Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 240145
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
345 PM HST WED JUL 23 2014

.SYNOPSIS...
LOCALLY BREEZY TRADE WINDS WILL CONTINUE THROUGH THURSDAY...WITH
TRADE WINDS DIMINISHING SLIGHTLY AS WE HEAD INTO THE WEEKEND. ONLY
BRIEF WINDWARD SHOWERS ARE EXPECTED THE NEXT COUPLE OF DAYS...WITH A
CHANCE THAT WINDWARD SHOWERS WILL INCREASE TOWARDS THE LATER PART OF
THE WEEKEND AND INTO EARLY NEXT WEEK.

&&

.DISCUSSION...
CURRENTLY...MODERATE TO LOCALLY STRONG TRADE WINDS OVER THE ISLANDS
ARE BEING SUPPORTED BY A 1032 MB HIGH CENTERED ABOUT 1550 MILES TO
THE NNE. THE ISLAND ATMOSPHERE HAS BECOME INCREASINGLY DRY AND
STABLE OVER THE PAST 24-36 HOURS...WITH DEW POINTS DOWN ABOUT 8 TO
10 DEGREES...AND AFTERNOON SOUNDINGS INDICATING A STRENGTHENING
INVERSION BASED BETWEEN 6 AND 8 KFT...WITH WARMING IN THE MID- AND
UPPER-LEVELS. LATEST VISIBLE IMAGERY SHOWS A FAIRLY TYPICAL
DISTRIBUTION OF LOW CLOUDS OVER THE ISLANDS AND NEAR SHORE WATERS...
WITH SCATTERED SHOWERY AND STABLE LOW CLOUDS STACKING UP ALONG
WINDWARD COASTS AND SLOPES. A WNW TO ESE ORIENTED BAND OF SHOWERY
LOW CLOUDS ABOUT 100 TO 150 MILES UPWIND OF THE ISLANDS SHOULD FUEL
WINDWARD SHOWERS LATER IN THE EVENING.

THE FORECAST CALLS FOR MID AND UPPER LEVEL RIDGING TO BECOME BETTER
DEVELOPED OVER THE ISLANDS IN THE SHORT TERM...AS DRIER AIR MOVES IN
FROM THE E. THIS WILL LEAD TO A FAIRLY TYPICAL AND BREEZY TRADE WIND
PATTERN INTO FRIDAY...WITH BRIEF WINDWARD SHOWERS FAVORING NIGHTS
AND MORNINGS...AND TYPICAL AFTERNOON CLOUDS AND SHOWERS OVER THE BIG
ISLAND LEEWARD SLOPES. THE TRADE WIND-SUPPLYING HIGH TO THE N IS
FORECAST TO WEAKEN AND SLIDE E LATE THURSDAY INTO FRIDAY...WITH
TRADE WINDS GRADUALLY DIMINISHING IN RESPONSE. ALTHOUGH A WEAKNESS
IN THE RIDGE PREVAILS N OF THE ISLANDS INTO NEXT WEEK...GLOBAL
FORECAST MODELS ARE ANTICIPATING THAT A WEAK TROPICAL SYSTEM WILL
PASS WELL S OF THE ISLANDS THIS WEEKEND AND EARLY NEXT WEEK. WHILE
ANY INCIPIENT SYSTEM IS NOT EXPECTED TO THREATEN THE ISLANDS...IT/S
PRESENCE COULD TIGHTEN THE LOCAL PRESSURE GRADIENT AND PRODUCE
STRONGER TRADE WINDS THAN CURRENTLY FORECAST.

A SLIGHT INCREASE IN TRADE SHOWERS IS POSSIBLE OVER THE WEEKEND AND
EARLY NEXT WEEK AS RIDGING ALOFT GIVES WAY TO WEAK TROUGHING...AND
LOW LEVEL MOISTURE INCREASES FROM THE ESE SUNDAY AND MONDAY. TYPICAL
TRADE WIND WEATHER ON TUESDAY MAY GIVE WAY TO WETTER CONDITIONS
FROM LATE TUESDAY INTO THURSDAY AS MORE TROPICAL MOISTURE
POTENTIALLY ADVECTS IN FROM THE ESE.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT FOR THE TYPICALLY
WINDY WATERS AROUND THE BIG ISLAND AND MAUI DUE TO FRESH TO LOCALLY
STRONG TRADE WINDS. WINDS ARE EXPECTED TO DIMINISH BELOW SCA SPEEDS
FROM FRIDAY INTO SATURDAY...AND THEN INCREASE SLIGHTLY ON SUNDAY AND
MONDAY. THERE/S AN OUTSIDE CHANCE A TROPICAL SYSTEM PASSING WELL S
OF THE ISLANDS KEEPS THE LOCAL GRADIENT TIGHTER THAN CURRENTLY
EXPECTED...WHICH WOULD LEAD TO STRONGER TRADE WINDS.

NO SIGNIFICANT SWELLS ARE EXPECTED THROUGH THE UPCOMING WEEK. SMALL
LONG-PERIOD BACKGROUND SWELL FROM THE SSW AND SHORT-PERIOD SWELL
FROM THE SE REPRESENT THE SWELL SOURCES FROM THE S HEMISPHERE...
WHILE SHORT PERIOD WIND WAVES FROM THE E REPRESENT THE ONLY SOURCE
OF SWELL FROM THE N HEMISPHERE. THE OAHU SURF DISCUSSION /SRDHFO/
HAS BEEN UPDATED AND CONTAINS DETAILS THAN CAN BE LOOSELY APPLIED
STATEWIDE.

&&

.AVIATION...
OVERNIGHT...ISLAND TERMINALS SHOULD REMAIN FAIRLY QUIET AND VFR
CONDITIONS WILL PREVAIL. PASSING SHOWERS EMBEDDED IN THE TRADE WIND
FLOW MAY CARRY BRIEF MVFR CONDITIONS...MAINLY AFFECTING WINDWARD
AND MAUKA AREAS.

MODERATE AND GUSTY TRADE WINDS WILL CONTINUE INTO THURSDAY AND
AIRMET TANGO REMAINS POSTED FOR LOW LEVEL TURB IN THE LEE OF THE
TERRAIN FOR ALL ISLANDS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY THROUGH 6 PM HST THURSDAY FOR THE PAILOLO
AND ALENUIHAHA CHANNELS...MAALAEA BAY AND WATERS SOUTH OF THE BIG
ISLAND.

&&

$$

DISCUSSION/MARINE...BIRCHARD
AVIATION...EATON





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