Heavy Rain in Hawaii, September 10, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
408 PM HST WED SEP 10 2014

.SYNOPSIS...
GENTLE TO LOCALLY MODERATE TRADE WINDS WILL PERSIST INTO SATURDAY.
THE TRADES WILL DELIVER BRIEF SHOWERS TO WINDWARD AREAS...BUT WILL
ALSO BE LIGHT ENOUGH TO ALLOW AFTERNOON SEA BREEZES TO PRODUCE
CLOUDS AND ISOLATED SHOWERS OVER LEEWARD AREAS. WINDS WILL BECOME
EVEN LIGHTER OVER THE WEEKEND AND EARLY NEXT WEEK...LEADING TO A
LAND AND SEA BREEZE PATTERN. IN THIS REGIME...CLEAR SKIES AT NIGHT
AND IN THE MORNING WILL GIVE WAY TO AFTERNOON AND EVENING
CLOUDINESS...WITH A FEW POP-UP SHOWERS OVER INTERIOR AREAS.

&&

.DISCUSSION...
THE GENTLE TO LOCALLY MODERATE TRADE WIND FLOW CURRENTLY IN PLACE
WILL CONTINUE INTO SATURDAY...AS A WEAK RIDGE OF HIGH PRESSURE
REMAINS SITS SEVERAL HUNDRED MILES N OF THE ISLANDS. THE TRADE
WIND FLOW WILL CONTINUE TO BE PARTIALLY OVERPOWERED BY LAND BREEZES
LATE AT NIGHT AND BY AFTERNOON SEA BREEZES...MAINLY OVER LEEWARD
AREAS. IN THIS HYBRID TRADE WIND AND SEA BREEZE PATTERN...EXPECT
CLOUDS AND SHOWERS TO FAVOR WINDWARD AREAS NIGHTS AND MORNINGS...
WITH CLOUDS AND SPOTTY SHOWERS DEVELOPING OVER AND JUST W OF LEEWARD
TERRAIN EACH AFTERNOON. LIMITED MOISTURE AND MODERATE STABILITY
WILL LIMIT THE VIGOR OF THESE SHOWERS OVER THE NEXT DAY. THERE IS
THE POTENTIAL FOR A SLIGHT INCREASE THURSDAY NIGHT AND FRIDAY AS
AN AREA OF MOISTURE UPSTREAM ARRIVES IN THE WEAK TRADE FLOW. HIGH
CLOUDS MAY INCREASE NEAR KAUAI AND OAHU ON FRIDAY AND SATURDAY AS
A NEW TROUGH ALOFT SHARPENS JUST N OF KAUAI...BUT MODEL TRENDS
INDICATE THAT HIGH LEVEL MOISTURE / CLOUD COVER WILL BE LIMITED.

TRADE WINDS WILL DIMINISH FURTHER DURING THE WEEKEND...BECOMING LIGHT
AND VARIABLE THROUGH EARLY NEXT WEEK...AS A COUPLE OF DISSIPATING
FRONTS APPROACH THE ISLANDS FROM THE N...AND THE SURFACE RIDGE MOVES
OVER / NEAR THE ISLANDS. MODEL GUIDANCE CONTINUES TO FEATURE SOME
SLIGHT DIFFERENCES IN THE TIMING...WITH THE ECMWF DEPICTING WINDS
DIMINISHING MORE QUICKLY...WHILE THE GFS IS A LITTLE SLOWER. EITHER
WAY...WINDS WILL BECOME SUFFICIENTLY LIGHT FOR A LAND AND SEA BREEZE
PATTERN TO TAKE OVER SATURDAY. THIS REGIME WILL FEATURE NIGHTTIME
LAND BREEZES LEADING TO MOSTLY CLEAR NIGHTS AND MORNINGS...WITH
LATE MORNING/AFTERNOON SEA BREEZES BRINGING INTERIOR CLOUDS AND A
FEW SHOWERS. ALTHOUGH MOISTURE ASSOCIATED WITH THE DISSIPATING
FRONTAL BOUNDARIES MAY BE IN PLACE NEAR KAUAI AND OAHU...IT IS
EXPECTED TO RATHER SHALLOW.

WINDS WILL REMAIN LIGHT THROUGH EARLY NEXT WEEK...WITH LIGHT TRADES
POTENTIALLY RETURNING AROUND THE MIDDLE OF THE WEEK AS THE FRONTS
GRADUALLY WASH OUT AND THE RIDGE TO THE N STRENGTHENS SLIGHTLY.

&&

.AVIATION...
A GENTLE TO LOCALLY MODERATE TRADE WIND FLOW WILL CONTINUE TO BRING
ISOL MVFR CIGS AND SHRA TO WINDWARD SLOPES. AFTERNOON CLOUD BUILD
UPS AND ISOL MVFR CIGS AND VIS IN SHRA WILL DIMINISH RAPIDLY AROUND
SUNSET...WITH A REPEAT EXPECTED AGAIN THURSDAY AFTERNOON. NO
AIRMETS.

&&

.MARINE...
WINDS AND SEAS ACROSS THE COASTAL WATERS WILL REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLDS INTO NEXT WEEK...AS LIGHT TO MODERATE
TRADE WINDS BECOME EVEN LIGHTER OVER THE WEEKEND.

THE CURRENT NW SWELL WILL GRADUALLY DIMINISH THROUGH FRIDAY.
ANOTHER SMALL TO MODERATE NW SWELL DUE SUNDAY AND MONDAY WILL BE
GENERATED BY THE EXTRATROPICAL LOW THAT DEVELOPS FROM FORMER W
PACIFIC TROPICAL CYCLONE FENGSHEN...WITH PEAK OPEN OCEAN SWELL
HEIGHTS NEAR 4 FEET.

SURF ALONG S FACING SHORES WILL REMAIN ON THE SMALL SIDE THROUGH
FRIDAY...NEAR OR BELOW SEASONAL AVERAGES. LONG PERIOD FORERUNNERS
FROM A NEW S SWELL ARRIVING FRIDAY NIGHT ARE ASSOCIATED WITH A
POWERFUL LOW THAT PASSED SOUTHEAST OF NEW ZEALAND A COUPLE OF DAYS
AGO. SATELLITE WIND DATA INDICATED HURRICANE FORCE WINDS WITH THE
LOW. ALTHOUGH THE BULK OF THE FETCH ASSOCIATED WITH THIS LOW WAS
AIMED E OF THE ISLANDS...THESE WINDS SUPPORT THE NOTION THAT THE
SWELL WILL HAVE WAVE PERIODS BETWEEN 20 AND 25 SECONDS WHEN IT FIRST
ARRIVES. AS THIS SWELL FILLS IN THROUGH THE WEEKEND...IT IS EXPECTED
TO PRODUCE SURF AROUND THE S SHORE ADVISORY LEVEL SATURDAY THROUGH
MONDAY.

&&

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

&&

DISCUSSION/MARINE...FOSTER
AVIATION...WROE