High Surf Advisory 69, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1036 AM HST FRI DEC 25 2015

.SYNOPSIS...
GUSTY TRADE WINDS ARE EXPECTED THROUGH THE HOLIDAY WEEKEND AS A NEW
SURFACE HIGH PASSES NORTH OF THE STATE. THE BLUSTERY TRADES ARE
EXPECTED TO BE ACCOMPANY BY AN ABUNDANT LOW CLOUDS AND SHOWERS.
THIS WET AND WINDY TRADE WEATHER PATTERN WILL FOCUS MOST OF THE
RAINFALL OVER WINDWARD AND MAUKA AREAS...BUT THE STRONG TRADES
WILL LIKELY CARRY SOME SHOWERS OVER TO THE LEEWARD SECTIONS OF
THE SMALLER ISLANDS.

&&

.DISCUSSION...
HIGH PRESSURE WILL CONTINUE TO DOMINATE THE WEATHER AROUND THE
MAIN HAWAIIAN ISLANDS FOR THE NEXT SEVERAL DAYS. THE CURRENT HIGH
PRESSURE CELL IS LOCATED FAR NE OF THE MAIN ISLANDS. A NEW MODERATELY
STRONG HIGH OF A 1031 MB CURRENTLY LOCATED BY THE DATELINE AND 32N.
IT IS FORECAST TO RACE EASTWARD AT 35 TO 40 MPH...PASSING NORTH OF
THE MAIN HAWAIIAN ISLANDS BY 880 MILES SATURDAY AFTERNOON WHILE
HOLDING STEADY AT 1031 MB. THE HIGH SLOWS DOWN TO 25 TO 30 MPH
THEREAFTER WITH A MORE NORTHEAST TRACK.

SO THE TRADES WILL BE RAMPING UP DURING THE 24 HOURS AROUND THE
ISLANDS. SATELLITE DERIVED WINDS DETECTED 30 KT SPEEDS IN THE
WIND SENSITIVE ALENUIHAHA CHANNEL OVERNIGHT...AND WON/T TAKE MUCH
FOR THE WINDS TO REACH GALE FORCE THERE IN THE CHANNEL TONIGHT.
GALE FORCE TRADES MAY OCCUR IN ONE OR TWO MORE CHANNELS TOO BUT
WILL GO WITH ONE FOR THE TIME BEING. OVER LAND...WE ARE
CONTEMPLATING A WIND ADVISORY FOR THE SENSITIVE AREAS OF NORTHERN
BIG ISLAND AND MAY BE LANAI PERHAPS STARTING AT 6 PM HST THIS
EVENING. WE WILL BE WATCHING CLOSELY FOR ADVISORY LEVEL WINDS
REACHING OTHER AREAS OF THE STATE...ALTHOUGH THE THOUGHT IS THIS
EVENT WILL BE LIMITED AND NOT AS WIDESPREAD AS TO THE LAST WIND
EVENT ABOUT A WEEK AGO.

THE STRONG TRADES WILL BEGIN EASING OFF SUNDAY NIGHT AS THE HIGH
PULLS FURTHER AWAY FROM THE ISLANDS. THERE IS A FRONT ABOUT 375
MILES NORTHWEST OF KAUAI NOW...BUT IT IS RAPIDLY FALLING APART
AND SHOULD NOT BE A FACTOR TO THE FORECAST.

THE STABILITY OF THE AIR MASS OVER THE ISLANDS ALREADY UNSTABLE
AS THE MORNING SOUNDS FROM LIH AND ITO SHOWS NO LOW LEVEL INVERSION.
ALSO...THE LATEST SATELLITE INFRARED SHOT SHOWS A POSSIBLE TOWERING
CUMULUS CLOUDS OF AROUND 20K FEET WITH THE BLOB OF MOISTURE IN THE
KAUAI CHANNEL.

LOW CLOUD COVERAGE SHOWS TWO AREAS OF CLOUDS AND SHOWERS. ONE IS
IN THE KAUAI CHANNEL AND SHOULD BE AFFECTING THE GARDEN ISLE FOR
A GOOD PART OF THIS AFTERNOON. AS NOTED ABOVE...TCU/S ARE NOTED
UPWIND OF THE CHANNEL ALREADY.

THE SECOND AREA OF MOISTURE HAS JUST REACHED WINDWARD MAUI AND
SHOULD CONTINUE TO SPREAD WESTWARD WITH THE TRADES LIKELY GRAZING
MOLOKAI THIS AFTERNOON. MOLOKAI IS CURRENTLY IN A DRY SLOT. THE
TRADE SHOWERS HAVE EASED OFF ON OAHU BUT MORE IS ON THE WAY...
ALTHOUGH NOT AS SHOWERY AS EARLIER THIS MORNING. WINDWARD BIG
ISLAND WILL CONTINUE TO BE PEPPERED WITH SCATTERED SHOWERS INTO
THIS AFTERNOON AND EVENING. THE SHOWERS IN THE CAPTAIN COOK AREA
OF THE BIG ISLAND HAVE ENDED...LEAVING SOME BROKEN LOW CLOUDS
BEHIND THIS 9 AM HOUR. SOME SCATTERED SHOWERS MAY REFORM INLAND
LATER THIS AFTERNOON. OVERNIGHT SHOWERS ALONG THE COAST IS
POSSIBLE TONIGHT.

A MID LEVEL DISTURBANCE IS FORECAST TO CUT THROUGH THE ISLANDS FROM
THE NORTHWEST TONIGHT...BRINGING SLIGHTLY COLDER TEMPS TO AT OR
BELOW FREEZING FOR THE BIG ISLAND SUMMITS. THERE IS ALREADY AMPLE
MOISTURE UP THERE AT 40 TO 50 PERCENT RH...AND MAY RISE WITH ANY
PASSING ENHANCED TRADE SHOWER. SO ICY ROADS MAY BE AN ISSUE THAT
WILL TRIGGER AND WINTER WEATHER ADVISORY STARTING TONIGHT.

THEN BOTH THE ECMWF AND GFS MODELS POINT TO THE SHORTWAVE TROUGH
PINCHING OF A MID LEVEL LOW JUST SOUTHWEST OF KAUAI BY SATURDAY
EVENING. THIS FEATURE WILL ADD THE POTENTIAL FOR SNOW FOR THE BIG
ISLAND SUMMITS ON SUNDAY AND SUNDAY NIGHT.

THE STRONG TRADES ARE EXPECTED TO BEGIN EASING OFF SUNDAY EVENING
AND TURN LIGHT BY TUESDAY WITH A FRONT PASSING NORTH OF THE
ISLANDS.

&&

.AVIATION...

TRADE WINDS WILL CONTINUE TO RAMP UP TODAY AS A HIGH NW OF THE AREA
MOVES E. AIRMET TANGO FOR LOW LEVEL TURB IS POSTED FOR AREAS OVER
AND IMMEDIATELY S THROUGH W OF THE MOUNTAINS. VAD WIND PROFILES FROM
THE VARIOUS RADARS AND A MORNING AMDAR REPORT OUT OF PHNL SHOW
PERSISTENT 20 KT WITH A FEW 25 KT WINDS THROUGHOUT THE LAYER.

CLOUDS AND SHOWERS WILL FAVOR WINDWARD AND MAUKA AREAS WITH THE
INCREASING TRADE WINDS PUSHING SOME SHOWERS TO LEEWARD AREAS.
INCREASED MOISTURE AROUND THE STATE WILL HELP FUEL SHOWERS...AND
SOME MAY CARRY PERIODS OF MVFR CONDITIONS. AIRMET SIERRA FOR
MOUNTAIN OBSC IS POSTED OVER N THROUGH E SECTIONS ON KAUAI...OAHU...
MAUI...AND THE BIG ISLAND. THE BIG ISLAND WINDWARD AREA HAS CLEARED
THIS MORNING...HOWEVER SATELLITE SHOWS PATCHES OF SHOWERY CLOUDS
JUST UP STREAM. THEREFORE...AIRMET SIERRA ON THE BIG ISLAND WILL
REMAIN POSTED IN ANTICIPATION OF THE APPROACHING SHOWERS.
&&

.MARINE...
IN RELATION TO THE DISCUSSION NOTED ABOVE...WE HAVE GONE AHEAD IN
ISSUING A GALE WARNING FOR THE ALENUIHAHA CHANNEL. WE HAVE ALSO
EXPANDED THE SMALL CRAFT ADVISORY TO COVER THE REMAINING COASTAL
MARINE ZONES. THIS IS ALL GOOD TO 6 AM HST SUNDAY WITH THE
POTENTIAL FOR AN EXTENSION.

WE WILL ALSO BE TAKING A LOOK AT A HIGH SURF ADVISORY FOR THE EAST
FACING SHORES OVER THE WEEKEND DUE TO THE STRENGTHENING TRADES. WE
MAY NOT ISSUE IT NOW BUT TONIGHT OR TOMORROW.

A NORTHWEST SWELL IS EXPECTED TO ARRIVE SUNDAY AND PEAK SUNDAY
NIGHT. THE SURF MAY REACH THE HIGH SURF ADVISORY CRITERIA ALONG
MOST NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS. THIS
SWELL WILL GRADUALLY DECLINE MONDAY. ALSO...AN OUT OF SEASON
SOUTH SWELL IS FORECAST TO PRODUCE A BUMP IN SURF ALONG SOUTH
FACING SHORES OF THE ISLAND CHAIN THIS WEEKEND.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
GALE WARNING IS IN EFFECT UNTIL 6 AM HST SUNDAY FOR THE ALENUIHAHA
CHANNEL.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY FOR ALL REMAINING
COASTAL WATERS.

&&

DISCUSSION/MARINE...LAU
AVIATION...EATON