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Hawaiian Islands Synoptic Discussion and Guidance

034
FXHW60 PHFO 221401
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
401 AM HST WED OCT 22 2014

.SYNOPSIS...
TROPICAL STORM ANA CONTINUES TO MOVE AWAY FROM THE MAIN HAWAIIAN
ISLANDS. EAST SOUTHEAST FLOW WILL PREVAIL OVER MAIN HAWAIIAN
ISLANDS TODAY. A HIGH BUILDING FAR NORTH OF THE AREA WILL BRING
MODERATE TRADE WINDS THURSDAY AND FRIDAY. WINDS WILL WEAKEN AND
SHIFT OUT THE EAST SOUTHEAST AGAIN OVER THE WEEKEND AS A FRONT
APPROACHES FROM THE NORTHWEST.

&&

.DISCUSSION...
TROPICAL STORM ANA...LOCATED SOUTH OF FRENCH FRIGATE SHOALS...CONTINUES
TO MOVE AWAY FROM THE MAIN HAWAIIAN ISLANDS. A BAND OF HIGH CLOUDS
NEARLY SEPARATED FROM ANA WILL MOVE ACROSS KAUAI AND OAHU THIS
MORNING. INFRARED SATELLITE SHOWS LOW LEVEL CLOUD MOTIONS
INDICATIVE OF EAST SOUTHEAST FLOW ACROSS THE MAIN HAWAIIAN
ISLANDS THIS MORNING. THE BIG ISLAND IS PARTLY BLOCKING THE
FLOW ACROSS THE SMALLER ISLANDS...MAKING WINDS RELATIVELY LIGHT.

RADAR INDICATES SCATTERED TO NUMEROUS LIGHT SHOWERS COVERAGE OVER
THE WINDWARD SLOPES AND WATERS WITH A FEW OF THOSE SHOWERS
REACHING UPPER LEEWARD SLOPES OF THE SMALLER ISLANDS. SHOWERS
INCREASED OVERNIGHT DUE TO THE MOISTURE ADVECTING FROM AN OLD
FRONTAL BOUNDARY BRUSHING AGAINST THE WINDWARD AREAS. EARLY
MORNING SOUNDINGS FROM LIHUE AND HILO SHOW A STABLE ATMOSPHERE
WITH RELATIVELY HIGH PRECIPITABLE WATER VALUES OF 1.77 AND 1.54
INCHES RESPECTIVELY...PART OF THE REASON FOR THE LIGHT BUT
NUMEROUS SHOWERS STREAMING IN.

AN EAST TO WEST RIDGE FAR NORTHEAST OF THE BIG ISLAND AND THE
CIRCULATION AROUND TROPICAL STORM ANA WILL COMBINE TO MAINTAIN
GENTLE TO MODERATE EAST SOUTHEAST FLOW OVER THE MAIN ISLANDS
TODAY. WITH THE EAST SOUTHEAST FLOW PARTLY BLOCKED BY THE BIG
ISLAND...WINDS WILL BE LIGHT ENOUGH OVER THE SMALLER ISLANDS FOR
SEA BREEZES TO DOMINATE THIS AFTERNOON AND BRING SOME CLOUDS AND
SHOWERS TO LEEWARD AND INTERIOR AREAS. THE AFTERNOON SHOWERS COULD
BE A BIT MORE ACTIVE GIVEN THE MOISTURE IN PLACE...BUT STABLE
ATMOSPHERIC CONDITIONS SHOULD KEEP THIS RAINFALL ON THE LIGHTER
SIDE. WHILE SHOWERS WILL FOCUS OVER WINDWARD AREAS THIS
MORNING...AS THE SEA BREEZES KICK IN FOR LEEWARD AREAS EXPECT TO
SEE A SHIFT TO MORE LEEWARD AND INTERIOR CLOUDS AND SHOWERS BY
AFTERNOON.

ALTHOUGH WINDS WILL BE RATHER LIGHT AROUND THE SMALLER ISLANDS
TODAY...THE LOW LEVEL FLOW WILL REMAIN STRONGER NEAR THE BIG
ISLAND. THE HAMAKUA COAST AND SOUTH POINT WILL BE SUSCEPTIBLE TO A
BIT STRONGER WINDS DUE TO THE ORIENTATION OF TERRAIN AND WIND FLOW.

THE GLOBAL MODELS ARE IN GOOD AGREEMENT SHOWING A SURFACE HIGH FAR
NORTH NORTHWEST OF THE AREA BUILDING SOUTHEAST ON THURSDAY...STRENGTHENING
THE TRADE WINDS TO MODERATE TO FRESH BREEZES. THE TRADES WILL
PERSIST THROUGH FRIDAY FOCUSING SHOWERS OVER WINDWARD AREAS WITH
MOSTLY DRY WEATHER OVER LEEWARD AREAS.

THE SURFACE RIDGE WILL WEAKEN AND MOVE SOUTH AGAIN OVER THE WEEKEND
AS A FRONT APPROACHES FROM THE NORTHWEST. THE WINDS OVER THE MAIN
ISLANDS WILL WEAKEN AND SHIFT OUT OF THE EAST SOUTHEAST. THAT WIND
FLOW WILL LIKELY BRING SCATTERED NIGHTTIME SHOWERS OVER WINDWARD
AREAS AND SOME CLOUDS AND SHOWERS OVER LEEWARD AREAS IN THE
AFTERNOONS.


&&

.AVIATION...
EARLY THIS MORNING...THE AREA OF ENHANCED MOISTURE ASSOCIATED WITH
AN OLD FRONTAL BOUNDARY HAS MADE ITS WAY INTO THE NORTHERN COASTAL
WATERS AND IS HELPING TO PRODUCE SCATTERED SHOWERS WITH TOPS BETWEEN
8 AND 12 KFT. MVFR CIGS AND VIS ARE LIKELY WITHIN THESE SHOWERS.
EXPECT SOME OF THESE SHOWERS TO PUSH OVER LAND...MAINLY WINDWARD AND
MAUKA AREAS...LATER THIS MORNING AND AFTERNOON...LEADING TO PERIODS
OF MVFR CONDITIONS. AS THIS OCCURS...THERE IS POTENTIAL FOR THE
NEED TO ISSUE AIRMET SIERRA FOR MOUNTAIN OBSCURATION. INTERIOR AREAS
MAY ONCE AGAIN EXPERIENCE AFTERNOON CLOUD BUILD UPS AS THE LIGHT E
TO SE BACKGROUND FLOW WILL ALLOW FOR LOCALIZED SEA BREEZE
DEVELOPMENT. OTHERWISE...VFR CONDITIONS WILL PREVAIL.


&&

.MARINE...
THE CURRENT NORTH SWELL WILL SUBSIDE THROUGH TONIGHT. ANOTHER
SMALL SWELL FROM THE NORTH NORTHWEST ARRIVES THURSDAY AND WILL
CONTINUE THROUGH THE WEEKEND BUT SURF FROM THESE SWELLS WILL
REMAIN BELOW THE ADVISORY LEVELS AT NORTH AND WEST FACING SHORES.
ONLY SMALL SURF IS EXPECTED AT SOUTH AND EAST FACING SHORES.

WINDS AND SEAS WILL REMAIN GENERALLY BELOW SMALL CRAFT ADVISORY LEVELS
THROUGH THE FORECAST PERIOD.


&&

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

&&

$$

DISCUSSION/MARINE...FOSTER
AVIATION...EATON



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