Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 160152
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST MON SEP 15 2014

.SYNOPSIS...
MUGGY CONDITIONS WILL CONTINUE THROUGH MUCH OF THE WEEK. LIGHT TRADE
WINDS WILL RETURN TONIGHT...BUT STILL ALLOW FOR LOCALIZED AFTERNOON
SEA BREEZES AND INTERIOR CLOUDS AND SHOWERS. THE LIGHT TRADES MAY
BREAK DOWN AGAIN LATE IN THE WEEK...LEADING TO CONTINUED MUGGY
CONDITIONS WITH MORE WIDESPREAD SEA BREEZES AND AFTERNOON CLOUDS AND
SHOWERS.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL TROUGH NEARLY STATIONARY
OVER THE STATE. AT THE SURFACE...LOW PRESSURE IS LOCATED FAR TO THE
NORTHEAST...WITH A COLD FRONT EXTENDING SOUTHWESTWARD TOWARD THE
STATE. THE TRAILING END OF THE FRONT/SURFACE TROUGH IS STILL LOCATED
NEAR THE BIG ISLAND...HAVING SLOWED ITS PROGRESS DURING THE DAY.
HIGH PRESSURE IS LOCATED FAR NORTHWEST OF THE STATE. 00Z SOUNDINGS
FROM HILO AND LIHUE SHOW WARMING MID-LEVEL TEMPERATURES WITH A WEAK
INVERSION AND A SLIGHT DECREASE IN MOISTURE DEPTH /MOST PRONOUNCED
AT LIHUE/. PRECIPITABLE WATERS RANGE FROM 1.69 INCHES AT HILO TO
1.35 INCHES AT LIHUE. EARLY AFTERNOON MIMIC TOTAL PRECIPITABLE WATER
IMAGERY IS STILL RUNNING HOTTER THAN THE SOUNDINGS...BUT PICKS UP ON
THE CONCENTRATED BAND NEAR THE BIG ISLAND ASSOCIATED WITH THE
REMNANT FRONT. SOMEWHAT DRIER AIR IS ALSO MOVING TOWARD THE STATE
FROM THE NORTH AND NORTHEAST BEHIND THE FRONT...AS WE ARE STARTING
TO SEE ACROSS KAUAI ALREADY.

RAIN GAGES SHOWED A SIGNIFICANT DECREASE IN RAINFALL ACROSS THE
SMALLER ISLANDS DURING THE AFTERNOON...WITH ONLY A HANDFUL OF GAGES
PICKING UP ANY RAINFALL OVER THE PAST SIX HOURS. A FEW HEAVIER
SHOWERS ARE LOCATED OVER THE BIG ISLAND...WITH THE GREATER MOISTURE
COMBINED WITH DAYTIME HEATING LED TO HEAVIER INTERIOR SHOWERS. THESE
WILL DIMINISH THIS EVENING WITH THE LOSS OF HEATING. DRIER AND MORE
STABLE LOW-LEVEL AIR NEAR KAUAI WILL SPREAD ACROSS THE REST OF THE
STATE THROUGH TONIGHT...LIMITING RAINFALL AMOUNTS. A PATCHY AREA OF
CLOUDS JUST NORTH OF THE COASTAL WATERS IS A SIGN OF ANOTHER POCKET
OF MOISTURE INDICATED BY THE 18Z GFS. THESE CLOUDS HAVE THINNED OUT
DURING THE DAY...BUT MAY BRING SOME MORE SHOWERS TO KAUAI AND OAHU
LATE IN THE NIGHT.

HIGH PRESSURE PASSING NORTH OF THE STATE WILL KEEP A LIGHT
BACKGROUND TRADE WIND FLOW FOR THE NEXT COUPLE DAYS. THE PRESSURE
GRADIENT WILL REMAIN LIGHT ENOUGH THOUGH TO ALLOW LOCALIZED SEA
BREEZES TO FORM. THEREFORE WE WILL CONTINUE TO SEE CLOUD BUILDUPS
AND SOME SHOWERS ACROSS THE INTERIOR OF THE ISLANDS DURING THE
AFTERNOON AND EARLY EVENING. THE LIGHT BACKGROUND TRADES SHOULD BE
ENOUGH TO KEEP SOME CLOUDS FOCUSED ACROSS WINDWARD SECTIONS AT
NIGHT.

LATE IN THE WEEK AND INTO THE WEEKEND...ANOTHER FRONT PASSING NORTH
OF THE STATE SHOULD PUSH THE RIDGE FARTHER SOUTH AND DISRUPT THE
GRADIENT ACROSS THE ISLANDS. THIS WILL LEAD TO ANOTHER PERIOD OF
MORE WIDESPREAD DAYTIME SEA BREEZES AND NIGHTTIME LAND BREEZES. WITH
MORE OF A PURE CONVECTIVE PATTERN...WE SHOULD SEE GREATER CLEARING
AT NIGHT IN ADDITION TO CLOUDS AND SHOWERS DURING THE AFTERNOON.

&&

.AVIATION...
A MOSTLY DRY PATTERN WILL DEVELOP OVERNIGHT AND TUESDAY AS WEAK NE-E
WINDS BUILD OVER THE ISLANDS IN THE WAKE OF A WEAK FRONT...THAT IS
IN THE PROCESS OF DISSIPATING AS IT MOVES SLOWLY S NEAR THE BIG
ISLAND. AIRMET FOR MOUNTAIN OBSCURATION IS POSTED FOR MAUI AND THE
BIG ISLAND...WITH ISOL CLOUD TOPS NEAR FL250 OVER THE BIG ISLAND
SLOPES THIS AFTERNOON. AS DAYTIME HEATING EASES...MOST CLOUDS WILL
GENERALLY CLEAR OVER THE ISLANDS...AND THE EXPECTATION IS THAT THE
AIRMET CAN BE DROPPED EARLY THIS EVENING. THE LIGHT TRADE WINDS WILL
DELIVER ISOL MVFR CIG/VIS IN SHRA TO WINDWARD COASTS AND SLOPES
OVERNIGHT AND EARLY TUESDAY...BUT WEATHER AT THE TERMINALS WILL BE
PREVAILING VFR. LEEWARD CLOUDS WILL INCREASE ONCE AGAIN TOMORROW
LATE MORNING/AFTERNOON...PRODUCING ISOL MVFR VIS/CIG IN SHRA.

&&

.MARINE...
THE CURRENT HIGH SURF ADVISORY FOR SOUTH FACING SHORES HAS BEEN
EXTENDED THROUGH TUESDAY. SURF REPORTS WERE IN THE HIGH-END ADVISORY
RANGE TODAY...WARRANTING AN INCREASE IN HEIGHTS IN THE ADVISORY. THE
SOUTH SWELL WILL GRADUALLY LOWER THROUGH THE NEXT COUPLE DAYS. THE
CURRENT NORTHWEST SWELL HAS SHOWN A GRADUALLY BUILDING HEIGHT AND
DROPPING PERIOD THROUGH THE DAY. WAVEWATCH III GUIDANCE SHOWS THIS
SWELL NEAR ITS PEAK AND SOON TO DIMINISH THROUGH TUESDAY. ADDITIONAL
SMALL NORTH NORTHWEST SWELLS CAN BE EXPECTED DURING THE REST OF THE
WEEK.

WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
LEVELS THROUGH THE FORECAST PERIOD.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR SOUTH FACING SHORES
OF ALL ISLANDS.

&&

$$

DISCUSSION/MARINE...BRAVENDER
AVIATION...BIRCHARD




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