High Surf in Hawaii, January 27 to 29, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST SUN JAN 27 2013

.SYNOPSIS...
A COLD FRONT APPROACHING FROM THE NORTHWEST WILL REACH KAUAI LATER
TODAY...THEN MOVE SOUTHEASTWARD DOWN THE MAIN ISLAND CHAIN THROUGH
TONIGHT AND MONDAY. EXPECT HEAVY SHOWERS AND A SLIGHT CHANCE OF
THUNDERSTORMS ALONG AND AHEAD OF THE FRONT. TRADE WINDS ARE EXPECTED
TO RETURN BEGINNING ON TUESDAY...WITH DRIER CONDITIONS AND MAINLY
WINDWARD AND MAUKA SHOWERS.

&&

.DISCUSSION...
A COLD FRONT LESS THAN 200 MILES NORTHWEST OF KAUAI CONTINUES TO
APPROACH THE MAIN ISLAND CHAIN THIS MORNING. RADAR SHOWS HEAVY
SHOWERS ARE FORMING AHEAD OF THE FRONT WITHIN CONVERGENT LOW LEVEL
SOUTHERLY FLOW AROUND KAUAI. HEAVY SHOWERS ARE ALSO FORMING SOUTH OF
OAHU. UNTIL THE FRONT ARRIVES...THESE SHOWERS WILL MOVE ROUGHLY
SOUTH TO NORTH ACROSS THE AREA. BOUTS OF HEAVY RAINFALL ARE EXPECTED
ACROSS NIIHAU...KAUAI AND OAHU THROUGH MONDAY BOTH WITH THE FRONTAL
BAND AND WITH SHOWERS FORMING WITHIN THE MOIST AND UNSTABLE
PREFRONTAL ENVIRONMENT. HEAVY RAINFALL MAY ALSO OCCUR FARTHER
SOUTHEAST DOWN THE ISLAND CHAIN...BUT THE LIKELIHOOD IS LOWER SINCE
WE EXPECT THE FRONT TO GRADUALLY WEAKEN AS IT MOVES SOUTHEASTWARD.
MODELS SHOW RESIDUAL SHOWERS MAY LINGER ACROSS MAUI COUNTY AND
POSSIBLY THE BIG ISLAND THROUGH TUESDAY.

MOST OF THE ENERGY ASSOCIATED WITH THE SUPPORTING UPPER TROUGH IS
NORTH OF THE MAIN ISLANDS...BUT TEMPERATURES ALOFT ARE COLD ENOUGH
AND INSTABILITY IS HIGH ENOUGH TO SUPPORT A SLIGHT CHANCE OF
THUNDERSTORMS IN THE FORECAST THROUGH MONDAY. IF THUNDERSTORMS
OCCUR...THE MAIN THREAT WILL ACROSS NIIHAU...KAUAI...OAHU AND
SURROUNDING WATERS TODAY...MOVING DOWN TO MAUI AND THE BIG ISLAND
TONIGHT AND MONDAY.

SINCE THE FRONT IS APPROACHING FROM THE NORTHWEST...KAUAI AND NIIHAU
WILL BE AFFECTED FIRST. WE EXPECT HEAVY SHOWERS AND POSSIBLE
THUNDERSTORMS WILL AFFECT THESE ISLANDS THIS MORNING...WITH OAHU
LIKELY JOINING THE CLUB BY THIS AFTERNOON. MAUI COUNTY AND THE BIG
ISLAND ISLAND WILL SEE ENHANCED SHOWERS AND POSSIBLE THUNDERSTORMS
TONIGHT THROUGH MONDAY. MODELS DISAGREE ON THE SPEED OF THE FRONT
ACROSS THE ISLANDS AND WHETHER OR NOT THE FRONT DISSIPATES NEAR MAUI
OR PASSES BEYOND THE BIG ISLAND...SO OUR FORECAST MAY BE ADJUSTED AS
THIS EVENT UNFOLDS. RIGHT NOW WE FAVOR THE GFS SOLUTION GIVEN ITS
SLIGHTLY BETTER INITIALIZATION AND RUN-TO-RUN CONSISTENCY. THE FRONT
WILL WEAKEN AND EVENTUALLY DISSIPATE AS ITS PARENT LOW MOVES WELL
AWAY FROM THE AREA BY LATE MONDAY AND INTO EARLY TUESDAY.
HOWEVER...AS TRADE WINDS RETURN LATER IN THE WEEK...ENOUGH REMNANT
MOISTURE WILL LINGER ACROSS THE MAIN HAWAIIAN ISLANDS TO FUEL
WINDWARD AND MAUKA SHOWERS. SOME SNOW SHOWERS ARE POSSIBLE AT THE
BIG ISLAND SUMMITS WITH COLD TEMPERATURES ALOFT MONDAY LATE
AFTERNOON AND EVENING.

&&

.AVIATION...
MOST TAF SITES ARE PRESENTLY EXPERIENCING VFR CONDITIONS EXCEPT FOR
PHLI WHERE THERE HAS BEEN OCNL MVFR AND IFR CONDITIONS ASSOCIATED
WITH PASSING SHOWERS.

AIRMET TANGO IS IN EFFECT FOR THE ENTIRE AREA FOR TEMPO MODERATE
TURB BETWEEN FL300 AND FL400...AND BLW 090 FOR KAUAI AND OAHU.
AIRMET SIERRA IS IN EFFECT FOR MOUNTAIN OBSC FOR KAUAI THIS MORNING.
THIS MAY NEED TO BE EXTENDED TO OAHU THIS AFTERNOON DUE TO CLOUDS
AND SHRA ASSOCIATED WITH AN APPROACHING FRONT.

&&

.MARINE...
A FRONTAL PASSAGE WILL BRING CHOPPY CONDITIONS ACROSS THE LEEWARD
WATERS AROUND THE SMALLER ISLANDS TODAY THROUGH LATE MONDAY.
HEAVY RAINS AND THUNDERSTORMS ARE POSSIBLE THROUGH MONDAY.

THERE IS ENOUGH ENERGY EXPECTED WITH THE NEXT NORTHWEST SWELL TO
PROMPT ISSUANCE OF HIGH SURF WARNINGS FOR EXPOSED NORTH AND/OR WEST
SHORES OF THE SMALLER ISLANDS...BEGINNING AT 6 PM HST TODAY AND
LASTING THROUGH MONDAY AFTERNOON. HIGH SURF ADVISORIES ARE IN EFFECT
SPECIFICALLY FOR WEST FACING SHORES OF OAHU AND THE BIG ISLAND FOR
THE SAME TIME PERIOD.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR NIIHAU-KAUAI-OAHU.

HIGH SURF WARNING FROM 6 PM HST TODAY THROUGH 6 PM HST MONDAY FOR
NORTH AND WEST FACING SHORES OF NIIHAU AND KAUAI...AND NORTH FACING
SHORES OF OAHU MOLOKAI AND MAUI.

HIGH SURF ADVISORY FROM 6 PM HST TODAY THROUGH 6 PM HST MONDAY FOR
WEST FACING SHORES OF OAHU AND THE BIG ISLAND.

&&

PUBLIC/MARINE...POWELL
AVIATION...BURKE