGH SOUTHERLY COMPONENT IN THE FLOW TO CARRY THE
HAZE OVER THE SMALLER ISLANDS.

GFS AND ECMWF COMING INTO LINE FOR A TROPICAL WAVE PASSING SOUTH
OF THE STATE SUNDAY...WITH BOTH MODELS SUGGESTING THAT NORTHERN
FRINGES OF THE PLUME OF MOISTURE WILL BARELY BRUSH ACROSS THE BIG
ISLAND. THIS MAY BRING AN INCREASE IN SHOWERS AT THIS TIME. IT
ALSO APPEARS THE FRONT WILL STALL OUT AND DISSIPATE ABOUT 300
MILES NORTH OF THE STATE. THE INCREASED PRESSURE GRADIENT BETWEEN
LOWER PRESSURE TO THE SOUTH...AND A NARROW HIGH PRESSURE RIDGE
BETWEEN THE ISLANDS AND A STALLED FRONTAL BOUNDARY TO OUR NORTH
SHOULD INDUCE SOME INCREASE IN EASTERLY FLOW OVER THE STATE DURING
BY MONDAY.

UNCERTAINTY INCREASES FURTHER FOR NEXT TUESDAY AND BEYOND...WHEN
THE GFS DROPS ANOTHER COLD FRONT SOUTHWARD INTO THE CENTRAL
PACIFIC...WEAKENING AND VEERING OUR LOCAL WIND FLOW TOWARD THE
SOUTHEAST. THE ECMWF HAS A COMPLETELY DIFFERENT SOLUTION FOR THIS
TIME PERIOD WITH A BUILDING HIGH PRESSURE RIDGE IN THE CENTRAL
PACIFIC...CAUSING INCREASING TRADES OVER THE STATE. WILL HAVE TO
AWAIT FUTURE MODEL RUNS WHICH WILL HOPEFULLY RESOLVE THESE
DIFFERENCES.


&&

.AVIATION...
LIGHT TRADE WINDS AND VFR CONDITIONS WILL CONTINUE TODAY. LOCALLY...
SEABREEZES WILL DEVELOP... PRODUCING INTERIOR CLOUD BUILDUPS AND
SHOWERS THIS AFTERNOON. THIS ACTIVITY WILL SUBSIDE WITH SUNSET.
OTHERWISE... CLOUDS AND SHOWERS WILL FOCUS OVER WINDWARD SLOPES...
BEING MOST PREVALENT DURING THE NIGHT AND EARLY MORNING HOURS.


&&

.MARINE...
OBSERVATIONS FROM THE BARBERS POINT BUOY THIS MORNING SHOW THE
SOUTH SWELL CONTINUING TO SLOWLY DECLINE...WITH PEAK ENERGY VALUES
GRADUALLY SHIFTING INTO THE SHORTER WAVE PERIOD BANDS. THIS SWELL
WILL SLOWLY FADE AWAY THROUGH FRIDAY. SURF ALONG SOUTH FACING
SHORES WILL REMAIN SOMEWHAT ELEVATED THROUGH TODAY...BUT SHOULD
STAY BELOW ADVISORY CRITERIA. ANOTHER SMALL SOUTH SWELL WILL BUILD
IN LATE THIS AFTERNOON OR EVENING.

ELSEWHERE...A SMALL NORTHWEST SWELL ARRIVED LATE YESTERDAY...AS
INDICATED BY WAIMEA BAY BUOY DATA. ANOTHER SMALL NORTHWEST SWELL
WILL ARRIVE LATER TODAY...BUT SURF ALONG NORTH FACING SHORES WILL
REMAIN WELL BELOW ADVISORY LEVELS.

AN 0806Z ASCAT PASS FOUND GENTLE TO LOCALLY MODERATE TRADE WINDS
ACROSS THE HAWAIIAN COASTAL WATERS...WITH A SMALL AREA OF WINDS
GREATER THAN 15 KNOTS IN THE ALENUIHAHA CHANNEL. THESE WILL
PROBABLY BE THE STRONGEST WINDS SEEN IN OUR WATERS THROUGH THE
NEXT SEVERAL DAYS...WITH WIND SPEEDS EXPECTED TO BEGIN DECREASING
LATER TODAY. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY LEVELS THROUGH AT LEAST EARLY NEXT WEEK.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION/MARINE...FOSTER
AVIATION...EATON





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