High Surf in Hawaii, December 10 to 13, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
850 PM HST THU DEC 10 2015

.SYNOPSIS...
GUSTY TRADE WINDS WILL CONTINUE THROUGH FRIDAY. SHOWERS WILL FAVOR
WINDWARD AND MOUNTAIN AREAS WITH A FEW REACHING LEEWARD
LOCATIONS. AN APPROACHING FRONT WILL FORCE WINDS TO BECOME
SOUTHEASTERLY OVER THE WEEKEND...WITH LIGHTER WINDS OVER THE SMALLER
ISLANDS ALLOWING AFTERNOON SEA BREEZES TO DRIVE CLOUD AND
SHOWER FORMATION. MODERATE TRADES WILL RETURN MONDAY.

&&

.DISCUSSION...
BREEZY TRADE WINDS CONTINUE TO PROPEL CLOUDS AND SHOWERS INTO
WINDWARD AREAS...SUPPORTED BY A HIGH PRESSURE CELL PASSING NE OF THE
ISLANDS. A FEW SHOWERS HAVE MOVED INTO LEEWARD LOCATIONS BUT THE
MAJORITY ARE FALLING OVER THE WINDWARD SLOPES. WINDS HAVE APPROACHED
BUT REMAINED BELOW ADVISORY LEVEL SPEEDS OVER HIGHER ELEVATIONS ON
THE BIG ISLAND AND MAUI COUNTY IN PLACES NEAR OR IN THE KOHALA
MOUNTAINS...SADDLE ROAD...AND LANAI. WINDS OVER THE SUMMITS OF THE
BIG ISLAND CONTINUE AT 40 TO 50 MPH...AND THE ONGOING WIND ADVISORY
CONTINUES THROUGH TONIGHT. WINDS OVER THE SUMMIT OF HALEAKALA HAVE
STRENGTHENED TO THE POINT THAT A HIGH WIND WARNING HAS REPLACED THE
ADVISORY THAT WAS IN EFFECT. WINDS ARE EXPECTED TO DIMINISH ON
FRIDAY AS THE SUMMIT-LEVEL FLOW SHIFTS TOWARD THE S.

A FRONT APPROACHING FROM THE W WILL PUSH THE HIGH PRESSURE INTO THE
E PACIFIC OVER THE WEEKEND AND WINDS WILL BECOME ESE OVER MOST OF
THE ISLAND CHAIN. E TRADES WILL PERSIST NEAR THE BIG ISLAND...WHILE
THE SMALLER ISLANDS ARE EXPECTED TO FALL INTO THE WIND SHADOW OF THE
BIG ISLAND. THIS WILL ALLOW LIGHT AND VARIABLE WINDS TO DEVELOP IN
SHADOWED LEEWARD AREAS...WHILE THE WIND AND WEATHER FORECAST FOR
WINDWARD AREAS BECOMES A BIT MORE COMPLEX...WITH THE FORECAST
STRONGLY DEPENDENT ON HOW FAR THE FLOW VEERS TO THE SE.

AFTERNOON SEA BREEZES WITH CLOUDS AND INTERIOR SHOWERS ARE EXPECTED
OVER THE SMALLER ISLANDS WHILE THE BIG ISLAND CONTINUES A WINDWARD
TRADE WIND WEATHER PATTERN. MODELS SHOW A TROUGH MOVING N OF KAUAI
SATURDAY AND SUNDAY WITH AN UPPER LEVEL SHORT WAVE MOVING OVER KAUAI
AND OAHU SATURDAY NIGHT INTO SUNDAY MORNING. AT THIS TIME...THERE IS
A CHANCE KAUAI COULD SEE SOME HEAVY SHOWERS SUNDAY WITH LESS OF A
CHANCE FOR OAHU. THIS FORECAST HAS LOW CONFIDENCE WITH SOME MODELS
BRINGING THE SHORTWAVE ACROSS THE ISLANDS WHILE OTHERS KEEP IT NORTH
OF THE STATE. SO...CURRENT FORECAST MAINTAINS SCATTERED SHOWERS
SUNDAY...BUT HEAVY RAINFALL WORDING HAS BEEN LEFT OUT FOR NOW UNTIL
CONFIDENCE LEVELS INCREASE.

HIGH PRESSURE WILL SLOWLY BUILD BACK NEXT WEEK BRINGING MODERATE
TRADE WINDS AND WINDWARD SHOWERS BACK TO THE ISLANDS.

&&

.AVIATION...
HIGH PRESSURE NORTHEAST OF THE ISLANDS WILL KEEP BREEZY TRADE WINDS
IN PLACE THROUGH FRIDAY. CLOUDS AND SHOWERS WILL FOCUS PRIMARILY
ACROSS MOUNTAIN AND NORTH THRU EAST SECTIONS OF THE ISLANDS...BUT
THE STRONG WINDS WILL ALLOW SOME SHOWERS TO MAKE IT INTO LEEWARD
LOCATIONS AS WELL. SOME BRIEF MVFR CIGS/VSBYS WILL BE POSSIBLE IN
PASSING SHRA ACROSS WINDWARD LOCATIONS INCLUDING PHLI AND PHTO.
ELSEWHERE...PREDOMINANTLY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF
FORECAST PERIOD.

AIRMET SIERRA REMAINS IN EFFECT FOR MOUNTAIN OBSCURATION OVER MAUI
MOLOKAI AND BIG ISLAND...BUT LATEST SATELLITE AND RADAR IMAGES SHOW
ONLY RANDOM SMALL PATCHES OF SHOWERY LOW CLOUDS ARRIVING ON THE
TRADE WIND FLOW...AND THE AIRMET MAY BE CANCELLED OVERNIGHT. AIRMET
TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND DOWNWIND
/SOUTH THRU WEST/ OF THE TERRAIN. CONDITIONS ARE EXPECTED
TO CONTINUE INTO FRIDAY.

&&

.MARINE...
A HIGH SURF ADVISORY CONTINUES FOR N AND W FACING SHORES OF THE
SMALLER ISLANDS THROUGH TONIGHT AS A NW SWELL GRADUALLY DIMINISHES.
A SMALL CRAFT ADVISORY /SCA/ IS IN EFFECT FOR ALL MARINE ZONES
THROUGH TONIGHT...DUE TO A COMBINATION OF WINDS AND SEAS. AS THE
SWELL EASES FRIDAY INTO THE WEEKEND...SO WILL COMBINED SEAS...AT
LEAST OVER SOME OF THE LEEWARD MARINE ZONES. LOCAL WINDS ARE
EXPECTED TO VEER TOWARD THE ESE...WITH LITTLE DECREASE IN SPEED...
OVER THE NEXT 24 HOURS OR SO. THEREFORE MOST WINDWARD MARINE ZONES
WILL CONTINUE WITH SEAS AND WINDS SUFFICIENTLY HIGH TO CONTINUE THE
SCA...AND IT WILL BE EXTENDED ANOTHER 24 HOURS WITH THE UPCOMING
UPDATE TO THE MARINE FORECAST.

ANOTHER NW SWELL IS EXPECTED TO ARRIVE LATE MONDAY AND CONTINUE INTO
WEDNESDAY...WITH LATEST WAVE WATCH GUIDANCE INDICATING THE SWELL
WILL BRING SURF NEAR ADVISORY LEVELS TO EXPOSED N AND W FACING
SHORES. THIS REPRESENTS A DROP IN THE EXPECTED SIZE OF THE SWELL
FROM PREVIOUS ESTIMATES...WITH THE SOURCE LOW STILL EXPECTED TO
CONTAIN HURRICANE FORCE WINDS. HOWEVER...MUCH OF THIS FETCH IS
CURRENTLY ANTICIPATED TO BE AIMED AWAY FROM HAWAII. STILL A FAIR
AMOUNT OF UNCERTAINTY SURROUNDING THE EVENTUAL SIZE OF THIS SWELL.
SURF ALONG E FACING SHORES OF MOST ISLANDS WILL REMAIN ELEVATED AND
CHOPPY THROUGH SATURDAY AS STRONG TRADE WINDS WILL PREVAIL
IMMEDIATELY UPSTREAM OF THE ISLANDS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST FRIDAY FOR NORTH AND WEST FACING
SHORES OF NIIHAU KAUAI OAHU MOLOKAI AND FOR NORTH FACING SHORES OF
MAUI.

WIND ADVISORY UNTIL 6 AM HST FRIDAY FOR BIG ISLAND SUMMITS.

HIGH WIND WARNING UNTIL 6 AM HST FRIDAY FOR HALEAKALA SUMMIT.

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

SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY FOR KAUAI LEEWARD WATERS-
OAHU LEEWARD WATERS-MAUI COUNTY LEEWARD WATERS-MAALAEA BAY.

&&

BIRCHARD