High Surf in Hawaii, April 8 to 9, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
338 AM HST MON APR 8 2013

.SYNOPSIS...
WINDS WILL BECOME WEAKER DURING THE NEXT COUPLE OF DAYS AS HIGH
PRESSURE NORTHEAST OF THE ISLANDS GRADUALLY MOVES AWAY FROM THE
AREA. SEA BREEZES WILL RETURN EACH AFTERNOON AND BRING A FEW
SHOWERS...ESPECIALLY OVER INTERIOR AND MOUNTAIN LOCATIONS. A FRONT
WILL SLOWLY APPROACH THE ISLAND CHAIN FROM THE NORTHWEST DURING THE
NEXT SEVERAL DAYS...AND COULD BRING SOME PRE-FRONTAL SHOWERS TO
KAUAI BY THE END OF THE WORK WEEK.

&&

.DISCUSSION...
A HIGH PRESSURE SYSTEM FAR NE OF THE MAIN HAWAIIAN ISLANDS WILL
CONTINUE TO GRADUALLY MIGRATE E AS A SFC FRONTAL BOUNDARY APPROACHES
THE REGION FROM THE NW. ALSO...A SFC RIDGE EXTENDS TO JUST NW OF
KAUAI AND IS EXPECTED TO MOVE CLOSER TO THE ISLANDS TODAY. THIS WILL
FURTHER WEAKEN PRESSURE GRADIENTS ACROSS THE AREA DURING THE NEXT
COUPLE OF DAYS AND CREATE FAVORABLE CONDITIONS FOR SEA BREEZES TO
DEVELOP EACH AFTERNOON. SUBSIDENCE ALOFT WILL HELP IN KEEPING
CONDITIONS GENERALLY STABLE ACROSS THE ISLANDS THROUGH AT LEAST
TUESDAY.

THE AFOREMENTIONED SFC COLD FRONT IS SLOWLY PUSHING SE AT AROUND 10
MPH...WITH THE LATEST SFC ANALYSIS LOCATING IT AROUND 570 MILES NW
OF KAUAI. THE LEADING EDGE OF ITS ASSOCIATED CLOUD BAND IS MOVING
CLOSER TO THE W PORTIONS OF THE ISLAND CHAIN.

LATEST MODEL GUIDANCE STILL SHOWS REASONABLE CONSENSUS REGARDING THE
EXPECTED WEATHER SCENARIO FOR THE NEXT SEVERAL DAYS. BOTH GLOBAL
MODELS...GFS AND ECMWF...GRADUALLY ERODE THE W END OF THE SFC RIDGE
AS THE FRONT MOVES CLOSER TO THE AREA...THEN STALLING IT SOME
400-500 MILES NW OF KAUAI BY LATE TUE OR WED. THIS OVERALL SYNOPTIC
SETUP WILL BRING FURTHER WEAKENING OF THE TRADE WIND FLOW ACROSS THE
SMALLER ISLANDS...WHICH WILL GRADUALLY TURN TO THE SE. A MORE
PERSISTENT E FLOW SHOULD CONTINUE OVER THE BIG ISLAND THROUGH THE
MIDDLE OF THE WEEK. A GENERALLY DRY PATTERN SHOULD CONTINUE WITH
MAINLY SCATTERED SHOWERS AFFECTING WINDWARD AND MAUKA AREAS EACH DAY
THROUGH THU AS SEA BREEZES DEVELOP.

MODELS BRING A STRONG LOW PRESSURE SYSTEM INTO THE FAR N CPAC BY
THU...WHICH SEEMS TO RE-ENERGIZE THE LINGERING REMNANTS OF THE
STALLED FRONTAL BOUNDARY. BOTH GFS AND ECMWF SHOW INCREASING
MOISTURE AND POTENTIAL FOR SHOWER ACTIVITY DURING THE WEEKEND AS THE
LOW TRACKS E AND PUSHES THE REINVIGORATED FRONT TOWARD THE W EDGE OF
THE MAIN HAWAIIAN ISLANDS. SINCE THIS SCENARIO IS STILL A WEEK
AWAY...THE LONG TERM FORECAST WILL ONLY BE ADJUSTED TO REFLECT
INCREASING COVERAGE OF RAIN ACROSS KAUAI...AND TO A LESSER EXTENT
OAHU. POPS WILL BE LIMITED TO HIGH-END SCATTERED FOR NOW...AND
WILL CONTINUE TO BE ADJUSTED AS NEW MODEL DATA BECOMES AVAILABLE.

&&

.MARINE...
READINGS OF THE NEW WEST NORTHWEST SWELL AT BUOY 51101 INDICATE THE
SIGNIFICANT WAVE HEIGHTS REMAIN 3 TO 4 FEET ABOVE THE GUIDANCE FROM
THE WAVE WATCH III MODEL. RECENT OBSERVATIONS SHOWED SIGNIFICANT
WAVE HEIGHTS OF UP TO 12 FEET WITH WAVE PERIODS OF 15 TO 16 SECONDS.
THIS SWELL IS FORECAST TO CONTINUE SPREADING ACROSS NORTH AND WEST
FACING SHORES OF MOST OF THE SMALLER ISLANDS...WITH SURF HEIGHTS
REACHING THE HIGH SURF WARNING CRITERIA ALONG NORTH AND WEST FACING
SHORES OF KAUAI COUNTY. DUE TO THE WESTERLY SWELL DIRECTION...EXPECT
SOME BLOCKING OF THE SWELL BY KAUAI AND NIIHAU. AS A RESULT...A
HIGH SURF ADVISORY IS IN EFFECT FOR THE ISLANDS EAST OF KAUAI
COUNTY...INCLUDING THE NORTH AND WEST FACING SHORES OF OAHU AND
MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI. WE HAVE ALSO INCLUDED
PORTIONS OF THE WEST FACING SHORES OF THE BIG ISLAND IN THE HIGH
SURF ADVISORY STARTING EARLY THIS AFTERNOON. THE LARGE SURF IS
EXPECTED TO CONTINUE TO IMPACT THE ISLAND CHAIN THROUGH TONIGHT.

BECAUSE THE WEST NORTHWEST SWELL IS LARGER THAN EXPECTED...WE HAVE
ADDED A SMALL CRAFT ADVISORY /SCA/ FOR SEAS OF 10 FEET OR GREATER
OVER THE COASTAL WATERS SURROUNDING KAUAI AND OAHU...AND FOR THE
WINDWARD MAUI COUNTY WATERS THROUGH THIS AFTERNOON. CURRENTLY...THE
FORECAST DOES NOT HAVE ANY SCA CONDITIONS OVER THE COASTAL WATERS
FROM TUESDAY THROUGH FRIDAY.

ELSEWHERE...SMALL...BUT LONG PERIOD SOUTHWEST SWELLS ARE EXPECTED TO
PRODUCE A SLIGHT BUMP IN SURF HEIGHTS ALONG SOUTH FACING SHORES OF
THE ISLANDS THROUGH MID-WEEK.

&&

.AVIATION...
ISOL MVFR CIGS WILL REMAIN CONFINED TO WINDWARD TERRAIN. WINDWARD
TERMINALS MAY ALSO SEE PASSING MVFR CONDITIONS. VFR WILL PREVAIL
ELSEWHERE ALONG WITH SERLY LOW LVL FLOW. AIRMET TANGO REMAINS
POSTED FOR HIGH LVL CAT DUE TO THE JET STREAM OVER THE FA. THE TURB
WILL SUBSIDE SHORTLY AFT 18Z.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

HIGH SURF ADVISORY UNTIL 6 AM HST TUESDAY FOR NORTH AND WEST FACING
SHORES OF OAHU AND MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI.

HIGH SURF WARNING UNTIL 6 PM HST THIS EVENING FOR NORTH AND WEST
FACING SHORES OF NIIHAU AND KAUAI.

HIGH SURF ADVISORY FROM NOON TODAY TO 6 AM HST TUESDAY FOR WEST
FACING SHORES OF THE BIG ISLAND.

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

&&

SYNOPSIS/DISCUSSION...REYNES
MARINE...HOUSTON
AVIATION...DEJESUS