High Surf in Hawaii, December 1 to 5, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
842 PM HST SUN NOV 30 2014

.SYNOPSIS...
HIGH PRESSURE FAR NORTH OF THE STATE WILL WEAKEN OVER THE NEXT
COUPLE OF DAYS...BUT WILL BE FOLLOWED BY A NEW HIGH LATER IN THE
WEEK THAT WILL MAINTAIN TRADE WINDS ACROSS THE ISLANDS. MOST
RAINFALL WILL BE FOCUSED ACROSS WINDWARD AND MAUKA AREAS...WITH
SOME SHOWERS PASSING LEEWARD AS WELL.

&&

.DISCUSSION...
RADAR AND RAIN GAUGE DATA SHOW SCATTERED MOSTLY LIGHT SHOWERS
FOCUSED OVER WINDWARD AREAS THIS EVENING. AT THE SURFACE...FRESH
TO STRONG TRADES CONTINUE OVER THE STATE...TO THE SOUTH OF HIGH
PRESSURE CENTERED FAR TO THE NORTH NEAR 46N150W. DRY/SUBSIDENT
NORTHWEST FLOW PREVAILS ALOFT...BETWEEN A DEEP TROUGH OVER THE
EASTERN PACIFIC AND A RIDGE OUT TOWARD THE DATELINE. THE 00Z
SOUNDINGS AND MIMIC-TPW SATELLITE IMAGERY SHOW A RATHER DRY
AIRMASS PREVAILING OVER THE REGION... WITH THE SOUNDINGS MEASURING
PWATS AROUND ONE INCH OR NEAR THE 25TH PERCENTILE FOR THIS TIME OF
YEAR. WELL DEVELOPED INVERSIONS ARE PRESENT AT TYPICAL HEIGHTS
AROUND 7000 FEET.

EXPECT LITTLE CHANGE OVERNIGHT AND MONDAY. A COUPLE OF SPOKES
OF SLIGHTLY HIGHER MOISTURE (ASSOCIATED WITH THE REMNANTS OF
OLD FRONTS) WILL SWEEP SOUTHWARD THROUGH THE STATE DURING THIS
TIME...BUT OVERALL MOISTURE LEVELS WILL REMAIN UNIMPRESSIVE.
A STEADY INVERSION AROUND 7000 FEET WILL MAINTAIN STABLE/CAPPED
CONDITIONS...SO MOST OF THE SHOWERS SHOULD REMAIN RELATIVELY
LIGHT. CONTINUED GUSTY TRADES WILL CARRY SOME OF THE SHOWERS OVER
INTO LEEWARD AREAS...PARTICULARLY THOSE AREAS JUST TO THE LEE OF
THE MOUNTAINS. THE EXISTING FORECAST APPEARS TO BE ON TRACK...AND
NO UPDATES ARE PLANNED THIS EVENING.

HIGH PRESSURE TO OUR NORTH WILL WEAKEN SOMEWHAT MONDAY NIGHT
THROUGH WEDNESDAY...AS A MID LEVEL TROUGH AND SURFACE COLD FRONT
PASS WELL TO OUR NORTH OVER THE NORTH-CENTRAL PACIFIC. TRADE WINDS
WILL DECREASE DURING THIS TIME...BUT EXPECT LITTLE CHANGE TO THE
EXISTING STABLE WEATHER PATTERN...WITH SCATTERED SHOWERS
CONTINUING TO FOCUS MAINLY OVER WINDWARD AND MAUKA AREAS.

THE 00Z GFS IS IN DECENT AGREEMENT WITH THE 12Z ECMWF FOR THE
SECOND HALF OF THE WEEK...WITH A NEW HIGH BUILDING IN TO OUR
NORTH BEHIND THE FRONT. INCREASINGLY ACTIVE ZONAL FLOW OVER
THE NORTH PACIFIC EVENTUALLY SUPPRESSES THIS HIGH SOUTHWARD
DURING THE WEEKEND...EVOLVING INTO AN EAST-WEST RIDGE AXIS
CENTERED A FEW HUNDRED MILES NORTH OF THE STATE. THE GFS
DOES CONTINUE TO DEVELOP A MORE SIGNIFICANT MID LEVEL TROUGH
BETWEEN 170W AND 180 LATE THIS WEEK...DRAWING SOME DEEPER
TROPICAL MOISTURE NORTHWARD NEAR OR INTO THE STATE FRIDAY AND
FRIDAY NIGHT. THE EC SHOWS A WEAKER TROUGH WITH THE TROPICAL
MOISTURE REMAINING SUPPRESSED TO OUR SOUTH. WE CONTINUE TO FAVOR
THE MORE CONSISTENT EC SOLUTION FOR NOW...WITH A STABLE MODERATE
TRADE WIND PATTERN PREVAILING. BOTH MODELS AGREE IN DEPICTING A
SIGNIFICANT INCREASE IN HIGH LEVEL CLOUDINESS DURING THE MIDDLE
AND LATER PART OF THIS WEEK...DUE TO AN UPPER LEVEL TROUGH
DEVELOPING BETWEEN HAWAII AND THE DATELINE. THEREFORE THE FORECAST
WILL REMAIN CLOUDIER THAN NORMAL...PARTICULARLY ACROSS LEEWARD
AREAS...DURING THOSE TIME PERIODS.

&&

.AVIATION...
VFR WILL PREVAIL IN MOST AREAS TONIGHT AND MONDAY...THOUGH WINDWARD
AND MAUKA AREAS MAY SEE TEMPO MVFR IN LOWER CEILINGS AND SHOWERS
EMBEDDED IN THE TRADE FLOW.

WITH THE BREEZY TRADES...AIRMET TANGO FOR LOW LEVEL TURBULENCE
DOWNWIND FROM HIGHER ELEVATIONS REMAINS POSTED.

&&

.MARINE...
AFTERNOON SURF OBSERVATIONS AND EVENING BUOY DATA CONTINUE TO
SUPPORT THE HIGH SURF ADVISORY FOR EAST FACING SHORES. WITH
WAVEWATCH GUIDANCE THE EXISTING NORTH-NORTHEAST SWELL AND TRADE-
DRIVEN WIND WAVES PERSISTING INTO MONDAY...THE ADVISORY WILL
REMAIN POSTED THROUGH 6 PM MONDAY.

A NEW NORTHWEST SWELL IS EXPECTED TO ARRIVE INTO THE WESTERN
COASTAL WATERS LATE TONIGHT...THEN BUILD THROUGH THE DAY ON
MONDAY AND INTO MONDAY NIGHT. THE FORECASTED 290-300 DEGREE SWELL
DIRECTION WILL RESULT IN SIGNIFICANT SHADOWING BY KAUAI FOR OAHU
AND MAUI COUNTY...BUT THE EXPECTED 17 SECOND PERIOD WILL ALLOW FOR
SOME REFRACTION AROUND KAUAI. WILL AWAIT FURTHER DATA FROM BUOY
51101...WHERE THIS SWELL IS FORECAST TO ARRIVE LATE TONIGHT. FOR
THE EARLY MONDAY MORNING FORECAST PACKAGE WILL NEED TO CONSIDER A
HIGH SURF ADVISORY FOR AT LEAST THE NORTH AND WEST FACING SHORES
OF KAUAI...AND POSSIBLY THE NORTH SHORES OF OAHU...MOLOKAI AND
MAUI AS WELL.

OTHERWISE...THE SUNDAY MORNING ASCAT PASS FOUND AREAS OF 25 KNOT
WINDS SOUTH AND SOUTHWEST OF KAUAI...WHICH COMBINED WITH RECENT
LAND-BASED OBS SUPPORTS THE CONTINUATION OF STRONG TRADE WINDS
ACROSS MANY COASTAL MARINE ZONES. THE STRONG WINDS AND RESULTING
WIND WAVES COMBINED WITH THE ONGOING NNE SWELL AND ARRIVING NW
SWELL WILL REQUIRE THE EXISTING SMALL CRAFT ADVISORY /SCA/ TO
REMAIN POSTED FOR ALL HAWAIIAN COASTAL WATERS THROUGH 6 PM MONDAY.
THERE IS A STRONG LIKELIHOOD THAT THE SCA WILL NEED TO BE EXTENDED
FOR MANY AREAS THROUGH AT LEAST MONDAY NIGHT OR TUESDAY. WILL MAKE
THIS DECISION FOR THE EARLY MONDAY MORNING FORECAST PACKAGE.

&&

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

SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR ALL HAWAIIAN
WATERS.

&&

DISCUSSION/MARINE...JACOBSON
AVIATION...KINEL