High Surf Advisory 7, NWS Honolulu, HI

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
500 AM HST TUE JAN 21 2014

.UPDATE...
MADE A QUICK UPDATE TO THE FORECAST TO ACCOUNT FOR STRENGTHENING
SOUTHWESTERLY WINDS ON THE BIG ISLAND SUMMITS THIS MORNING.
ALSO...ADDED HAZE TODAY FOR PORTIONS OF THE PUNA AND SOUTH HILO
DISTRICTS ON THE BIG ISLAND.

&&

.SYNOPSIS...
A FAST MOVING COLD FRONT APPROACHING KAUAI FROM THE NORTHWEST WILL
CAUSE SOUTHWESTERLY WINDS TO INCREASE OVER THE WESTERN ISLANDS THIS
AFTERNOON...THEN SPREAD DOWN THE ISLAND CHAIN FROM TONIGHT THROUGH
WEDNESDAY. IN ADDITION TO THE GUSTY WINDS...THE FRONT WILL PRODUCE
MOSTLY CLOUDY SKIES WITH BRIEF PERIODS OF LOCALLY HEAVY RAINFALL.
ALSO...A GIANT NORTHWEST SWELL ARRIVING TONIGHT IS EXPECTED TO
PRODUCE WELL ABOVE NORMAL SURF ALONG MOST NORTH AND WEST FACING
SHORES OF THE ALOHA STATE FOR A PROLONGED PERIOD FROM EARLY
WEDNESDAY MORNING INTO THURSDAY.

&&

.DISCUSSION...
AN EAST NORTHEAST TO WEST SOUTHWEST ORIENTED SURFACE RIDGE OVER THE
EASTERN END OF THE STATE CONTINUES TO DISRUPT THE PRESSURE GRADIENT
ACROSS THE ISLANDS EARLY THIS MORNING. WATER VAPOR IMAGERY SHOWS
UPPER LEVEL RIDGING ALONG WITH SIGNIFICANT UPPER LEVEL SUBSIDENCE
HIGH ABOVE MOST OF THE ISLANDS. AS A RESULT OF THESE SYSTEMS AT THE
SURFACE AND ALOFT...DRY AND STABLE CONDITIONS WITH LIGHT WINDS WILL
LIKELY PREVAIL ACROSS MOST OF THE FIFTIETH STATE THIS MORNING.

THE CLOUD BAND ASSOCIATED WITH A RELATIVELY STRONG COLD FRONT IS
EVIDENT IN SATELLITE IMAGERY ABOUT 375 MILES NORTHWEST OF LIHUE
EARLY THIS MORNING. THIS LEADING EDGE IS MOVING TOWARDS THE EAST
SOUTHEAST AT 25 MPH...AND THE FORECAST MODELS INDICATE THIS FRONT
WILL SLOW DOWN AS IT APPROACHES KAUAI. THE FRONT IS EXPECTED TO
REACH KAUAI COUNTY LATER TONIGHT...OAHU EARLY WEDNESDAY MORNING...
MAUI COUNTY LATE WEDNESDAY MORNING...AND THE BIG ISLAND WEDNESDAY
AFTERNOON. THE FRONT IS FORECAST TO PUSH EAST OF THE BIG ISLAND BY
MIDNIGHT HST THURSDAY...WHERE IT SHOULD DISSIPATE OVER THE OPEN
OCEAN EAST OF THE BIG ISLAND BY LATE THURSDAY OR FRIDAY.

AS THE FRONT APPROACHES AND THE PRESSURE GRADIENT TIGHTENS OVER THE
WESTERN END OF THE STATE...STRENGTHENING SOUTHWEST WINDS WILL FIRST
OCCUR IN THE VICINITY OF KAUAI COUNTY..AND THEN SPREAD TOWARD OAHU
AND MAUI COUNTY. THE STRONGEST WINDS ARE EXPECTED ON KAUAI AND
OAHU...WHERE WINDS WILL BE IN THE 20 TO 25 MPH RANGE. WINDS IN SOME
AREAS OF KAUAI AND OAHU COULD APPROACH THE WIND ADVISORY CRITERIA.
NOTE THAT THE NORTHEAST FACING AREAS OF THESE ISLANDS WILL BE
PARTICULARLY SUSCEPTIBLE TO STRONG LOCALIZED WIND GUSTS AS THESE
SOUTHWEST WINDS ACCELERATE DOWN THE SLOPES OF THE HIGHER TERRAIN. ON
OAHU...THIS CAN OCCUR OVER AREAS DOWNWIND OF THE WAIANAE AND KOOLAU
MOUNTAIN RANGES. IN THE PAST...THESE STRONG WINDS HAVE LEAD TO
LOCALIZED PROPERTY DAMAGE AND SPOTTY POWER OUTAGES. THEREFORE...WE
HAVE INCLUDED A MENTION OF GUSTS OF UP TO 45 MPH...JUST BELOW WIND
ADVISORY CRITERIA...IN SELECT AREAS ON KAUAI AND OAHU FOR TONIGHT
AND WEDNESDAY.

ONCE THE FRONT PASSES...THE WINDS WILL SHIFT TO A WESTERLY
DIRECTION...AND THEN BECOME NORTHWESTERLY. THE BIG ISLAND SUMMITS
WILL LIKELY SEE STRONG WINDS FROM THIS EVENING INTO WEDNESDAY...WITH
WIND ADVISORY...OR POSSIBLY HIGH WIND WARNING...CONDITIONS
DEVELOPING OVER THE HIGHER TERRAIN DURING THIS TIME.

BASED ON THE LATEST GUIDANCE...THE MAIN UPPER LEVEL SUPPORT FOR THIS
FRONT MOVING DOWN THE ISLAND CHAIN WILL REMAIN NORTH OF THE ISLANDS.
THEREFORE...WE DO NOT CURRENTLY HAVE THUNDERSTORMS OR SIGNIFICANT
HIGHER ELEVATION WINTER WEATHER CONDITIONS IN THE FORECAST.
HOWEVER...BRIEF HEAVY DOWNPOURS MAY OCCUR AHEAD OF AND ALONG THE
FRONT...SO THE POTENTIAL FOR LOCALLY HEAVY RAINFALL IS BEING
INCLUDED IN THE FORECAST.

A WEAK SURFACE HIGH IS FORECAST TO FILL IN WEST OF THE FRONT...WHILE
AN UPPER LEVEL RIDGE IS REINFORCED ABOVE THE STATE. AS A RESULT...A
DRY AND STABLE AIR MASS WILL DEVELOP BEHIND THE FRONT AS THE WINDS
BEGIN TO TAPER OFF WEDNESDAY EVENING. WITH THE CLOSE PROXIMITY OF
SURFACE HIGH PRESSURE TO THE ISLANDS...SURFACE WINDS ARE EXPECTED TO
REMAIN RELATIVELY LIGHT ACROSS MOST OF THE ISLANDS FROM THURSDAY
INTO THIS WEEKEND.

THE WEATHER FROM SUNDAY INTO EARLY NEXT WEEK REMAINS QUESTIONABLE
DUE TO UNCERTAINTIES IN THE FORECAST MODELS. THE LATEST RUNS OF THE
MODELS APPEAR TO INDICATE A SHEAR LINE WILL MOVE DOWN ACROSS THE
ISLANDS FROM THE NORTH NORTHWEST BY LATE MONDAY. THERE ALSO APPEAR
TO BE STRONG NORTHEASTERLY WINDS ASSOCIATED WITH THE ARRIVAL OF THIS
FEATURE EARLY NEXT WEEK. THE LONG-RANGE FORECAST NOW HAS WET WEATHER
WITH GUSTY NORTHEASTERLY WINDS FROM LATE MONDAY INTO TUESDAY...BUT
THIS IS SUBJECT TO CHANGE IF THE MODELS BEGIN TO SWAY IN A NEW
DIRECTION LATER TODAY OR WEDNESDAY.

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL ACROSS THE HAWAIIAN ISLANDS TODAY. BUT A
FRONT WILL BEGIN TO MOVE ACROSS THE ISLAND CHAIN THIS EVENING AND
EXIT THE STATE WEDNESDAY NIGHT. THE FRONT HAS SLOWED FROM 30KT TO
NEAR 25KT SINCE LAST EVENING. CURRENTLY EXPECT THE FRONT TO REACH
LIHUE AROUND 221200Z...HONOLULU AROUND 221600Z AND HILO AROUND
230200Z. EXACT TIMING REMAINS TO BE SEEN AS FRONT MAY CONTINUE TO
SLOW OR ACCELERATE UNEXPECTEDLY.

LIGHT WINDS STILL PREVAIL OVER MOST AREAS WITH A WEAK RIDGE STILL
OVER THE STATE. THE RIDGE WILL CONTINUE TO GRADUALLY SHIFT EASTWARD
AS THE FRONT APPROACHES. THE LIGHT WINDS WILL EVENTUALLY BE REPLACE
BY INCREASING SW WINDS AHEAD OF THE FRONT TODAY. THE FRONTAL CLOUD
BAND WILL BRING MOSTLY MVFR AND SOME IFR CONDITIONS IN THE WAY OF
LOWER CEILINGS AND SHOWERS WHICH WILL LIMIT VISIBILITIES. NORTHERLY
WINDS AND CLEARING WILL SOON FOLLOW BEHIND THE FRONT AND ITS CLOUD
BAND.

&&

.MARINE...
A GIANT NORTHWEST SWELL WAS GENERATED FROM A LOW WITH HURRICANE
FORCE WINDS FAR TO THE NORTHWEST OF THE ALOHA STATE. THIS SWELL WILL
RESULT IN HIGH SURF WARNING CONDITIONS ALONG MOST NORTH AND WEST
FACING SHORES BEGINNING LATE TONIGHT AND EARLY WEDNESDAY MORNING.
THE LATEST OUTPUT FROM THE WAVEWATCH III MODEL INDICATES THE
NORTHWEST SWELL WILL PEAK EARLY WEDNESDAY MORNING...WITH SURF
HEIGHTS OF 40 TO 50 FEET ALONG NORTH FACING SHORES. THE LARGEST
WAVES ARE EXPECTED TO BREAK OVER THE OUTER REEFS AND IN DEEP WATER
BAYS...WITH CONSIDERABLE WAVE RUN UP EXPECTED ALONG THE BEACHES.
THIS NORTHWEST SWELL WILL BE LONG-LIVED...SO WARNING LEVEL SURF IS
EXPECTED TO CONTINUE INTO THURSDAY. THIS MEANS THERE WILL LIKELY BE
ELEVATED SURF...WAVE RUN UP AND COASTAL INUNDATION FOR MULTIPLE TIDE
CYCLES...SO PROPERTY OWNERS AND OTHER INTERESTS ALONG THE NORTH AND
WEST FACING SHORES EXPOSED TO THIS LARGE SWELL...INCLUDING THE
LEEWARD BIG ISLAND...NEED TO PREPARE FOR AN EXTENDED ONSLAUGHT OF
WELL ABOVE NORMAL WAVES.

A FAST MOVING FRONT WILL APPROACH KAUAI LATER TODAY AND TONIGHT.
SOUTHWEST WINDS WILL STRENGTHEN AHEAD OF AND ALONG THE FRONT AS IT
PASSES OVER THE STATE. THE WINDS WILL BEGIN TO INCREASE OVER KAUAI
COUNTY THIS AFTERNOON...AND THEN SPREAD DOWN THE ISLAND CHAIN FROM
TONIGHT INTO WEDNESDAY. THESE STRONG WINDS REQUIRED THE ISSUANCE OF
A SMALL CRAFT ADVISORY /SCA/ FOR THE KAUAI NORTHWEST WATERS AND
WINDWARD WATERS STARTING LATER THIS MORNING. THE ARRIVAL OF THE
LARGE NORTHWEST SWELL WILL ALSO RESULT IN SMALL CRAFT ADVISORY /SCA/
CONDITIONS SPREADING ACROSS MOST OF THE HAWAIIAN COASTAL WATERS DUE
TO COMBINED SEAS OF 10 FEET OR GREATER. THEREFORE...A SCA HAS ALSO
BEEN ISSUED FOR ADDITIONAL COASTAL WATERS AND CHANNELS ADJACENT TO
KAUAI...OAHU AND MAUI COUNTY STARTING THIS EVENING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 PM HST WEDNESDAY
FOR THE KAUAI NORTHWEST WATERS AND WINDWARD WATERS.

SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM HST WEDNESDAY
FOR THE KAUAI LEEWARD WATERS...OAHU WINDWARD AND LEEWARD WATERS...
MAUI COUNTY WINDWARD WATERS...AND FOR THE KAUAI AND KAIWI CHANNELS.

&&

DISCUSSION/MARINE...HOUSTON
AVIATION...FUJII