Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 061919
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST FRI MAR 6 2015

.SYNOPSIS...
BRISK AND COOL NORTHEASTERLY WINDS WILL CONTINUE TO PRODUCE RATHER
WET CONDITIONS ACROSS WINDWARD SLOPES THROUGH TONIGHT. WINDS WILL
DECREASE DURING THE WEEKEND AS A SURFACE RIDGE TO THE NORTH IS
ERODED AND DISPLACED TOWARD THE ISLANDS. DEEPER MOISTURE SOUTH OF
THE BIG ISLAND MAY PUSH FAR ENOUGH NORTH TO INCREASE RAIN AGAIN OVER
THE BIG ISLAND ON SUNDAY OR SUNDAY NIGHT.

&&

.DISCUSSION...
THE ISLANDS LIE WITHIN A TRANSITION ZONE BETWEEN A STRONG 1039 MB
SURFACE HIGH 1500 MILES TO THE NORTHWEST OF KAUAI AND A NEARLY
STATIONARY FRONT ABOUT 400 MILES TO THE NORTHEAST OF THE BIG ISLAND.
MOISTURE POOLED NEAR THE FRONT IS GETTING CAUGHT UP IN THE BRISK LOW
LEVEL NORTHEASTERLY FLOW AND IS BEING TRANSPORTED OVER THE STATE...
ESPECIALLY ACROSS THE EASTERN END OF THE ISLAND CHAIN. THE WETTER
WINDWARD GAUGES PICKED UP AROUND AN INCH ON KAUAI AND OAHU
OVERNIGHT...WHILE QUITE A FEW WINDWARD GAUGES ON MAUI COUNTY AND THE
BIG ISLAND PICKED UP MORE THAN 2 INCHES. LITTLE RAINFALL OCCURRED
ACROSS LEEWARD AREAS.

A BREEZY AND COOL NORTHEASTERLY FLOW WILL CONTINUE TO PRODUCE RATHER
WET CONDITIONS OVER WINDWARD AREAS IN THE SHORT TERM. FORECAST MODELS
SHOW ONLY SLIGHT CHANGES TO THIS SCENARIO THROUGH TONIGHT...WITH THE
MAIN DIFFERENCE BEING A GRADUAL DECREASE IN AVAILABLE LOW LEVEL
MOISTURE. AS A RESULT...EXPECT CONTINUED WET CONDITIONS ACROSS
WINDWARD SLOPES OF ALL ISLANDS INTO TONIGHT...ESPECIALLY ON
MOLOKAI...MAUI...AND THE BIG ISLAND...WITH SOME DECREASE IN RAINFALL
AMOUNTS COMPARED TO LAST NIGHT.

AN INCREASE IN RAINFALL IS POSSIBLE NEAR THE BIG ISLAND BEGINNING
SUNDAY...WHILE ALL ISLANDS WILL SEE A DECREASE IN THE COOL
NORTHEASTERLY WINDS. THE CURRENT LONGWAVE PATTERN FEATURES DEEP
TROUGHING JUST NORTH-NORTHEAST OF THE STATE FLANKED BY DEEP RIDGING.
A SHORTWAVE ALOFT WILL ROTATE THROUGH THE BASE OF THE TROUGH LATE
SUNDAY INTO EARLY MONDAY. THIS WILL WEAKEN THE SURFACE RIDGE
CURRENTLY TO OUR NORTH...LEADING TO A DECREASE IN THE NORTHEAST
WINDS. DEEPER MOISTURE WILL LIKELY BE DRAWN OVER THE BIG ISLAND AND
POSSIBLY AS FAR NORTH AS MAUI...CREATING THE POTENTIAL FOR ANOTHER
ROUND OF WET WEATHER AND SUMMIT SNOWFALL ON THE BIG ISLAND...THOUGH
NOT AS HEAVY OR PERSISTENT AS THE LAST ROUND OF STEADY RAIN. IN
ADDITION...EXPECT INCREASED HIGH CLOUDS STATE-WIDE.

THIS PESKY BAND OF DEEP MOISTURE HANGS AROUND EVEN INTO THE
MIDDLE OF NEXT WEEK. THE 00Z/06 ECMWF STILL EVENTUALLY WANTS TO
BRING HEAVIER SHOWERS UP OVER MAUI AND THE BIG ISLAND...BUT THE
TREND IS LATER...AND FARTHER SOUTH THAN BEFORE AND MORE IN LINE
WITH WHAT THE GFS HAS BEEN PERSISTENTLY SHOWING. THE NORTHERN
ISLANDS SHOULD REMAIN UNDER MODERATE AND RATHER COOL NORTHEASTERLY
LOW LEVEL FLOW WITHIN MAINLY WINDWARD SHOWERS.

ANOTHER PROLONGED EPISODE OF VERY STRONG WINDS FOR THE BIG ISLAND
SUMMITS APPEARS LIKELY AS STRONG LOW PRESSURE IN THE MID-LEVELS
OF THE ATMOSPHERE PRESSES SOUTH TOWARD THE ISLANDS THIS WEEKEND.
IN THE MEANTIME WINDS WILL LIKELY REMAIN NEAR ADVISORY LEVELS FOR
MAUNA LOA AND MAUNA KEA THROUGH ABOUT SATURDAY...THEN RATCHET UP
TO WARNING LEVELS FOR SUNDAY AND BEYOND.

&&

.AVIATION...
BREEZY NORTHEAST WINDS WILL CONTINUE TODAY. AIRMET TANGO FOR LOW
LEVEL TURB OVER AND SOUTH THROUGH WEST OF THE ISLANDS IS POSTED.
THIS WILL LIKELY CONTINUE INTO SATURDAY.

PASSING LOW CLOUDS AND SHOWERS UNDER THE BREEZY NORTHEAST WINDS WILL
BRING PERIODS MVFR CEILINGS AND MTN OBSC OVER WINDWARD SLOPES.
PROLONGED PERIODS OF MVFR CIGS ARE OCCURRING AT PHMK...PHOG...AND
PHTO AS THE MAJORITY OF CLOUDS AND SHOWERS HAVE BEEN FOCUSED OVER
WINDWARD AREAS OF MOLOKAI...MAUI...AND THE BIG ISLAND THIS MORNING.
AIRMET SIERRA FOR MTN OBSC IS POSTED. OTHERWISE...VFR CONDITIONS
SHOULD PREVAIL AT SITES TODAY.

AIRMET TANGO FOR TEMPO LIGHT TO MOD TURB BETWEEN FL250 AND FL400 IS
POSTED AS AN UPPER LEVEL JET SIT OVERHEAD.

&&

.MARINE...
A STRONG...LARGE 1039 MB HIGH ABOUT 1500 MILES NW OF KAUAI IS
KEEPING TRADES MORE NORTHERLY THAN USUAL AND IN THE FRESH TO
LOCALLY STRONG RANGE...WITH SMALL CRAFT ADVISORIES /SCA/ NEEDED
FOR THOSE AREAS WHERE THE NNE WINDS ARE ACCELERATED AROUND ISLAND
TERRAIN. SCA-LEVEL WINDS WILL PERSIST THROUGH FRI NIGHT BUT SHOULD
DROP ON SAT AS A NARROW RIDGE OF HIGH PRESSURE PUSHES S TOWARD THE
ISLANDS. ROUGH SEAS ARE ALSO RUNNING CLOSE TO SCA CRITERIA AS
WELL.

A COMPLEX OF LOW PRESSURE AREAS MILLING AROUND SOUTH OF ALASKA
THE LAST FEW DAYS CREATED A COUPLE OF FETCHES OF NW AND NNW WINDS
SOUTH OF THE ALEUTIANS. THESE WINDS WERE MAINLY BELOW GALE FORCE
BUT STILL ENOUGH TO BRING A COUPLE OF SMALL NW SWELLS TO THE
ISLANDS. THE CURRENT SMALL NW SWELL WILL BE WINDING DOWN AS WE
HEAD INTO THE WEEKEND WHILE THE FORERUNNERS OF ANOTHER ARRIVE ON
FRIDAY.

IN ADDITION...THE GUIDANCE SHOWS ANOTHER COMPLEX LOW DEVELOPING
ABOUT 1100 MILES NNE OF THE ISLANDS ON SATURDAY AND LINGERING
INTO NEXT WEEK. THIS ONE WILL HAVE A FETCH OF NORTHERLIES THAT MAY
REACH GALE FORCE...WHICH WILL SEND A LARGER SWELL THAT WILL LIKELY
REACH THE ISLANDS ABOUT SUNDAY. THE SWELL WILL AGAIN BE RATHER
SHORT FETCH OWING TO THE PROXIMITY OF THE LOW. IT WILL LIKELY BE
SUB-ADVISORY LEVEL FOR NORTH FACING SHORES...BUT SURF HEIGHTS
ALONG E FACING SHORES EXPOSED TO SUCH A SWELL MAY REACH ADVISORY
CRITERIA BY MONDAY AS WELL AS A POSSIBILITY FOR HARBOR SURGES FOR
KAHULUI AND HILO HARBORS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM HST SATURDAY FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SATURDAY FOR KAUAI NORTHWEST
WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-OAHU LEEWARD WATERS-
KAIWI CHANNEL-MAUI COUNTY LEEWARD WATERS-MAALAEA BAY-PAILOLO
CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND
SOUTHEAST WATERS.


&&

$$
DISCUSSION...WROE
MARINE...R BALLARD
AVIATION...EATON










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