Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 300153
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
353 PM HST FRI MAY 29 2015

.SYNOPSIS...
LIGHT TO MODERATE TRADE WINDS WILL RETURN TO MOST AREAS THIS
WEEKEND...BUT WINDS WILL REMAIN LIGHT AND VARIABLE OVER THE BIG
ISLAND FOR A COUPLE MORE DAYS. THE TRADE WINDS WILL DELIVER CLOUDS
AND SHOWERS TO WINDWARD SLOPES AND COASTS...AND WILL BE ESPECIALLY
ACTIVE FROM KAUAI TO MAUI THIS WEEKEND. THE LIGHT WINDS WILL ALLOW
CLOUDS AND A FEW SHOWERS TO DEVELOP OVER LEEWARD AREAS IN THE
AFTERNOONS...WITH GENERALLY CLEAR SKIES DURING NIGHTS AND MORNINGS.

&&

.DISCUSSION...
CURRENTLY...LIGHT TO MODERATE TRADES ARE FAVORING A NE DIRECTION
NEAR KAUAI AND OAHU...WHILE LIGHTER N WINDS ARE IN PLACE NEAR THE
BIG ISLAND. THESE WINDS ARE DUE TO A PERSISTENT SURFACE TROUGH THAT
EXTENDS NE FROM NEAR THE BIG ISLAND...AND HIGH PRESSURE CENTERED TO
THE DISTANT NW OF KAUAI...WITH THE SURFACE GRADIENT OVER THE ISLANDS
MUCH LOOSER THAN NORMAL. MIMIC-TPW IMAGERY AND AFTERNOON SOUNDINGS
BOTH INDICATE A SLIGHTLY GREATER THAN NORMAL AMOUNT OF ATMOSPHERIC
MOISTURE IN PLACE NEAR THE ISLANDS...WITH VALUES RANGING FROM 1.3 TO
1.7 INCHES. WATER VAPOR IMAGERY DEPICTS A WEAK TROUGH ALOFT
EXTENDING OVER THE BIG ISLAND FROM THE NE...WHICH HAD BEEN
SUPPORTING ADVISORY LEVEL WIND SPEEDS OVER THE BIG ISLAND SUMMITS...
ALTHOUGH WINDS HAVE TRENDED DOWN OVER THE PAST COUPLE OF HOURS.

OVERNIGHT...THE GRADUALLY WEAKENING TROUGH ALOFT SHOULD LEAD TO
DIMINISHING WINDS OVER THE SUMMITS...AND THE WIND ADVISORY HAS BEEN
CANCELLED. THE LIGHT LOW-LEVEL WINDS OVER THE BIG ISLAND SHOULD
ALLOW SKIES TO GRADUALLY CLEAR THROUGH THE EVENING...WHILE THE LIGHT
TO MODERATE NE WINDS OVER THE OTHER ISLANDS WILL DELIVER WINDWARD
CLOUDS AND A FEW SHOWERS. WINDWARD SHOWERS ARE EXPECTED TO BE ON THE
INCREASE OVER WINDWARD KAUAI AND OAHU LATE IN THE NIGHT. LEEWARD
AREAS SHOULD CLEAR OVERNIGHT...AS LOCAL LAND BREEZES HELP TO CLEAR
THINGS OUT.

LIGHT TO MODERATE TRADES WILL PREVAIL OVER MOST OF THE STATE THIS
WEEKEND...AS HIGH PRESSURE BUILDS TO THE NW AND A TROUGH PERSISTS TO
THE NE. WINDS NEAR THE BIG ISLAND WILL REMAIN ON THE LIGHTER SIDE
WHILE FAVORING A NE DIRECTION OVER WATER. WITH STRONGER WINDS TO THE
N AND LIGHTER WINDS TO THE S...MODEL GUIDANCE DEVELOPS AN E-W
MOISTURE CONVERGENCE BOUNDARY NEAR THE ISLANDS OVER THE NEXT 12-72
HOURS...WITH THE SOURCE APPARENTLY RELATED TO A FRAGMENTED BAND OF
SHOWERY LOW CLOUDS CURRENTLY ABOUT 100 TO 200 MILES N OF KAUAI AND
OAHU. GUIDANCE INDICATES THIS BAND WILL CONTINUE TO SAG S TOWARD THE
ISLANDS OVERNIGHT...AND BE NEAR KAUAI AND OAHU EARLY SATURDAY.
MOISTURE ASSOCIATED WITH THIS BOUNDARY IS DENOTED AS MOVING OVER
OAHU AND MAUI THROUGH SATURDAY NIGHT...THEN LINGERING OVER ALL
ISLANDS FROM MAUI TO KAUAI THROUGH MONDAY. THIS WILL FUEL MOSTLY
WINDWARD SHOWERS...BUT RELATIVELY WEAK WINDS WILL COMBINE WITH AN
ELEVATED INVERSION TO ALLOW CLOUDS AND A FEW SHOWERS TO DEVELOP OVER
LEEWARD AREAS IN THE AFTERNOONS.

ALTHOUGH TRADE WINDS ARE ATTEMPTING TO BECOME RE-ESTABLISHED...
THEY LOOK TO REMAIN ON THE LIGHTER END OF THE SPECTRUM INTO THE
MIDDLE OF NEXT WEEK...AS THE SURFACE HIGH SHIFTS NE...AND A WEAK
REMNANT OF THE SURFACE TROUGH NE OF THE BIG ISLAND SHIFTS W OVER
THE OTHER ISLANDS. IT MAY BRIEFLY SHARPEN IN RESPONSE TO A
PROGRESSIVE MID-LEVEL TROUGH THAT SHARPENS W OF THE AREA OVER THE
WEEKEND...AND PASSES FROM W TO E ACROSS THE AREA EARLY NEXT WEEK.
COMBINED WITH AMPLE LOW-LEVEL MOISTURE...THIS COULD RESULT IN
ENHANCED SHOWERS...BOTH IN THE TYPICAL WINDWARD/MAUKA AREAS...AND
OVER INTERIOR/LEEWARD AREAS ALONG LOCAL SEA BREEZE BOUNDARIES DURING
THE AFTERNOONS. LATEST MODEL GUIDANCE INDICATES A FAIRLY SEASONABLE
TRADE WIND PATTERN FOR THE MIDDLE AND LATTER PART OF THE NEXT
WEEK...WITH LIGHT TO MODERATE TRADE WINDS.

&&

.AVIATION...
THE LIGHT TRADE WINDS ALLOWED FOR LOCALIZED SEA BREEZES TO FORM
TODAY. THE INTERIOR AND LEEWARD CLOUDS AND SHOWERS SHOULD DIMINISH
WITH SUNSET. VFR AND QUIET SKIES ARE EXPECTED OVER LEEWARD AREAS
TONIGHT.

CLOUDS AND SHOWERS WILL FAVOR WINDWARD AREAS. VFR CONDITIONS ARE
LIKELY INTO EARLY SATURDAY MORNING OVER WINDWARD AREAS. AN AREA OF
ENHANCED MOISTURE...APPROXIMATELY 200 MILES UPSTREAM OF THE SMALLER
ISLANDS...IS FORECAST TO APPROACH THE STATE BY EARLY SATURDAY
MORNING. INCREASED SHOWERS AND CLOUDINESS CAN BE EXPECTED FOR
WINDWARD AREAS. PERIODS OF MVFR AND MOUNTAIN OBSCURATIONS MAY COME
INTO EFFECT AT THAT TIME.

&&

.MARINE...
A RELATIVELY SMALL LONG-PERIOD S SWELL WILL PERSIST THROUGH
SATURDAY...WITH SURF BELOW ADVISORY LEVELS. A LONGER-PERIOD SSW
SWELL EXPECTED SUNDAY WILL PRODUCE ADVISORY-LEVEL SURF ALONG
S FACING SHORES INTO TUESDAY...WITH PEAK OPEN OCEAN SWELL HEIGHTS
NEAR 5 FEET. THIS SWELL MAY CAUSE SURGES IN HARBORS EXPOSED TO THE
S...AND BREAKING WAVES IN AND NEAR S-FACING CHANNEL ENTRANCES.
MARINERS AND BEACHGOERS SHOULD BE ALERT TO THE FACT THAT THIS IS
LIKELY TO BE THE LARGEST S 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. ADDITIONALLY...
THE OAHU SURF DISCUSSION /SRDHFO/ HAS BEEN UPDATED AND CONTAINS MORE
INFO.

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...BIRCHARD
AVIATION...EATON





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