Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 211334
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST SUN SEP 21 2014

.SYNOPSIS...
LIGHT WINDS WILL ALLOW FOR SEA BREEZES TO RETURN THIS AFTERNOON AND
BRING ANOTHER ROUND OF CLOUDS AND SHOWERS...ESPECIALLY OVER LEEWARD
AND INTERIOR AREAS. 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 STARTING LATE WEDNESDAY AND CONTINUING THROUGH THE WEEKEND
AS MOISTURE ASSOCIATED WITH A WEAKENING FRONT MOVES CLOSER TO THE
ISLAND CHAIN FROM THE NORTH.

&&

.DISCUSSION...
THE INFLUENCE OF A NEARLY STATIONARY WEAKENING SFC TROUGH NEAR OAHU
AND A SFC FRONTAL BOUNDARY ABOUT 400 MILES N OF KAUAI IS KEEPING
PRESSURE GRADIENTS ACROSS THE AREA RELATIVELY WEAK TODAY AND THROUGH
EARLY MON. WINDS WILL REMAIN LIGHT AND VARIABLE...ALLOWING FOR HUMID
AND MUGGY CONDITIONS TO CONTINUE TODAY AND TONIGHT,

A WEAK TROPICAL DISTURBANCE IS MOVING JUST S/SW OF THE BIG
ISLAND....AND WILL PROVIDE AN ADDITIONAL SOURCE OF DEEP TROPICAL
MOISTURE FOR SHOWERS TO DEVELOP ACROSS PORTIONS OF THE S HALF
OF THE BIG ISLAND THROUGH THIS EVENING. THERE IS ALSO A SLIGHT
CHANCE OF THUNDERSTORMS FOR THE BIG ISLAND THIS AFTERNOON AS SEA
BREEZE CIRCULATIONS BECOME MORE INTENSE AND PUSH INLAND. THE
TROPICAL DISTURBANCE WILL CONTINUE TO SLOWLY MIGRATE W DURING THE
NEXT COUPLE OF DAYS.

FOR THE FIRST HALF OF THE 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 TO THE N OF THE
ALOHA STATE AND BRING AN INCREASE IN PRESSURE GRADIENTS STARTING
MON. THIS WILL SLIGHTLY STRENGTHEN THE TRADES THROUGH THE MIDDLE OF
THE WORK WEEK.

LATEST GLOBAL MODEL SOLUTIONS...MAINLY GFS AND ECMWF...SHOW FAIR
AGREEMENT IN BRINGING A NEW FRONTAL BOUNDARY CLOSER TO THE AREA
FROM THE N BY WED NIGHT. THIS SCENARIO WILL HELP IN ENHANCING THE
TRADE SHOWERS...ESPECIALLY OVER WINDWARD AND MOUNTAIN AREAS OF THE
SMALLER ISLANDS IN THE LATE WED TO FRI TIMEFRAME...WITH BEST CHANCES
OF RAINFALL DURING THE NIGHTTIME HOURS.

THE RETURNING TRADES WILL ALSO HELP IN COOLING TEMPERATURES A LITTLE
NEXT WEEK...HOWEVER...THE DEW POINTS SHOULD REMAIN HIGH ENOUGH FOR
PERIODS OF MUGGY CONDITIONS TO RETURN EACH AFTERNOON.

&&

.AVIATION...
MOSTLY CLEAR SKIES ACROSS THE SMALLER ISLANDS THIS MORNING WILL
PERSIST THROUGH MIDDAY. MID LEVEL CLOUDINESS AND ISOLATED SHOWERS
ACROSS THE BIG ISLAND WILL BECOME MORE WIDESPREAD AS WILL LOCALLY
HEAVY SHOWERS OFFSHORE W AND SE OF THE BIG ISLAND. AFTERNOON SEA
BREEZES WILL ACT TO ORGANIZE DIURNAL CONVECTION ACROSS ISLAND
INTERIORS. BOTH SEA BREEZES AND INTERIOR SHOWERS WILL TAPER OFF
AFTER SUNSET. ISOL MVFR POSSIBLE IN SHOWERS OTHERWISE PREVAILING VFR
ALL AREAS.

ALSO...A WEAK DISTURBANCE PASSING JUST SSW OF THE STATE COULD
TRIGGER A FEW TSTMS THIS AFTERNOON OR EARLY EVENING ON THE BIG
ISLAND OR IN ITS SOUTHERN OR SOUTHWESTERN ADJACENT WATERS.

&&

.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 MID 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 TODAY.
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 DURING THE REST OF THE WEEK.

&&

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

&&

$$

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






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