Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 201338
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
338 AM HST WED AUG 20 2014

.SYNOPSIS...
TRADE WIND WEATHER WILL CONTINUE THROUGH THE REST OF THIS
WEEK AND INTO THE WEEKEND...WITH SHOWERS FAVORING WINDWARD AND
MOUNTAIN LOCATIONS. EXPECT ISOLATED SHOWERS TO REACH SOME
LEEWARD AREAS AS WELL. A WESTWARD MOVING AREA OF ENHANCED TROPICAL
MOISTURE MAY BRING AN INCREASE IN SHOWER ACTIVITY ALONG WITH SOME
ISOLATED HEAVIER DOWNPOURS TO PARTS OF THE STATE TONIGHT AND
THURSDAY.

&&

.DISCUSSION...
PASSING TRADE SHOWERS HAVE CONTINUED ACROSS WINDWARD SECTIONS
DURING THE NIGHT...WITH MOST RAINFALL AMOUNTS REMAINING LIGHT.
SURFACE ANALYSIS DEPICTS THE NORTHEAST PACIFIC HIGH IN ITS TYPICAL
SUMMERTIME POSITION ABOUT 1500 MILES NORTHEAST OF HONOLULU...WITH
MODERATE TRADES PREVAILING OVER HAWAII. ALOFT...A WEAK UPPER LOW
IS LIFTING NORTH OF THE STATE...WITH A RIDGE AXIS EXTENDING
WESTWARD ACROSS THE BIG ISLAND. THE 12Z SOUNDINGS SHOW A FAIRLY
WEAK AND HIGH INVERSION BASED AT 7000 TO 8000 FEET...WITH SLIGHTLY
BELOW AVERAGE PWATS OF 1.2 TO 1.3 INCHES. MIMIC-TPW SATELLITE
IMAGERY DEPICTS THE LEADING EDGE OF AN AREA OF DEEPER TROPICAL
MOISTURE (ESTIMATED PWATS OF 1.7 TO 1.9 INCHES) ABOUT 200 MILES
EAST OF THE BIG ISLAND. THERE IS SOME INDICATION IN MSLP ANALYSIS
FIELDS AND LOW CLOUD MOTIONS OF A WEAK INVERTED TROUGH ALONG THE
LEADING EDGE OF THE DEEP MOISTURE.

TYPICAL TRADE WIND WEATHER WILL CONTINUE TODAY...WITH WINDWARD
SHOWERS PRODUCING MOSTLY LIGHT RAINFALL AMOUNTS...AND SCATTERED
SHOWERS POSSIBLE ALONG THE KONA COAST LATE IN THE DAY. FOR TONIGHT
AND THURSDAY...MODELS DIFFER IN THEIR HANDLING OF THE AREA OF
DEEPER MOISTURE CURRENTLY POISED JUST TO OUR EAST. THE GFS BRINGS
THE AREA OF DEEPER MOISTURE THROUGH MOST OF THE STATE...WHILE THE
ECMWF SHUNTS MOST OF THE MOISTURE SOUTH OF THE SMALLER ISLANDS.
FOR THE FORECAST...HAVE CONTINUED TO DEPICT THE HIGHEST POPS
ACROSS THE BIG ISLAND AND WINDWARD MAUI LATE TONIGHT INTO
THURSDAY...WITH SOMEWHAT ENHANCED POPS ACROSS THE REMAINDER OF THE
STATE THROUGH THURSDAY EVENING. WITH THE ADDED MOISTURE AVAILABLE...
ISOLATED HEAVIER DOWNPOURS WILL BE POSSIBLE...BUT THE TRADE FLOW
SHOULD KEEP MOST OF THE SHOWERS MOVING ALONG AND LARGELY PREVENT
EXCESSIVE RAINFALL TOTALS AT ANY SINGLE LOCATION.

THEREAFTER...TYPICAL TRADE WIND WEATHER IS EXPECTED FROM FRIDAY
THROUGH THE WEEKEND. MODEL CONSENSUS FORECASTS THE NORTHEAST
PACIFIC HIGH TO REMAIN STATIC DURING THIS PERIOD. ONCE THE UPPER
LOW INITIALLY NORTH OF THE STATE LIFTS AWAY...RIDGING ALOFT SHOULD
PREVAIL OVER THE STATE THROUGH THE END OF THIS WEEK AND INTO THE
WEEKEND. NEAR TO SLIGHTLY BELOW AVERAGE MOISTURE LEVELS SHOULD
PREVAIL FROM FRIDAY AND SATURDAY...WITH ANOTHER BAND OF SLIGHTLY
HIGHER MOISTURE POSSIBLY MOVING ACROSS THE AREA DURING THE SECOND
HALF OF THE WEEKEND.

TRADES MAY DIMINISH SOMEWHAT ACROSS THE STATE EARLY NEXT WEEK AS
THE NORTHEAST PACIFIC HIGH WEAKENS...BUT AT THIS POINT IT APPEARS
THAT SUFFICIENT TRADE FLOW WILL REMAIN TO PREVENT TRANSITION TO
A SEABREEZE-DOMINATED PATTERN FOR MOST AREAS.

THE TROPICS REMAIN ACTIVE IN THE EAST PACIFIC...BUT LATEST
FORECASTS FROM THE NATIONAL HURRICANE CENTER AND GLOBAL MODELS
CONTINUE TO KEEP ANY TROPICAL SYSTEMS FAR AWAY FROM HAWAII
THROUGH THE FORESEEABLE FUTURE.

&&

.AVIATION...
VFR WILL PREVAIL OVER MOST AREAS THROUGH THE MORNING HOURS.
HOWEVER...BRIEF PERIODS OF MVFR IN LOWER CLOUDS AND LIGHT SHOWERS
WILL AFFECT WINDWARD COASTAL AND MAUKA SECTIONS ACROSS THE STATE.

&&

.MARINE...
THE OVERNIGHT ASCAT PASS MISSED THE HAWAIIAN COASTAL WATERS...
WHILE AN EARLIER LATE TUESDAY MORNING PASS FOUND AREAS OF WINDS
JUST BELOW SMALL CRAFT ADVISORY /SCA/ LEVELS IN THE ALENUIHAHA
CHANNEL AND SOUTH OF THE BIG ISLAND. HAVE DECIDED TO HOLD OFF
FROM POSTING A SCA AT THIS TIME...BUT EXPECT TRADE WINDS TO REMAIN
GENERALLY JUST BELOW ADVISORY LEVELS IN THE WINDIEST AREAS
THROUGH THE REST OF THIS WEEK.

A NEW SSW SWELL WILL ARRIVE TODAY...THEN BUILD TONIGHT AND
THURSDAY...CONTINUING THROUGH FRIDAY. EXPECT THE RESULTING SURF ON
SOUTH FACING SHORES TO INCREASE TODAY....WITH SURF LIKELY NEAR
OR JUST BELOW ADVISORY LEVELS ON THURSDAY. OTHERWISE...SHORT
PERIOD TRADE WIND SWELL WILL CONTINUE ON EAST FACING SHORES...AND
NO SIGNIFICANT NORTHWEST SWELL IS EXPECTED THROUGH THE WEEKEND.

&&

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

&&

$$

DISCUSSION/MARINE...JACOBSON
AVIATION...KINEL





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