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Hawaiian Islands Synoptic Discussion and Guidance

257
FXHW60 PHFO 051409
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
409 AM HST THU MAY 5 2016

.SYNOPSIS...
MOISTURE FROM AN OLD FRONT AND LIGHT WINDS WILL RESULT IN A UNSETTLE
WEATHER PATTERN FOR THE NEXT FEW DAYS. THEN A LATE SEASON FRONT
IS EXPECTED TO MOVE DOWN THE ISLAND CHAIN LATE FRIDAY... STALLING
OVER THE EASTERN PART OF THE CHAIN LATE IN THE WEEKEND. DRIER
WEATHER WITH MODEST TRADES WILL RETURN TO THE REMAINING ISLANDS BY
SUNDAY.

&&

.DISCUSSION...
SATELLITE IMAGERY SHOWS THE CLOUDS RESPONSIBLE FOR YESTERDAY/S
RAIN ON OAHU AND KAUAI...CONTINUES TO PUSH NORTH AND WEST OF KAUAI.
OAHU MOLOKAI AND LANAI...HAVE ALL CLEARED OUT NICELY. MAUI LOOKS
GOOD BUT IS BEING THREATEN BY SOME TRADE CLOUDS. WINDWARD BIG
ISLAND HAS HAD AN INCREASE IN CLOUDS IN THE PAST FEW HOURS...BUT
THEY APPEAR TO BE BREAKING UP. THE RAOB FROM HILO A COUPLE OF
HOURS AGO SHOWS A STRONG INVERSION AT 8100 FEET. THE INVERSION IS
STRONGER THAN THAT OF WEDNESDAY AFTERNOON. THE LIHUE SOUNDING ALSO
HAS AN INVERSION BASED AT 8700 FEET...ALSO STRONGER TO THAT OF 12
HOURS AGO. SO IT APPEARS SUBSIDENCE IS PRESENT AROUND THE ISLANDS...
LEADING TO A RATHER QUIET THURSDAY MORNING.

THE CURRENT WIND SITUATION IS EAST SOUTHEAST AREA WIDE. IT IS
EXPECTED TO VEER TO THE SOUTHEAST ACROSS THE SMALLER ISLANDS AS
THE DAY PROGRESSES...WHILE WINDWARD BIG ISLAND WILL STILL BE
FEELING AN EASTERLY WIND FLOW. TONIGHT...THE WINDS SHIFTS TO
LIGHT SOUTHERLY ACROSS THE SMALLER ISLANDS...FOLLOW BY LIGHT
WESTERLIES FRIDAY ACROSS THE CENTRAL ISLANDS. WINDS ACROSS KAUAI
WILL BE SOUTHERLY WITH A FRONT CLOSING IN FRIDAY AFTERNOON.
THE BIG ISLAND HAS WINDS SHIFTING TO THE SOUTHEAST AND SOUTH
FRIDAY THROUGH FRIDAY NIGHT.

HAVING SAID THIS...THE WINDS WILL BE LIGHT ENOUGH OVER KAUAI OAHU
MOLOKAI AND LANAI TODAY FOR SEAS BREEZES TO DEVELOP LATER THIS
MORNING. WITH THE AMPLE MOISTURE...THE LEEWARD/INTERIOR WILL HAVE
A FEW SHOWERS THIS AFTERNOON..THAT IS IF THE INVERSION WEAKENS. A
LAND BREEZE WILL LIKELY TAKE OVER THIS EVENING RESULTING IN FAIR
OVERNIGHT SKIES AND AN ISOLATED SHOWER AT BEST. OVER ON MAUI...THERE
WILL BE SUFFICIENT SOUTHEAST WINDS BLOWING ACROSS THE WINDWARD WATERS
OF MAUI THIS AFTERNOON AND EVENING RESULTING IN A FEW WINDWARD SHOWERS.

WITH THE LIGHTER WINDS ON TAP FOR ALMOST EVERYWHERE FRIDAY...MAUI
AND THE BIG ISLAND WILL LIKELY JOIN OAHU WITH AFTERNOON CONVECTIVE
SHOWERS. A MORE ORGANIZED BAND OF MOISTURE IS SLATED TO REACH
THE WINDWARD SIDE OF MAUI AND THE BIG ISLAND LATER FRIDAY EVENING
FROM THE EAST THAT WILL PERSIST INTO SATURDAY.

AT THE OTHER END OF THE ISLAND CHAIN...A FRONT WILL REACH KAUAI
FRIDAY AFTERNOON. THE FRONT WILL DISSIPATE AS MOVES ON TO
OAHU...REACHING THAT ISLAND EARLY SATURDAY MORNING. THE REMNANT
FRONT WILL REACH MAUI COUNTY LATE SATURDAY MORNING...JOINING UP
WITH MOISTURE THAT HAD ARRIVED EARLIER. THE MODELS CONCUR WITH THE
FRONT GETTING HUNG UP OVER EAST MAUI AND THE BIG ISLAND SATURDAY
NIGHT INTO SUNDAY...AND PERHAPS EVEN LONGER...INTO MONDAY.

A DRIER TRADE WIND REGIME WITH A SLIGHTLY COOLER AIR MASS WILL
FOLLOW IN BEHIND THE FRONT. GFS HAS DEW POINTS LOWERING FROM THE
MID 60/S TO THE LOWER 60S SATURDAY NIGHT FOR KAUAI AND OAHU. AIR
TEMPS WILL BE A COUPLE OF DEGREES COOLER THROUGH EARLY NEXT WEEK.

THE SHOWERS IN THE FORECAST FOR THE NEXT FEW DAYS WILL NOT HAVE
MUCH OF ANY UPPER LEVEL SUPPORT. MODEL DERIVED CROSS SECTION OF
THE MOISTURE FIELD ACROSS THE ISLAND CHAIN SHOW MOISTURE CAPPED
AT 10 TO 12K FEET.


&&

.AVIATION...
MUCH OF THE LOW CLOUDS HAVE PRETTY MUCH CLEAR MOST OF THE ISLANDS
EARLY THIS MORNING...EXCEPT KAUAI. IT WILL PROBABLY BE A FEW MORE
HOURS BEFORE KAUAI AND VICINITY TO BE CLEAR. THE NEXT AREA OF LOW
CLOUDS IS JUST EAST OF THE STATE AND WILL REACH THE ISLANDS LATER
THIS MORNING. EXPECT THE CLOUDINESS TO BE LESS EXTENSIVE...THOUGH
ISOL MVFR CEILING CONDITION AS WELL AS SOME SHRA ARE STILL
POSSIBLE...ESPECIALLY FOR THE EASTERN PART OF THE ISLANDS. THUS
AIRMET MTN OBSC FOR E KAUAI WILL LIKELY BE DROPPED IN THE COMING
HOURS.

MAINLY VFR CONDITIONS ARE EXPECTED FOR THE STATE.

WINDS WILL CONTINUE TO TURN MORE SOUTHEASTERLY AS A SURFACE HIGH
PRESSURE RIDGE FROM THE NORTH MOVES CLOSER TO THE ISLANDS.


&&

.MARINE...
A SMALL NORTHWEST BUMP IS CURRENTLY PEAKING. A GRADUAL DROP IS
EXPECTED THE REST OF TODAY. A REINFORCING NORTHWEST SWELL OF
MODERATE SIZE AND A MORE NORTH COMPONENT IS DUE IN FRIDAY EVENING
AND SATURDAY...LASTING INTO SUNDAY. THE SOUTH FACING SHORES WILL
HAVE SOME WAVES AS WELL. A GOOD SIZE BUMP IS SLATED TO START
ROLLING IN THURSDAY WITH SURF HEIGHTS BUILDING TO AT OR NEAR
ADVISORY LEVEL FOR THE SOUTH FACING SHORES AS EARLY AS SATURDAY.
ANOTHER FOOT RISE FROM 3 TO 4 FEET WITH A 15 SECONDS PERIOD IS
SLATED TO COME IN SATURDAY NIGHT CONTINUING THROUGH MOST OF
SUNDAY BEFORE THE DECLINING PHASE KICKS IN.

ALTHOUGH WE ARE CURRENTLY CALLING FOR NO SMALL CRAFT ADVISORY
/SCA/ EVEN WITH THE NORTHEAST WINDS...WE WILL BE WATCHING CLOSELY
FOR ANY SIGNS. AS OF NOW...IT LOOKS THE MAX STRENGTH OF THE
NORTHEAST WIND IS MARGINAL SMALL CRAFT.

&&

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

&&

$$

DISCUSSION/MARINE...LAU
AVIATION...HUI

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office