Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 010150
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST TUE SEP 30 2014

.SYNOPSIS...
LIGHT WINDS ACROSS THE STATE COMBINED WITH AN UNSTABLE AIRMASS WILL
RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THIS EVENING.
A MORE STABLE AIRMASS IS EXPECTED FOR THE REST OF THE WEEK...BUT
LIGHT WINDS AND MUGGY CONDITIONS WILL REMAIN.

&&

.DISCUSSION...
A 1027 MB HIGH IS CENTERED FAR NORTHEAST OF THE STATE WITH A WEAK
RIDGE AXIS EXTENDING FROM THIS HIGH TO JUST NORTH OF KAUAI.
MEANWHILE AN UPPER LEVEL TROUGH IS CENTERED NORTHEAST OF THE
BIG ISLAND.  COLD AIR ASSOCIATED WITH THIS UPPER LEVEL TROUGH IS
KEEPING THE AIRMASS VERY UNSTABLE STATEWIDE WITH SHOWERS AND
THUNDERSTORMS...AND LOCALLY HEAVY RAINFALL...POPPING UP OVER THE
INTERIOR SECTIONS OF EACH ISLAND. HIGHEST RAIN AMOUNTS REPORTED SO
FAR THIS AFTERNOON FROM ACROSS THE STATE RANGE FROM 2.5 TO 3.5
INCHES.

THERE REMAINS A THREAT OF SHOWERS AND THUNDERSHOWERS WITH LOCALLY
HEAVY RAINFALL THROUGH THE EVENING HOURS. LIGHT SYNOPTIC SCALE WINDS
WILL ALLOW SEA BREEZES TO DEVELOP AND THESE WILL PROVIDE THE LOW
LEVEL CONVERGENCE NEEDED TO PRODUCE THESE CLOUDS AND SHOWERS. AS THE
SUNSET SETS THIS EVENING...LAND BREEZES WILL DEVELOP AND CLOUDS AND
CHANCES OF SHOWERS DECREASING.

THE OVERALL PATTERN WILL CHANGE LITTLE OVER THE REST OF THE WEEK.
THE UPPER TROUGH WILL WEAKEN...WITH WARMING ALOFT HELPING TO
STABILIZE THE AIRMASS SOME...BUT THERE WILL STILL BE ENOUGH
MOISTURE AND LOW LEVEL INSTABILITY FOR THE AFTERNOON AND EVENING
SHOWERS TO CONTINUE IN AREAS WHERE SEA BREEZES DEVELOP. TEMPERATURES
WILL REMAIN ON THE WARM SIDE IN THE AFTERNOONS...WITH COOL EVENINGS
DUE TO THE LIGHT WINDS.

FOR THE WEEKEND AND EARLY NEXT WEEK...THE MODELS SHOW THE RIDGE
MOVING DIRECTLY OVER THE MAIN HAWAIIAN ISLANDS AS A COLD FRONT
STALLS FAR TO THE NORTH. THIS WILL MAINTAIN WARM AND A BIT MUGGY
CONDITIONS...WITH LIGHT WINDS AND DIURNAL SHOWER CHANCES MAXIMIZING
EACH AFTERNOON AND EVENING.

&&

.AVIATION...
THE SMALLER ISLANDS ARE ACTIVE WITH THUNDERSTORMS THIS AFTERNOON. CB
TOPS ON KAUAI ARE REACHING ABOVE FL450 WITH OCCASIONAL TALLER TOPS.
OVER OAHU...CB TOPS ARE REACHING ABOVE FL350 AND OVER MAUI
COUNTY...CB TOPS TO FL250 WITH OCCASIONAL TOPS TO FL350. ISOLATED
THUNDERSTORMS ARE ALSO MAKING THEIR APPEARANCE ON BIG ISLAND SLOPES.
EXPECT THUNDERSTORMS TO CARRY IFR CONDITIONS. ACTIVITY SHOULD
DIMINISH WITH SUNSET.

OVERNIGHT...SHOWER ACTIVITY WILL FOCUS OVER WINDWARD AND MAUKA
AREAS...AT TIMES CARRYING TEMPO MVFR CONDITIONS. GENTLE BACKGROUND
FLOW WILL ALLOW FOR LOCALIZED LAND BREEZES TO TAKE HOLD.

&&

.MARINE...
THE ONGOING SOUTH SWELL HAS ARRIVED BIGGER THAN EXPECTED AND A HIGH
SURF ADVISORY IS NOW REQUIRED THROUGH WEDNESDAY NIGHT. IN
ADDITION...A NEW NORTHWEST SWELL HAS ARRIVED AND IS EXPECTED TO PEAK
WEDNESDAY BELOW ADVISORY LEVELS. THIS SWELL WILL BE REINFORCED BY A
SMALL NORTHWEST FRIDAY.

&&

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

&&

$$

BRENCHLEY/EATON






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