High Surf in Hawaii, February 23 to 25, 2009

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON FEB 23 2009

.SYNOPSIS...
HIGH PRESSURE LOCATED FAR NORTH OF THE HAWAIIAN ISLAND CHAIN WILL
MAINTAIN MODERATE TRADE WINDS THROUGH TUESDAY. ANOTHER HIGH WILL
BUILD FAR NORTH NORTHWEST OF THE STATE BY MID-WEEK...BRINGING
STRONGER NORTHEASTERLY WINDS TO THE ISLANDS. RAINFALL WILL REMAIN
RATHER LIGHT AGAIN TODAY...AND WILL BE LIMITED MAINLY TO WINDWARD
AND MAUKA SECTIONS OF THE ALOHA STATE.

&&

.DISCUSSION...
MODERATE TRADE WINDS CONTINUE SOUTH OF A WEAK EAST TO WEST ORIENTED
SURFACE RIDGE LOCATED ABOUT 300 MILES NORTH OF HONOLULU. A SECOND
STRONGER SURFACE HIGH WITH A PRESSURE OF 1036 MB IS LOCATED NEAR THE
DATELINE AT LATITUDE 39N. LOOPS OF WATER VAPOR IMAGERY AND SATELLITE
DERIVED UPPER LEVEL WIND DATA SHOW A LARGE UPPER TROPOSPHERIC LOW
OFF OF THE WEST COAST OF THE U.S. MAINLAND NEAR 43N 135W...OR ALMOST
2000 MILES NORTHEAST OF HILO. AN UPPER LEVEL RIDGE EXTENDS ACROSS
THE CENTRAL PACIFIC NEAR LONGITUDE 166W. THE AXIS OF AN UPPER LEVEL
SHORTWAVE TROUGH...WHICH IS PROPAGATING SOUTHEASTWARD...IS LOCATED
ABOUT 700 MILES NORTH OF HONOLULU...ALONG THE EASTERN FLANK OF THE
RIDGE ALOFT.

ATMOSPHERIC CONDITIONS ACROSS THE HAWAIIAN ISLANDS REMAIN DRY AND
STABLE. AS A RESULT...SATELLITE IMAGERY AND RADAR REFLECTIVITY DATA
INDICATE THERE ARE ONLY A FEW SHOWERS EMBEDDED WITHIN THE SCATTERED
TO BROKEN STRATOCUMULUS CLOUDS THAT ARE OCCURRING MAINLY OVER
WINDWARD AND MAUKA AREAS OF THE ISLANDS. WITH THE STRONG CAPPING
INVERSION NEAR 5500 FEET AND THE DRY LOW-LEVEL AIRMASS UPSTREAM OF
THE STATE...EXPECT RAINFALL TO REMAIN RATHER SPARSE THROUGH TODAY.
THE FEW SHOWERS AND LOW CLOUDS THAT DO OCCUR WILL MAINLY AFFECT
WINDWARD AND MAUKA SECTIONS OF THE ISLANDS.

THE SHORT WAVE TROUGH LOCATED NORTH OF THE STATE WILL CONTINUE TO
PROPAGATE SOUTHEASTWARD BEFORE IT BECOMES ABSORBED WITHIN THE LARGE
UPPER LOW OVER THE EASTERN PACIFIC. THE LATEST MODEL GUIDANCE
INDICATES THERE WILL BE INCREASED TROUGHING/CYCLONIC UPPER LEVEL
FLOW DEVELOPING ACROSS THE STATE. THIS WILL HELP TO WEAKEN AND RAISE
THE SUBSIDENCE INVERSION. MID-TROPOSPHERIC WINDS WILL ALSO SHIFT TO
A MORE SOUTHWESTERLY DIRECTION...WHICH WILL BRING INCREASING
MOISTURE ACROSS THE STATE. AS A RESULT...EXPECT POPS TO BEGIN
INCREASING TO MORE NORMAL CONDITIONS FOR THE PERIOD FROM TONIGHT
THROUGH WEDNESDAY.

DURING THE FIRST HALF OF THE WORK WEEK...THE STRONG SURFACE HIGH
THAT IS CURRENTLY NEAR THE DATELINE WILL SHIFT TO POSITION FAR NORTH
NORTHWEST OF THE STATE. A SECOND UPPER LEVEL SHORTWAVE TROUGH WILL
DEVELOP BEHIND THE ONE MENTIONED ABOVE...AND TAKE A SIMILAR TRACK
PASSING BY FAR NORTHEAST OF THE STATE. A SURFACE TROUGH ASSOCIATED
WITH THE SECOND SHORTWAVE WILL INITIALLY REDUCE THE PRESSURE
GRADIENT SOUTH OF THE BUILDING HIGH PRESSURE TO OUR NORTH NORTHWEST.
THIS WILL KEEP WIND SPEEDS AT MODERATE LEVELS ACROSS THE STATE. ONCE
THAT SHORT WAVE AND THE SURFACE FEATURE MOVE AWAY...THE INFLUENCE OF
THE STRONG HIGH WILL CAUSE THE WINDS TO SHIFT TO A MORE
NORTHEASTERLY DIRECTION AND INCREASE SIGNIFICANTLY ON WEDNESDAY.
THESE NORTHEASTERLY WINDS WILL REMAIN STRONG THROUGH FRIDAY. BY NEXT
WEEKEND...WINDS WILL SHIFT TO A MORE TYPICAL TRADE WIND DIRECTION
FROM THE EAST NORTHEAST. HOWEVER...THE GFS AND ECMWF MODELS INDICATE
THESE WINDS WILL REMAIN RATHER STRONG THROUGH SUNDAY...AND POSSIBLY
INTO NEXT WEEK. THE MODELS ALSO INDICATE RAINFALL WILL BE SLIGHTLY
BELOW NORMAL ACROSS THE STATE FROM THURSDAY INTO NEXT WEEKEND...WITH
ANY SHOWERS THAT DO OCCUR MAINLY CONFINED TO WINDWARD AND MAUKA
SECTIONS OF THE ISLANDS.

&&

.MARINE...
THE CURRENT NORTH NORTHEAST SWELL GENERATED BY THE LARGE LOW FAR
NORTHEAST OF THE STATE WILL CONTINUE TO PRODUCE SURF NEAR THE HIGH
SURF ADVISORY THRESHOLD OF 8 FEET ALONG EAST FACING SHORES OF ALL
ISLANDS. OBSERVATIONS FROM THE MOKAPU BUOY HAVE BEEN RELATIVELY
STEADY WITH A SIGNIFICANT WAVE HEIGHT OF 8 FEET AND A DOMINANT WAVE
PERIOD OF 12 TO 13 SECONDS. THE LATEST WAVEWATCH III MODEL GUIDANCE
CONTINUES TO INDICATE THIS SWELL WILL REMAIN NEAR CURRENT LEVELS
THROUGH TODAY. THIS MODEL DOES SHOW THIS SWELL BEGINNING TO DIMINISH
BY TONIGHT. YET ANOTHER REINFORCING NORTH NORTHEAST SWELL IS
EXPECTED TO ARRIVE WEDNESDAY. NOTE THAT THESE SWELLS FROM THE NORTH
NORTHEAST ALSO RAISE THE POTENTIAL FOR MODERATE SURGES IN HARBORS
WITH ENTRANCES EXPOSED TO THE NORTH AND NORTHEAST...ESPECIALLY HILO
AND KAHULUI HARBORS.

A NEW WEST NORTHWEST SWELL ARRIVED AT BUOY 1 LOCATED NORTHWEST OF
KAUAI LATE SUNDAY AFTERNOON. THIS SWELL WILL CONTINUE TO BUILD
ACROSS THE STATE THIS MORNING. SINCE THE SWELL HEIGHTS AND DOMINANT
WAVE PERIOD AT BUOY 1 WERE SLIGHTLY LARGER THAN EXPECTED...HAVE
ISSUED A HIGH SURF ADVISORY FOR NORTH AND WEST FACING SHORES OF
KAUAI AND NIIHAU TODAY. WE WILL HAVE TO MONITOR BUOY OBSERVATIONS
AND SURF REPORTS THIS MORNING TO DETERMINE IF THIS HIGH SURF
ADVISORY MIGHT NEED TO BE EXTENDED TO ADDITIONAL ISLANDS...SUCH AS
NORTH FACING SHORES OF OAHU...MOLOKAI AND MAUI.

ANOTHER REINFORCING NORTHWEST SWELL IS EXPECTED TO ARRIVE LATE
TUESDAY...WHICH MAY BRING SURF HEIGHTS NEAR THE RESPECTIVE HIGH SURF
ADVISORY THRESHOLDS ALONG NORTH AND WEST FACING SHORES OF SOME OF
THE SMALLER ISLANDS BY LATE TUESDAY OR WEDNESDAY. SURF HEIGHTS ALONG
WEST FACING SHORES OF THE BIG ISLAND WILL LIKELY REMAIN BELOW THE
HIGH SURF ADVISORY THRESHOLD DURING THIS SWELL EVENT.

THE CURRENT NORTH NORTHEAST SWELL...THE NEW WEST NORTHWEST SWELL AND
LOCALLY GENERATED WIND WAVES WILL CAUSE THE COMBINED SEAS TO REACH
THE SMALL CRAFT ADVISORY THRESHOLD OF 10 FEET TODAY FOR THE WATERS
SURROUNDING KAUAI AND OAHU...INCLUDING THE KAUAI AND KAIWI CHANNELS.
AS THE NORTHWEST SWELL CONTINUES TO BUILD TONIGHT...THESE LARGE SEAS
WILL SPREAD DOWN THE ISLAND CHAIN. IN ADDITION TO THE LARGE
SEAS...WIND SPEEDS WILL INCREASE TO THE SMALL CRAFT ADVISORY
THRESHOLD OF 25 KNOTS FOR MOST HAWAIIAN WATERS BY WEDNESDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 600 PM HST THIS AFTERNOON FOR EAST FACING
SHORES OF ALL HAWAIIAN ISLANDS.

HIGH SURF ADVISORY UNTIL 600 PM HST THIS AFTERNOON FOR NORTH AND
WEST FACING SHORES OF KAUAI AND NIIHAU.

SMALL CRAFT ADVISORY UNTIL 600 PM HST TUESDAY FOR THE WATERS
SURROUNDING KAUAI...INCLUDING THE KAUAI CHANNEL...AND THE WINDWARD
OAHU WATERS.

SMALL CRAFT ADVISORY FROM NOON HST TODAY UNTIL 600 PM HST TUESDAY
FOR THE LEEWARD OAHU WATERS AND THE KAIWI CHANNEL.

&&

HOUSTON