High Wind and Heavy Rain in Hawaii, January 2 to 3, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1019 AM HST FRI JAN 2 2015

.SYNOPSIS...
A STRONG COLD FRONT WILL SWEEP RAPIDLY DOWN THE ISLAND CHAIN
TONIGHT AND EARLY SATURDAY BRINGING BANDS OF SHOWERS...LOCALLY
STRONG KONA WINDS...AND A CHANCE OF THUNDERSTORMS. WINDS WILL
SHIFT TO NORTHWEST AND SHOWERS WILL DIMINISH AFTER THE FRONT
PUSHES THROUGH. COOL AND DRY WEATHER IS EXPECTED BEHIND THE FRONT
ON SUNDAY...WITH A RELATIVELY DRY TRADE WIND PATTERN RESUMING
EARLY NEXT WEEK.

&&

.DISCUSSION...
AS ONE FORECASTER HERE MENTIONED THIS MORNING...THIS SEEMS TO BE
THE PROVERBIAL CALM BEFORE THE STORM. LOW PRESSURE NEAR FRENCH
FRIGATE SHOALS WILL CONTINUE TO PUSH E AND GRADUALLY DEEPEN...
DRAGGING AN ACTIVE COLD FRONT WITH IT. THE FRONT WILL HAVE STRONG
SUPPORT IN THE MID AND UPPER LEVELS IN THE FORM OF A DIGGING
TROUGH THAT WILL HELP PROPEL THE FRONT THROUGH THE ISLANDS FAIRLY
QUICKLY... STARTING NEAR KAUAI THIS EVENING AND PASSING THE BIG
ISLAND EARLY SAT. THERE IS STRONG DIVERGENCE ALOFT...AND THERE
WILL BE STRONG LOW LEVEL CONVERGENCE ALONG THE BOUNDARY...SO AM
EXPECTING TO SEE AN ACTIVE SQUALL LINE/QLCS SWEEP RAPIDLY DOWN
THE CHAIN.

SINCE THIS FRONT IS FOLLOWING SO QUICKLY ON THE HEELS OF THE LAST
ONE...THE MOISTURE RETURN HAS NOT BEEN IDEAL...AND THIS WILL LIMIT
THE AMOUNT OF INSTABILITY AVAILABLE FOR THUNDERSTORMS. THE MODELS
ARE SHOWING FAIRLY MODEST CAPE OF ABOUT 500-900 J/KG WHICH FROM
PAST EVENTS WOULD SUGGEST SOME THUNDERSTORMS ALONG THE SQUALL LINE
BUT NOT AS EXTENSIVE AS THEY MIGHT BE OTHERWISE. ANY OF THE MORE
ACTIVE CONVECTION COULD HELP TO MIX DOWN STRONGER WINDS FROM
ALOFT LEADING TO LOCALIZED DAMAGING WINDS IN ADDITION TO THE
DOWNSLOPE ACCELERATION OF THE WINDS ON THE NORMAL-WINDWARD SIDES
OF THE ISLANDS AND THROUGH THE SADDLES AND HEADLANDS WHICH COULD
ALSO CAUSE SOME PROBLEMS.

ALTHOUGH SHOWERS COULD BE INTENSE BRIEFLY ALONG THE FRONT...THE
PRESENT THINKING IS THAT THE FAST MOTION OF THE FRONT SHOULD
GREATLY LIMIT THE POTENTIAL FOR FLASH FLOODING...ALTHOUGH WE CAN/T
COMPLETELY RULE IT OUT. AS THE FRONTAL BAND GETS TO THE BIG ISLAND
LATE TONIGHT OR EARLY SATURDAY...EXPECTING TO SEE BLIZZARD
CONDITIONS THERE AND HAVE ISSUED A BLIZZARD WARNING FOR AREAS
ABOVE 11000 FEET TO GO ALONG WITH THE PILE OF OTHER HEADLINES
THAT ARE CURRENTLY OUT.

MOST OF THE GUIDANCE CLEARS THE FRONT PAST THE BIG ISLAND SAT
MORNING. WEATHER CONDITIONS WILL IMPROVE FROM WEST TO EAST ON SAT
AS A DRIER AIRMASS BUILDS INTO THE STATE ON NW WINDS BEHIND THE
FRONT. DRY AND COOL NORTHERLY FLOW WILL PREVAIL ON SUNDAY.
RELATIVELY DRY TRADE WIND CONDITIONS SHOULD RESUME ON MONDAY AND
PREVAIL THROUGH THE MIDDLE OF NEXT WEEK...AS HIGH PRESSURE BUILDS
SLOWLY EASTWARD TO THE NORTH OF THE STATE. A WEAK FRONT
APPROACHING FROM THE NORTHWEST MAY ALLOW THE TRADES TO WEAKEN AND
VEER SLIGHTLY BY NEXT THURSDAY OR FRIDAY...BUT NO MAJOR WEATHER
CHANGES ARE EXPECTED.

&&

.AVIATION...
SATELLITE LOOPS SHOW A FRONT NW OF KAUAI MOVING ESE AROUND 25 KT.
STRONG SW WINDS WILL CONTINUE OVER THE AREA AHEAD OF THE FRONT SO
AIRMET TANGO REMAINS IN EFFECT FOR BOTH STRONG SURFACE WINDS AND
TURBULENCE TO THE LEE..NE...OF THE MOUNTAINS. WEATHER WILL REMAIN
GENERALLY VFR AHEAD OF THE FRONT BUT LOCALIZED MVFR IS POSSIBLE...
MAINLY FOR SW SLOPES...IN PREFRONTAL CONVERGENCE LINES.

A BAND OF SHOWERY CLOUDS ALONG THE FRONT WILL BRING MVFR/LOCAL IFR
CEILINGS AND VSBY AS IT MOVES SW OVER THE ISLANDS. THE BAND IS
EXPECTED TO BE OVER KAUAI BETWEEN 03 AND 06Z...OVER OAHU BETWEEN 07
AND 10Z...OVER MAUI BETWEEN 10Z AND 14Z AND OVER THE BIG ISLAND
BETWEEN 12 AND 15Z. AIRMETS FOR MTN OBSC WILL LIKELY BE NEEDED FOR
ALL ISLANDS AS THE FRONTAL BAND MOVES BY. THE BAND WILL PROBABLY
WEAKEN AS IT MOVES FROM KAUAI TO THE BIG ISLAND.

THE FRONT IS ASSOCIATED WITH A SHARP TROUGH ALOFT WHICH WILL ALSO BE
MOVING SOUTHEAST OVER THE MAIN HAWAIIAN ISLANDS. THIS TROUGH WILL
DROP THE FREEZING LEVEL TO AROUND 11000 FT AND ICING WILL BE
POSSIBLE IN LAYERED CLOUDS ALONG THE FRONT. THE TROUGH MAY ALSO
PRODUCE TURBULENCE ALOFT.

CLOUDS AND SHOWERS WILL DIMINISH RAPIDLY AND WINDS WILL SWING OUT OF
THE NORTH BEHIND THE FRONT. AS THE WINDS SHIFT...SO WILL THE AREAS
OF TURBULENCE.

&&

.MARINE...
MOST OF THE HIGH RESOLUTION GUIDANCE IS POINTING TOWARD LOCALIZED
GALES NEAR THE FRONT AS IT GOES THROUGH...PARTICULARY IN AREAS
THAT ARE PRONE TO ACCELERATION IN THE VARIOUS WIND DIRECTIONS.
ADJUSTMENTS TO THE WIND GRIDS WERE MADE TO INCLUDE GALES WHERE
THEY MIGHT BE EXPECTED. THE REST OF THE FORECAST PHILOSOPHY
REMAINS THE SAME.

SHORT TO MODERATE PERIOD NORTH AND NORTHWEST SWELLS WILL CONTINUE
TO DOMINATE THE SURF THROUGH THE WEEKEND. A SHORT PERIOD NORTH
NORTHWEST SWELL IS FORECAST TO BUILD TONIGHT AND CONTINUE
SATURDAY THROUGH SUNDAY...AS A SURFACE LOW MOVES NEAR OR JUST
NORTH OF KAUAI THEN LIFTS NORTHEAST OF THE STATE. RESULTING SURF
ON NORTH FACING SHORES SHOULD REMAIN BELOW ADVISORY LEVELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 AM HST SATURDAY FOR NIIHAU-KAUAI-OAHU.

WIND ADVISORY UNTIL 6 AM HST SATURDAY FOR BIG ISLAND INTERIOR.

WIND ADVISORY FROM 6 PM THIS EVENING TO 6 AM HST SATURDAY FOR
MOLOKAI-LANAI-KAHOOLAWE-MAUI-KONA-SOUTH BIG ISLAND-BIG ISLAND
NORTH AND EAST-KOHALA.

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

BLIZZARD WARNING FROM 6 PM THIS EVENING TO 6 PM HST SATURDAY FOR
BIG ISLAND SUMMITS.

GALE WARNING UNTIL NOON HST SATURDAY FOR OAHU LEEWARD WATERS-
KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD
WATERS-MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND
WINDWARD WATERS-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST
WATERS.

GALE WARNING UNTIL 6 AM HST SATURDAY FOR KAUAI NORTHWEST WATERS-
KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-OAHU
WINDWARD WATERS.

&&

DISCUSSION/MARINE...R BALLARD
AVIATION...DONALDSON