Heavy Rain in Hawaii, June 6, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
335 PM HST SAT JUN 6 2015

.SYNOPSIS...
LIGHT TRADE WINDS WILL GRADUALLY STRENGTHEN FROM LATE SUNDAY INTO
MONDAY...WITH MODERATE TRADE WINDS THEN PERSISTING THROUGH THE
UPCOMING WEEK. WITH THE LIGHT WINDS...SKIES WILL CLEAR AFTER SUNSET
TONIGHT...AND AFTERNOON CLOUDS AND SHOWERS WILL FORM OVER LEEWARD
AND INTERIOR AREAS AGAIN ON SUNDAY. ONCE THE TRADE WINDS RETURN ON
MONDAY...CLOUDS AND SHOWERS WILL FAVOR WINDWARD AREAS...MAINLY
DURING NIGHTS AND MORNINGS. CLOUDS AND SHOWERS WILL ALSO DEVELOP
OVER THE KONA SLOPES ON THE BIG ISLAND EACH AFTERNOON.

&&

.DISCUSSION...
THE CURRENT WEATHER PATTERN HAS CHANGED LITTLE SINCE THIS MORNING...
WITH A LIGHT TO MODERATE EASTERLY TRADE WIND FLOW NEAR AND S OF THE
BIG ISLAND...WEAK ESE FLOW OVER MAUI COUNTY AND OAHU WINDWARD
WATERS...AND NEARLY CALM LARGE-SCALE WINDS NEAR KAUAI. A SURFACE
RIDGE IS ANALYZED TO BE IN POSITION JUST N OF KAUAI...EXTENDING SW
FROM A HIGH FAR NE OF THE AREA. THE RIDGE REMAINS SUPPRESSED
SOUTHWARD FROM ITS CLIMATOLOGICAL POSITION DUE TO A SOMEWHAT
UNSEASONABLE FRONT THAT HAS ITS LEADING EDGE ABOUT 425 MILES NW OF
KAUAI. WITH THE LIGHT WINDS...AS EXPECTED...MORNING SUNSHINE GAVE
WAY TO SEA-BREEZE-DRIVEN INTERIOR CLOUDS AND SHOWERS. DESPITE
THIS...MANY COASTAL AREAS MANAGED TO REMAIN RATHER SUNNY THROUGH
THE DAY.

CLOUDS AND SHOWERS WILL DIMINISH THROUGH THE EVENING HOURS AS
ISLAND-SCALE LAND BREEZES GRADUALLY DEVELOP OVER THE SMALLER
ISLANDS. ISLAND SKIES WILL CLEAR WELL BEFORE MIDNIGHT...AND REMAIN
THAT WAY THROUGH MID-MORNING ON SUNDAY. WITH LITTLE IN THE WAY OF
MOISTURE LOCATED E OF THE ISLANDS...ONLY A SLIGHT CHANCE OF SHOWERS
IS FORECAST FOR WINDWARD BIG ISLAND OVERNIGHT.

LATEST GUIDANCE INDICATES THE FRONT WILL STALL ABOUT 375 MILES NW
OF KAUAI LATER TONIGHT INTO SUNDAY. THE FRONT IS THEN FORECAST TO
GRADUALLY DISSIPATE INTO TUESDAY AS THE HIGH TO THE NE ALSO
DISSIPATES. A NEW HIGH NOW NW OF THE ISLANDS WILL BUILD N OF THE
AREA SUNDAY AND MONDAY...SUPPORTING A SLOWLY STRENGTHENING TRADE
WIND FLOW. THIS HIGH WILL SUPPORT MODERATE TRADE WINDS THROUGH NEXT
WEEK AS IT MOVES E. TRADE WIND SPEEDS WILL BEGIN TO REBOUND ON
SUNDAY...BUT THE FLOW LOOKS TO BE LIGHT ENOUGH FOR ONE MORE DAY OF
AFTERNOON INTERIOR/LEEWARD CLOUDS AND A FEW SHOWERS. WITH THE
ATMOSPHERE REMAINING DRY AND SOMEWHAT STABLE...SHOWER COVERAGE...
LIKE TODAY...SHOULD BE LIMITED.

TRADE WINDS WILL CONTINUE TO BUILD INTO MONDAY...AND THE WEEKEND
CONVECTIVE PATTERN OF AFTERNOON LEEWARD/MAUKA CLOUDS AND SHOWERS
WILL SWITCH BACK TO A TRADE WIND PATTERN WHERE WINDWARD CLOUDS AND
SHOWERS FAVOR NIGHTS AND MORNINGS. ONE CAVEAT TO THE OTHERWISE
BENIGN TRADE WIND WEATHER PATTERN INVOLVES A DEVELOPING CUT OFF LOW
NE OF THE ISLANDS EARLY NEXT WEEK. THIS LOW IS FORECAST TO DEVELOP
ON MONDAY...LINGER FOR SEVERAL DAYS ABOUT 500 MILES NE OF THE
ISLANDS...AND THEN EJECT TO THE NE BY THE END OF THE WEEK. THE
PRESENCE OF THIS LOW...AND AN ASSOCIATED TROUGH ALOFT THAT WILL
EXTEND SW OVER THE ISLANDS...WILL WEAKEN THE SUBSIDENCE INVERSION
AND MAY LEAD TO INCREASED TRADE WIND SHOWERS...AND AFTERNOON KONA
SLOPE SHOWERS. LATEST GFS GUIDANCE IS HONING IN ON AN AREA OF
MOISTURE MOVING E TO W ACROSS THE ISLAND CHAIN MONDAY NIGHT AND
TUESDAY...WITH ECMWF PAINTING A SIMILAR PICTURE. HAVE INCREASED
WINDWARD POPS FOR THIS TIME FRAME...BUT OTHERWISE THE LOW ALOFT IS
NOT EXPECTED TO SIGNIFICANTLY IMPACT ISLAND WEATHER WITH ITS
ASSOCIATED COLD POOL ALOFT REMAINING WELL NE OF THE ISLANDS.

&&

.AVIATION...
LIGHT WINDS OVER THE LEEWARD AREAS WILL ALLOW FOR DOWNSLOPE FLOW
TONIGHT WHILE WINDWARD AREAS MAINTAIN LIGHT TO MODERATE TRADE WINDS.
MAINLY VFR CONDITIONS WILL PREVAIL TONIGHT WITH ISOL MVFR POSSIBLE
OVER WINDWARD SLOPES. NO AIRMETS ARE EXPECTED.

&&

.MARINE...
A SMALL NW SWELL PEAKING TODAY AND LOWER SUNDAY...WITH PEAK SURF
HEIGHTS WELL BELOW ADVISORY LEVELS. SWELLS ARRIVING FROM THE S AND
SSW WILL KEEP SEASONABLY-SIZED SURF ALONG S FACING SHORES INTO
EARLY NEXT WEEK...WITH RESULTANT SURF BELOW ADVISORY LEVELS. A SMALL
BUT RELATIVELY LONG PERIOD E SWELL GENERATED BY FORMER HURRICANE
ANDRES IN THE E PACIFIC APPEARS TO HAVE PEAKED...AND WILL GRADUALLY
DIMINISH INTO MONDAY. THE COLLABORATIVE NEARSHORE SWELL AND WIND
FORECAST /SRDHFO/ WAS UPDATED FRIDAY AND CONTAINS DETAILS.

WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS FOR
THE NEXT COUPLE OF DAYS...WITH WINDS POTENTIALLY BECOMING STRONG
ENOUGH TO WARRANT A SMALL CRAFT ADVISORY FOR THE WINDY ZONES AROUND
MAUI AND THE BIG ISLAND NEXT WEEK.

&&

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

&&

DISCUSSION/MARINE...BIRCHARD
AVIATION...MORRISON