Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 210703
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT SEP 20 2014

.SYNOPSIS...
THE LIGHT WINDS WILL BRING ANOTHER ROUND OF SEA BREEZES AND
AFTERNOON SHOWERS ON SUNDAY...INCLUDING LEEWARD AND INTERIOR AREAS
OF THE ISLANDS. THE TRADES ARE EXPECTED TO STRENGTHEN A LITTLE MONDAY
THROUGH WEDNESDAY WITH SHOWERS BECOMING MORE FOCUSED OVER WINDWARD
AND MOUNTAIN AREAS. A WETTER TRADE WIND PATTERN MAY DEVELOP THURSDAY
AND INTO THE WEEKEND AS MOISTURE ASSOCIATED WITH A WEAKENING FRONT
MOVES CLOSER TO THE ISLAND CHAIN FROM THE NORTH.

&&

.DISCUSSION...
IN GENERAL...HUMID AND MUGGY CONDITIONS CONTINUE ACROSS THE ISLAND
CHAIN AS LIGHT AND VARIABLE WINDS WILL PREVAIL THROUGH AT LEAST
EARLY MON. THIS IS MAINLY DUE TO THE COMBINATION OF A WEAKENING SFC
TROUGH LOCATED AROUND THE KAIWI CHANNEL AND A SFC FRONTAL BOUNDARY
ABOUT 440 MILES N OF KAUAI. THE INFLUENCE OF THESE FEATURES IS
KEEPING PRESSURE GRADIENTS ACROSS THE AREA RELATIVELY WEAK THROUGH
LATE SUN AND INTO EARLY MON.

FOR TONIGHT...RADAR DATA SHOWED SEVERAL AREAS OF ACTIVE SHOWERS WITH
THE MOST RAINFALL BEING OBSERVED DURING THE EARLY EVENING HOURS OVER
THE SE SLOPES OF MAUNA LOA FROM NAALEHU TO WOOD VALLEY...AND
CENTRAL/LEEWARD OAHU FROM WAHIAWA TO MAKAKILO. RAINFALL AMOUNTS
RANGED FROM ONE HALF TO ONE INCH AN HOUR WITH SOME ISOLATED HIGHER
AMOUNTS. THESE SHOWERS WERE PRODUCED BY THE REMNANTS OF EARLIER
AFTERNOON SEA BREEZES...AND SHOULD GRADUALLY DISSIPATE THROUGH THE
REST OF THE EVENING HOURS. HOWEVER...THERE IS STILL PLENTY OF
LINGERING MOISTURE UPSTREAM AND OVER THE ISLAND CHAIN FOR ADDITIONAL
SHOWERS TO DEVELOP THROUGH THE OVERNIGHT HOURS.

MEANWHILE...A WEAK TROPICAL DISTURBANCE IS PASSING JUST TO THE S OF
THE BIG ISLAND....PROVIDING AN ADDITIONAL INCREASE IN DEEP TROPICAL
MOISTURE THAT MAY KEEP FUELING SHOWERS OVER PORTIONS OF THE S HALF
OF THE BIG ISLAND THROUGH SUN. THERE IS ALSO A SLIGHT CHANCE OF
THUNDERSTORMS FOR THE BIG ISLAND SUN AFTERNOON. THE TROPICAL
DISTURBANCE IS EXPECTED TO SLOWLY MIGRATE W DURING THE NEXT COUPLE
OF DAYS. WITH THIS SYNOPTIC SCENARIO IN PLACE...EXPECT ANOTHER ROUND
OF SEA BREEZE INDUCED CLOUDS AND SHOWERS ACROSS THE ISLANDS SUN
AFTERNOON AND EVENING.

FOR EARLY NEXT WEEK...MODELS DEPICT THE PASSAGE OF A WEAK MID LEVEL
TROUGH N OF THE ISLANDS...FOLLOWED BY THE DEVELOPMENT OF A MID-LEVEL
RIDGE. ALSO...A SFC HIGH WILL MOVE FAR N OF THE ALOHA STATE AND
BRING AN INCREASE IN PRESSURE GRADIENTS STARTING MON. THIS WILL
SLIGHTLY STRENGTHEN THE TRADES THROUGH MID WEEK.

MODEL SOLUTIONS SHOW FAIR AGREEMENT IN BRINGING A NEW FRONTAL
BOUNDARY CLOSER TO THE AREA FROM THE N BY WED NIGHT...ENHANCING THE
TRADE SHOWERS OVER WINDWARD AND MOUNTAIN AREAS OF THE SMALLER
ISLANDS IN THE THU-FRI TIMEFRAME...ESPECIALLY AT NIGHT. THE
RETURNING TRADES SHOULD HELP IN COOLING TEMPERATURES A LITTLE NEXT
WEEK...HOWEVER...THE DEW POINTS SHOULD REMAIN HIGH ENOUGH FOR
PERIODS OF MUGGY CONDITIONS EACH AFTERNOON.

&&

.AVIATION...
DIURNALLY DRIVEN SHOWERS FOCUSED OVER ISLAND INTERIORS WILL BECOME
LESS ORGANIZED AND GRADUALLY DIMINISH OVERNIGHT AS SEA BREEZES
TAPER OFF AND WEAK LAND BREEZES DEVELOP. DEEP CONVECTION OVER THE
WATERS SOUTH OF THE BIG ISLAND HOWEVER WILL LIKELY PERSIST OVERNIGHT
DUE TO A WEAK LOW LEVEL DISTURBANCE PASSING JUST SOUTH OF THE STATE.
MVFR CIGS ARE LIKELY IN LOCALLY HEAVY SHOWERS OTHERWISE VFR CONDS
WILL PREVAIL ALL AREAS. SEA BREEZES AND INLAND SHOWERS ARE EXPECTED
TO REDEVELOP ON SUNDAY BUT WITH LESS INTENSITY.

&&

.MARINE...
AN INCREASE IN TRADE WINDS COULD BRING NEAR SMALL CRAFT ADVISORY
CONDITIONS OVER THE TYPICALLY WINDIER WATERS AROUND THE BIG ISLAND
AND MAUI COUNTY BY THE MIDDLE OF NEXT WEEK.

SURF SHOULD REMAIN BELOW ADVISORY CRITERIA ALONG ALL SHORES THROUGH
THE FORECAST PERIOD. SMALL SWELLS WILL PROVIDE SMALL BACKGROUND
SURF ALONG MOST SHORELINES OF ALL THE ISLANDS THROUGH THE WEEKEND.
THEN A COUPLE OF N AND NW SWELLS WILL REACH THE ISLANDS BY WEDNESDAY
AND THURSDAY...WITH A N/NE SWELL POSSIBLE THURSDAY AND FRIDAY. SMALL
LONG-PERIOD S SWELLS WILL KEEP SURF HEIGHTS NEAR OR BELOW SEASONAL
AVERAGES ALONG S FACING SHORES NEXT WEEK.

&&

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

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...BEDAL







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