High Surf in Hawaii, January 1, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST WED DEC 31 2014

.SYNOPSIS...
QUIET...COOL CONDITIONS ARE EXPECTED TO START THE NEW YEAR...AS VERY
DRY AIR STREAMING IN FROM THE NORTH DOMINATES OUR WEATHER. ANOTHER
COLD FRONT SWEEPING DOWN THE ISLAND CHAIN FROM FRIDAY INTO SATURDAY
WILL BRING STRONG AND GUSTY SOUTHWESTERLY WINDS WITH RAINY WEATHER
AND A CHANCE FOR THUNDERSTORMS. THE FRONT IS EXPECTED TO CLEAR THE
BIG ISLAND ON SATURDAY. FAIR AND COOL WEATHER WILL RETURN TO THE
ISLANDS AGAIN FOR THE FIRST WEEKEND OF 2015.

&&

.DISCUSSION...
THE COUNTERCLOCKWISE CIRCULATION AROUND A SURFACE LOW CENTERED NEAR
29N 153W...OR ABOUT 600 MILES NORTH NORTHEAST OF HONOLULU...WILL
MAINTAIN LIGHT TO MODERATE NORTHWEST SURFACE WINDS ACROSS MOST OF
THE FIFTIETH STATE AS WE HEAD INTO THE NEW YEAR. THESE NORTHWESTERLY
WINDS CONTINUE TO ADVECT COOL AND DRY AIR INTO MOST OF THE STATE.
THE MAIN EXCEPTION IS LINGERING MOISTURE NEAR THE EASTERN BIG ISLAND
DUE TO THE FRONT WHICH PASSED ACROSS THE AREA EARLIER THIS WEEK.
NOTE THAT THE BACKGROUND SYNOPTIC FLOW COMBINED WITH LOCAL DRAINAGE
WINDS MAY CARRY MOST OF THE EXCESS SMOKE FROM THE ANNUAL NEW YEARS
EVE FIREWORK EXTRAVAGANZA OUT TO SEA WITHIN AN HOUR OR TWO AFTER
MIDNIGHT HST IN MOST AREAS OF THE STATE.

ALOFT...MID TO UPPER LEVEL TROUGHS ARE PROPAGATING SLOWLY EASTWARD
HIGH ABOVE THE STATE. THESE FEATURES ARE KEEPING ENOUGH INSTABILITY
NEAR THE BIG ISLAND TO ALLOW BROKEN TO OVERCAST LOW CLOUDS AND
ISOLATED SHOWERS TO AFFECT PORTIONS OF THE WINDWARD BIG ISLAND AND
THE ADJACENT COASTAL WATERS THIS EVENING. STRONG MID-TROPOSPHERIC
WINDS ASSOCIATED WITH THE MID-LEVEL TROUGH ARE MAINTAINING GUSTY
WINDS ON THE BIG ISLAND SUMMITS TONIGHT. AS A RESULT...A HIGH WIND
WARNING REMAINS IN EFFECT FOR THE SUMMITS OF MAUNA LOA AND MAUNA
KEA.

OVERALL...LIGHT WINDS AND DRY CONDITIONS ARE EXPECTED TO PRODUCE
RATHER TRANQUIL WEATHER ACROSS THE ALOHA STATE ON NEW YEARS DAY.
HOWEVER...THIS MAY BE THE PROVERBIAL CALM BEFORE THE STORM. NEW MID
TO UPPER LEVEL TROUGHS ARE EXPECTED TO DIG DOWN TOWARD THE ISLANDS
ON FRIDAY. AS A RESULT...A NEW FRONT IS FORECAST TO PUSH DOWN TOWARD
KAUAI...WHICH WILL CAUSE THE LOW-LEVEL FLOW TO STRENGTHEN AND SHIFT
TO A SOUTHWESTERLY DIRECTION. AT THE SAME TIME...THESE WINDS WILL
START TO ADVECT INCREASING LOW-LEVEL MOISTURE INTO THE ISLANDS. THIS
MOISTURE COMBINED WITH THE INSTABILITY DUE TO THE DIGGING TROUGHS
ALOFT WILL ALSO CAUSE INCREASING CLOUDS AND SHOWERS TO DEVELOP OVER
THE PORTIONS OF THE ISLAND CHAIN AHEAD OF THE APPROACHING COLD FRONT
BY EARLY FRIDAY.

UNFORTUNATELY...THERE REMAINS A GREAT DEAL OF UNCERTAINTY DUE TO
INCONSISTENCIES IN THE OUTPUT FROM THE FORECAST MODELS BEYOND EARLY
FRIDAY. THE GFS MODEL CONTINUES TO SUGGEST CYCLOGENESIS MAY OCCUR
ALONG THE FRONT NEAR THE ISLANDS. THIS SCENARIO WOULD LIKELY LEAD TO
STRONG SOUTHWEST WINDS AHEAD OF THE LOW. THESE WINDS...IF THEY DID
DEVELOP...COULD PRODUCE LOCALLY DAMAGING DOWNSLOPE KONA WINDS. IN
ADDITION...STRONG...FAST MOVING THUNDERSTORMS WITH LOCALLY DAMAGING
WIND GUSTS COULD ALSO DEVELOP. HOWEVER...THE ECMWF MODEL SHOWS THE
FRONT WILL SWEEP DOWN ACROSS THE ISLAND CHAIN WITH A WEAK SURFACE
LOW POSSIBLY DEVELOPING NORTH OF THE AREA.

FOR THE CURRENT FORECAST... WE CONTINUE TO FOLLOW AN ECMWF SOLUTION.
AS THE UPPER LEVEL TROUGH PROPAGATES ACROSS THE AREA...THE COLD
FRONT WILL PUSH DOWN ACROSS THE SMALLER ISLANDS FROM FRIDAY
AFTERNOON THROUGH FRIDAY NIGHT...THEN WILL PASS OVER THE BIG ISLAND
SATURDAY. THE FRONT WILL LIKELY BE ACCOMPANIED BY MULTIPLE BANDS OF
SHOWERS AND POSSIBLE THUNDERSTORMS. THE SURFACE WINDS ARE EXPECTED
TO BE STRONG AND GUSTY...ESPECIALLY FRIDAY AND FRIDAY NIGHT. IN
ADDITION...SOME OF THE THUNDERSTORMS THAT DEVELOP MAY ALSO CONTAIN
STRONG WIND GUSTS. AS NOTED IN THE PREVIOUS DISCUSSION...IF THE
LATEST SOLUTIONS OF THE GFS MODEL WERE TO VERIFY...IT IS VERY LIKELY
THAT WIND ADVISORIES AND WARNINGS WOULD BE NEEDED FOR SOME AREAS OF
THE STATE PRONE TO DAMAGING KONA WINDS.

STRONG WINDS ARE ALSO EXPECTED ALOFT OVER THE STATE AS THE MID-LEVEL
TROUGH DIGS OVER THE ISLANDS FRIDAY NIGHT AND SATURDAY. THEREFORE...
EXPECT VERY STRONG WINDS AGAIN ON THE BIG ISLAND SUMMITS. THE HIGH
WIND WARNING WILL LIKELY REMAIN IN EFFECT THROUGH FRIDAY NIGHT...
WITH LOCALIZED WIND GUSTS POSSIBLY EXCEEDING 100 MPH. IN ADDITION TO
THE VERY STRONG WINDS...FROZEN PRECIPITATION...LIKELY SNOW...IS
EXPECTED TO ACCOMPANY THE FRONT ON THE HIGHEST VOLCANIC PEAKS ON THE
BIG ISLAND. IN FACT...BLIZZARD CONDITIONS ARE POSSIBLE AGAIN ON THE
BIG ISLAND SUMMITS LATE FRIDAY NIGHT OR SATURDAY AS THE FRONT
REACHES THE BIG ISLAND.

WEATHER CONDITIONS ARE EXPECTED TO IMPROVE SOON AFTER THE FRONT
MOVES DOWN ACROSS THE STATE. THE COOL...DRY AIR ADVECTED INTO THE
REGION WILL LIKELY PRODUCE RELATIVELY NICE WEATHER ACROSS MOST AREAS
OF THE STATE FROM LATE SATURDAY THROUGH SUNDAY. THE NORTHWEST WINDS
BEHIND THE FRONT WILL LIKELY SHIFT...AND BECOME LIGHT TO MODERATE
DRY TRADES AT THE SURFACE BY EARLY NEXT WEEK AS A SURFACE RIDGE
BUILDS EASTWARD ALONG LATITUDE 25N.

&&

.AVIATION...
RATHER STABLE AIR MASS RESIDES OVER THE ISLANDS WITH THE DECREASING
LOW LEVEL NORTHERLY WINDS. THERE ARE AREAS OF LOW CLOUDS LINGERING
IN THE ISLAND VICINITY...ESPECIALLY OVER THE EASTERN PORTION OF THE
BIG ISLAND AND NORTHEAST WINDWARD MAUI THIS EVENING. THESE CLOUDS
WILL PERSIST ACROSS THE STATE THROUGH EARLY THURSDAY...AND MAY BRING
A SHOWER OR TWO. THE BASE OF THESE CLOUDS IS EXPECTED TO REMAIN HIGH
ENOUGH SUCH THAT VFR CONDITIONS WILL MOSTLY PREVAIL FOR ALL SITES
THROUGH EARLY THURSDAY. THE EXCEPTION WILL BE POSSIBLE SMOKE FROM
THE NEW YEARS FIREWORK CELEBRATION RESULTING IN BRIEF MVFR OR EVEN
IFR VIS CONDITION AT AROUND MIDNIGHT.

AS THE LOW LEVEL WINDS SLOWLY EASE...EXPECT AIRMET TANGO FOR
MODERATE TURBULENCE BELOW 080 FOR AREAS OVER AND IMMEDIATELY TO
THE NORTH AND EAST OF THE MOUNTAINS TO END OVERNIGHT.

&&

.MARINE...
A MIXTURE OF LONG-PERIOD AND SHORT-PERIOD NORTHERLY SWELLS...FROM
BOTH DISTANT AND RELATIVELY CLOSE SOURCES...WILL CONTINUE TO PRODUCE
STORMY SURF ALONG MOST NORTH FACING SHORES. AS A RESULT...A HIGH
SURF ADVISORY REMAINS IN EFFECT FOR ROUGH...ELEVATED SURF ALONG
NORTH FACING SHORES OF MOST ISLANDS THROUGH THURSDAY. IN ADDITION...
THE ELEVATED SEAS WILL PRODUCE HAZARDOUS CONDITIONS MAINLY OVER THE
NORTHERN AND WINDWARD HAWAIIAN COASTAL WATERS. THERE IS A SMALL
CRAFT ADVISORY /SCA/ IN EFFECT FOR THE WATERS EXPOSED TO THE NORTH
SWELLS THROUGH THURSDAY AFTERNOON.

WINDS ARE FORECAST TO REMAIN BELOW SCA CRITERIA THROUGH THURSDAY
NIGHT. HOWEVER...AS THE NEXT COLD FRONT SWEEPS DOWN ACROSS THE AREA
LATE FRIDAY AND SATURDAY...WINDS WILL LIKELY REACH THE SCA CRITERIA
IN SOME OF THE HAWAIIAN COASTAL WATERS. DETAILS OF WHERE THESE WINDS
WILL BE STRONGEST REMAIN UNCERTAIN AT THIS TIME DUE TO THE VARIATION
IN OUTPUT FROM THE DIFFERENT FORECAST MODELS.

IN REGARDS TO UPCOMING WINTER SWELL EVENTS...SHORT- TO MODERATE-
PERIOD NORTH AND NORTHWEST SWELLS WILL CONTINUE TO DOMINATE THE SURF
ALONG OVER MOST OF THE ISLANDS THROUGH FRIDAY. THE WAVE WATCH III
MODEL CURRENTLY SHOWS A LARGE NORTH NORTHWEST SWELL BUILDING FROM
LATE FRIDAY INTO SATURDAY MORNING. THE DETAILS OF THIS SWELL REMAIN
UNCERTAIN AT THIS TIME...SINCE THEY DEPEND ON THE TIMING AND
LOCATION OF THE SURFACE LOW THAT MAY DEVELOP NEAR...OR NORTH...OF
THE ISLANDS. BASED ON THE CURRENT GUIDANCE...EXPECT SURF TO BE NEAR
THE HIGH SURF ADVISORY THRESHOLD OVER MOST NORTH AND WEST FACING
SHORES BY SATURDAY...WITH SLOWLY DECREASING SURF HEIGHTS ON SUNDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST THURSDAY FOR NORTH FACING SHORES
OF NIIHAU...KAUAI...OAHU...MOLOKAI...MAUI...AND THE BIG ISLAND.

HIGH WIND WARNING UNTIL 6 PM HST FRIDAY FOR BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THURSDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-
BIG ISLAND WINDWARD WATERS.

&&

DISCUSSION/MARINE...HOUSTON
AVIATION...HUI