Heavy Rain in Hawaii, May 31, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT MAY 30 2015

.SYNOPSIS...
LIGHT TO MODERATE TRADES WILL CONTINUE THROUGH EARLY NEXT WEEK. SEA
BREEZES ARE LIKELY TO RETURN ON SUNDAY AND MONDAY WITH CLOUDS AND
SHOWERS DEVELOPING OVER LEEWARD AREAS IN THE AFTERNOON AND EVENING
HOURS. THE TRADE WINDS WILL ALSO KEEP BRINGING SHOWERS TO WINDWARD
AND MOUNTAIN AREAS...ESPECIALLY AT NIGHT AND IN THE MORNING HOURS.

&&

.DISCUSSION...
PREVAILING MODERATE TRADES CONTINUE TO BRING SHOWERS OVER WINDWARD
AND MOUNTAIN AREAS OF THE SMALLER ISLANDS...WITH POSSIBLE LOCALIZED
DOWNPOURS. RADAR AND SATELLITE DATA HAVE BEEN SHOWING THE MOST
ACTIVE SHOWERS ANCHORED OVER THE CENTRAL AND EASTERN PORTIONS OF THE
KOOLAU MOUNTAINS IN OAHU...AND SPREADING INTO INTERIOR AREAS AROUND
WAHIAWA AND MILILANI AT TIMES. RADAR ESTIMATES SHOW ACCUMULATIONS
BETWEEN HALF TO ONE INCH PER HOUR ON THE AVERAGE...BUT BRIEF
LOCALIZED HIGHER AMOUNTS ARE CERTAINLY POSSIBLE THROUGH THE REST OF
THE EVENING AND THE OVERNIGHT HOURS. ADDITIONAL SHOWERS CAN BE
OBSERVED LINGERING OVER THE WINDWARD SLOPES OF HALEAKALA IN MAUI.
RADAR DATA ALSO SHOW A COUPLE OF LINES OF SHOWERS REMAINING NEARLY
STATIONARY JUST OFFSHORE OF THE NE COASTLINE OF THE BIG ISLAND.

THE OOZ SOUNDINGS FROM HILO AND LIHUE SHOW PWATS INCREASING INTO THE
1.3 TO 1.4 INCHES RANGE. THIS IS IN PART DUE TO THE PRESENCE OF
INCREASED MOISTURE ASSOCIATED WITH THE REMNANTS OF A FORMER COLD
FRONT BOUNDARY LINGERING ABOUT 350 MILES E OF THE BIG ISLAND.
ELEVATED WEAK INVERSIONS AROUND 9 TO 12 THOUSAND FEET ALSO SUGGEST
GOOD POTENTIAL FOR SHOWERS TO MOVE BEYOND THE MOUNTAINS AND REACH
LEEWARD AREAS AT TIMES. THE W EDGE OF THE REMNANT BOUNDARY IS MARKED
BY A 120 MILE WIDE BAND OF CLOUDS ORIENTED FROM E TO W NOW LOCATED
ACROSS THE W HALF OF THE ISLAND CHAIN...MAINLY AROUND KAUAI AND JUST
N OF OAHU. THIS FEATURE IS EXPECTED TO LINGER OVER THE AREA AND
CONTINUE TO SUPPORT SHOWER ACTIVITY TONIGHT AND INTO SUN.

THE BAND OF CLOUDS AND ENHANCED MOISTURE WILL LIKELY PUSH S...RATHER
SLOWLY...AND BECOME STATIONARY AROUND MAUI AND THE BIG ISLAND BY
MON AS SFC HIGH PRESSURE FAR NW OF THE STATE BEGINS MOVING CLOSER TO
THE AREA. MEANWHILE...MODELS CONTINUE TO SUGGEST THE DEVELOPMENT OF
A DEEPENING UPPER LEVEL TROUGH SEVERAL HUNDRED MILES N OF THE
ISLANDS....WITH AN ACCOMPANYING CLOSED LOW MIGRATING E DURING THE
FIRST HALF OF THE WORK WEEK. IN RESPONSE...MODEL SOLUTIONS ARE
TRYING TO GENERATE A SFC TROUGH...WHILE ENERGIZING THE
AFOREMENTIONED STALLED FRONTAL REMNANT AS THE TROUGH/LOW COMPLEX
MOVES TO THE N OF THE ISLANDS. THIS SYNOPTIC SCENARIO WILL KEEP GOOD
POTENTIAL FOR ENHANCED SHOWER ACTIVITY ACROSS THE MAIN HAWAIIAN
ISLANDS IN THE TUE-THU TIMEFRAME. THIS SHOULD ALSO KEEP A LIGHT
TRADE WIND REGIME IN PLACE THROUGH MID WEEK. THEREFORE...EXPECT A
COMBINATION OF ENHANCED WINDWARD/MOUNTAIN SHOWERS AND AFTERNOON SEA
BREEZE-INDUCED SHOWERS OVER LEEWARD AREAS EACH DAY.

THE BAND OF CLOUDS AND MOISTURE SEEMS TO FINALLY BEGIN DISSIPATING
TOWARDS THE END OF THE WORK WEEK AS THE UPPER LOW/TROUGH COMPLEX
MOVES FURTHER AWAY FROM THE AREA. A MORE ROBUST TRADE WIND FLOW
SHOULD GRADUALLY RETURN NEXT WEEKEND AS THE HIGH PRESSURE FAR N
OF THE ISLANDS STRENGTHENS IN THE WAKE OF THE TROUGH.

&&

.AVIATION...
LIGHT TO MODERATE TRADES WILL PREVAIL OVER THE AREA THIS EVENING AND
OVERNIGHT. RIDING ON THE TRADE FLOW...REMNANT SHOWERY LOW CLOUDS
FROM AN OLD FRONT WILL MAINLY AFFECT WINDWARD AND MAUKA SECTIONS
ACROSS THE STATE...BRINGING TEMPO MVFR CONDITIONS IN LOWER CEILINGS
AND VISIBILITIES. VFR WILL PREVAIL OTHERWISE.

BECAUSE OF THE CONDITIONS DESCRIBED ABOVE...AN AIRMET FOR MOUNTAIN
OBSCURATION HAS BEEN POSTED FOR NORTH THRU EAST SECTIONS ON MOST
ISLES.

&&

.MARINE...
A LONG-PERIOD SOUTH SOUTHWEST SWELL CONTINUES  TO BUILD AT BUOYS
SOUTH OF THE HAWAIIAN ISLANDS...WITH BUOYS 51002...51003 AND
51004...AS WELL AS THE BARBERS POINT BUOY...ALL DETECTING INCREASING
ENERGY WITHIN THE 19 TO 23 SECOND BANDS. INCONSISTENT SMALL TO
MODERATE SURF CONTINUES ALONG SOUTH FACING SHORES AT DUSK THIS
EVENING. HOWEVER...SURF HEIGHTS ARE EXPECTED TO BUILD OVERNIGHT...
REACHING THE HIGH SURF CRITERIA BY DAYBREAK SUNDAY MORNING. BASED ON
THE LATEST GUIDANCE FROM THE WAVE WATCH III MODEL...THIS SWELL IS
EXPECTED TO BUILD THROUGH SUNDAY...PEAK MONDAY...AND THEN GRADUALLY
DIMINISH TUESDAY AND WEDNESDAY. NOTE THAT WITH OPEN OCEAN SWELL
HEIGHTS EXPECTED TO PEAK NEAR 5 FEET...THIS SWELL MAY CAUSE MODERATE
SURGES IN HARBORS EXPOSED TO THE SOUTH. IN ADDITION...LARGE BREAKING
WAVES MAY OCCUR IN AND NEAR SOUTH FACING CHANNEL ENTRANCES. MARINERS
AND BEACHGOERS SHOULD BE ALERT TO THE FACT THAT THIS IS EXPECTED TO
BE THE LARGEST SOUTHERN HEMISPHERE SWELL SO FAR THIS SEASON.
ALSO...EXTREME TIDAL CHANGES WILL ALSO LEAD TO LOCALLY STRONG
CURRENTS IN THE SURF ZONE. A MARINE WEATHER STATEMENT HAS BEEN
ISSUED TO DESCRIBE THESE POTENTIAL HAZARDS FOR MARINERS AND
BEACHGOERS.

OTHERWISE...SMALL AND RELATIVELY SHORT-PERIOD NORTHWEST SWELLS WILL
ARRIVE INTO EARLY NEXT WEEK. THESE SWELLS WILL SUPPORT SMALL SURF
ALONG MOST NORTH FACING SHORES. FINALLY...BASED ON THE LATEST
FORECAST...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW THE SMALL
CRAFT ADVISORY /SCA/ CRITERIA INTO THE MIDDLE OF NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM 6 AM SUNDAY TO 6 PM HST MONDAY FOR SOUTH
FACING SHORES OF ALL ISLANDS.

&&

SYNOPSIS/DISCUSSION...REYNES
MARINE...HOUSTON
AVIATION...KINEL