Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 061407
AFDHFO

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

.SYNOPSIS...
BRISK...COOL NORTHERLY WINDS WILL PREVAIL THROUGH FRIDAY NIGHT
THANKS TO HIGH PRESSURE FAR TO THE NORTHWEST OF THE ISLANDS.
WINDWARD AND MAUKA AREAS WILL BE RATHER SHOWERY...ESPECIALLY
DURING THE NIGHTS AND MORNINGS. SHOWERS MAY BLOW OVER TO LEEWARD
SECTIONS FROM TIME TO TIME. THE WINDS WILL WEAKEN THIS WEEKEND AS
A RIDGE OF HIGH PRESSURE APPROACHES FROM THE NORTH. 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...
A RATHER SHOWERY NNE FLOW PATTERN CONTINUES THIS MORNING THANKS TO
A RELATIVELY COOL...UNSTABLE BOUNDARY LAYER WHICH IS HELPING TO
ENHANCE OROGRAPHIC LIFT EARLY THIS MORNING. IN FACT...A FEW OF THE
SHOWERS HAVE BEEN BRIEFLY HEAVY. FOR EXAMPLE...THE RAIN GAUGE NEAR
WAIHEE ON MAUI BRIEFLY REPORTED RAINFALL RATES OF NEARLY 2 INCHES
PER HOUR. IT SHOULD CONTINUE TO BE RATHER SHOWERY FOR WINDWARD AND
MAUKA SECTIONS THIS AM...BUT EASING SOME DURING THE DAY BEFORE
THE SHOWERS INCREASE AGAIN TONIGHT. HAVE PAINTED THE FORECAST
FAIRLY WET FOR WINDWARD AND MAUKA SECTIONS THE NEXT COUPLE OF DAYS.

ANOTHER JET STREAK PASSING NORTH OF THE ISLANDS THIS WEEKEND IS
EXPECTED TO INCREASE UPPER LEVEL MOISTURE OVER THE STATE LATER
TODAY...LEADING TO AN INCREASE IN HIGH CLOUDS. THERE IS SOME
DISAGREEMENT AMONG THE MODELS ABOUT HOW MUCH HIGH CLOUDINESS WE
CAN EXPECT...BUT THE CONSENSUS SEEMS TO BE THAT WE WILL SEE BROKEN
TO OVERCAST CIRRUS STARTING LATER TODAY AND LASTING FOR A GOOD
PORTION OF THE WEEKEND...ALTHOUGH SOME SUN SHOULD STILL GET
THROUGH AT TIMES ESPECIALLY FOR THE SMALLER ISLANDS.

THIS JET STREAK WILL ALSO HELP TO PULL THE DEEPER MOISTURE LURKING
SOUTH OF THE BIG ISLAND A LITTLE FARTHER NORTH ONCE AGAIN. THE
MODELS ARE IN PRETTY GOOD AGREEMENT THAT PRECIPITATION WILL
INCREASE NEAR THE BIG ISLAND AGAIN LATER SUNDAY INTO SUNDAY
NIGHT...THOUGH NOT AS HEAVY OR PERSISTENT AS THE LAST ROUND OF
STEADY RAIN. HAVE NOT YET MADE CHANGES TO THE LIKELY POPS WE HAVE
GOING FOR THE SOUTHERN PORTIONS AND KAU DISTRICT ON THE BIG
ISLAND...BUT IT IS POSSIBLE WE MAY NEED TO RAISE POPS A LITTLE
MORE. THERE IS ENOUGH UNCERTAINTY THAT WOULD PREFER TO GET A LOOK
AT LATER RUNS OF THE HIGHER RESOLUTION GUIDANCE...WHICH CURRENTLY
STILL ONLY GOES THROUGH SUNDAY MORNING...BEFORE MAKING CHANGES.

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. WE WILL KEEP AN
EYE ON THIS.

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...
PASSING LOW CLOUDS AND SHOWERS UNDER THE FRESH TRADE WINDS WILL
BRING BRIEF MVFR CEILINGS AND MTN OBSC OVER WINDWARD SLOPES.
OTHERWISE VFR CONDITIONS SHOULD PREVAIL FOR ALL SITES TODAY.

AN AIRMET TANGO FOR MOD LOW LEVEL TURB OVER LEEWARD OF THE SMALLER
ISLANDS WILL LIKELY REMAIN IN EFFECT TODAY DUE TO FRESH TO LOCALLY
STRONG TRADE WINDS.

&&

.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/MARINE...R BALLARD
AVIATION...HUI







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