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Hawaiian Islands Synoptic Discussion and Guidance

033
FXHW60 PHFO 301330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST SAT MAY 30 2015

.SYNOPSIS...
THE LIGHT TO MODERATE TRADES CONTINUE THROUGH THE REST OF THE
WEEKEND. ONLY EXCEPTION WILL BE AROUND THE BIG ISLAND WHERE LIGHT
AND VARIABLE WINDS WILL PREVAIL. THE TRADE WINDS WILL CONTINUE TO
BRING CLOUDS AND SHOWERS OVER WINDWARD AND MOUNTAIN AREAS...WITH
HIGHER CHANCES OF RAIN OVER KAUAI AND OAHU. SEA BREEZES WILL ALSO
BRING AFTERNOON AND EARLY EVENING PERIODS OF CLOUDS AND SHOWERS OVER
LEEWARD AREAS...WITH GENERALLY CLEAR SKIES DURING THE NIGHTS AND
MORNINGS.

&&

.DISCUSSION...
LIGHT TO MODERATE TRADES CONTINUE TODAY...STRONGER AROUND KAUAI AND
OAHU...AND TURNING MORE NORTHERLY NEAR THE BIG ISLAND. MODEL AND
SATELLITE DATA STILL SUGGEST THE PRESENCE OF A WEAKENING SFC TROUGH
EXTENDING NE FROM NEAR THE BIG ISLAND. THIS FEATURE CONTINUES TO
KEEP HIGHER THAN NORMAL MOISTURE UPSTREAM AND AROUND THE ISLAND
CHAIN. MEANWHILE...LATEST WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL
TROUGH AROUND 400 MILES NE OF THE ALOHA STATE GRADUALLY MIGRATING
FURTHER E...ALLOWING FOR GRADIENTS ALOFT TO RELAX. THUS...THE STRONG
WINDS OVER THE BIG ISLAND SUMMITS ARE NOW SUBSIDING.

THE LIGHT TO MODERATE NE WINDS WILL ALSO KEEP PASSING SHOWERS AND
CLOUDS OVER WINDWARD AND MOUNTAIN AREAS...ESPECIALLY OAHU AND KAUAI
FOR THE NEXT COUPLE OF DAYS. ON THE OTHER HAND...LAND BREEZES SHOULD
ALSO HELP IN CLEARING OUT MOST LEEWARD LOCATIONS OF THE SMALLER
ISLANDS AT NIGHT.

THE CURRENT LIGHT TO MODERATE TRADE WIND REGIME IS EXPECTED TO
PREVAIL THROUGH THE REST OF THE WEEKEND AS HIGH PRESSURE REMAINS
LOCATED TO THE NW OF THE ISLANDS. MEANWHILE...A BAND OF ENHANCED
MOISTURE IS APPROACHING THE ISLANDS FROM THE N...WITH GUIDANCE
BRINGING THIS BAND INTO THE VICINITY OF KAUAI LATER THIS MORNING.
THE COMBINATION OF THIS ENHANCED MOISTURE AND DEVELOPING SEA BREEZES
COULD BRING ACTIVE AFTERNOON AND EARLY EVENING SHOWER PERIODS OVER
LEEWARD AREAS OF THE SMALLER ISLANDS TODAY AND AGAIN SUN.

PRESSURE GRADIENTS ACROSS THE AREA SHOULD REMAIN WEAK ENOUGH TO KEEP
THE TRADES GENERALLY LIGHT TO MODERATE THROUGH AT LEAST THE FIRST
HALF OF NEXT WEEK. THE AFOREMENTIONED HIGH NW OF THE ISLANDS WILL
GRADUALLY MIGRATE E DURING THE NEXT SEVERAL DAYS...WHILE THE
WEAKENING SFC TROUGH NE OF THE BIG ISLAND OR ITS REMNANTS SEEM TO
DRIFT W AND OVER THE SMALLER ISLANDS. IN ADDITION...MODELS SHOW A
SHARP MID-LEVEL TROUGH MOVING W TO E ACROSS THE AREA DURING THE
WEEKEND AND INTO EARLY NEXT WEEK. THIS SYNOPTIC SCENARIO COULD
FURTHER ENHANCE SHOWER ACTIVITY IN ADDITION TO THE SEA BREEZE
CONVECTION.

LATEST MODEL GUIDANCE SUGGEST THE RETURN OF A FAIRLY SEASONABLE
TRADE WIND PATTERN FOR THE MIDDLE AND LATTER PART OF NEXT WEEK.

&&

.AVIATION...
A PIECE FROM A FRAGMENTED BAND OF LOW CLOUDS AND A FEW EMBEDDED
SHOWERS IS CURRENTLY MOVING THROUGH KAUAI...RESULTING IN SOME
LIGHT SHOWERS TO ITS WINDWARD AND MTN AREAS. ADDITIONAL AREAS OF LOW
CLOUDS LIES UPWIND OF THE ISLAND THAT WILL MOVE ASHORE LATER THIS
MORNING. WE WILL BE MONITORING WHETHER AN AIRMET SIERRA FOR MTN
OBSCURATION IS NEEDED.

THE DAYTIME CLOUDS FROM FRIDAY CONTINUES TO LINGER AROUND THE
WINDWARD SIDE OF MAUI AND THE BIG ISLAND. THE CLOUDS ARE MAINLY HIGH
BASE STRATOCUMULUS...ABOVE 3K FEET...SO AIRMET SIERRA IS NOT NEEDED.
AN AREA OF BROKEN LOW CLOUDS PERSISTED OVER THE WATERS OFF THE KONA
COAST. THESE CLOUDS WILL BE DISSIPATING AS WE APPROACH SUNRISE.

OTHERWISE...VFR CONDS RULE THE ISLAND SKIES. THERE ARE SOME
SCATTERED MOSTLY LIGHT SHOWERS MOVING IN WITH THE NE WIND FLOW...
FAVORING THE WINDWARD MTN AND COMMUNITIES. NO RESTRICTION TO VIS
WITH THESE SHOWERS BUT BRIEF MVFR CEILINGS ARE EXPECTED. MODELS ARE
INDICATING ADDITIONAL SHOWERS WILL BE SPREADING EWD FROM KAUAI
THROUGH OUT THE DAY. THE KONA SLOPES WILL HAVE SOME AFTERNOON BROKEN
TO OVC LOW CLOUDS BUT THE CLOUD BASES SHOULD REMAIN ABOVE 3K FEET.


&&

.MARINE...
A LONGER-PERIOD SSW SWELL WILL ARRIVE ON SUNDAY...BRINGING SURF
HEIGHTS INTO ADVISORY LEVELS ALONG SOUTH FACING SHORES THROUGH
TUESDAY. PEAK OPEN OCEAN SWELL HEIGHTS WILL REACH AROUND 5 FEET.
THIS SWELL MAY CAUSE SURGES IN HARBORS EXPOSED TO THE SOUTH...AND
BREAKING WAVES IN AND NEAR SOUTH FACING CHANNEL ENTRANCES. MARINERS
AND BEACHGOERS SHOULD BE ALERT TO THE FACT THAT THIS IS LIKELY TO BE
THE LARGEST SOUTH SWELL OF THE SEASON THUS FAR. EXTREME TIDAL
CHANGES WILL ALSO LEAD TO LOCALLY STRONG CURRENTS. ALTHOUGH A LITTLE
TOO EARLY TO ISSUE A HIGH SURF ADVISORY...A MARINE WEATHER STATEMENT
HAS BEEN ISSUED TO HELP INCREASE AWARENESS.

OTHERWISE...SMALL AND RELATIVELY SHORT-PERIOD WNW SWELLS WILL
ARRIVE OVER THE NEXT COUPLE OF DAYS...SUPPORTING SMALL SURF ALONG N
FACING SHORES. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY /SCA/ LEVELS THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK...AFTER WHICH STRONGER TRADE WINDS MAY NECESSITATE A SCA
ISSUANCE IN THE WINDIER MARINE ZONES AROUND MAUI AND THE BIG ISLAND.

&&

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

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...LAU






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