High Surf in Hawaii, June 21 to 23, 2011

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE HONOLULU HI
454 PM HST TUE JUN 21 2011

.SYNOPSIS...
SURFACE HIGH PRESSURE FAR NORTH OF THE STATE WILL MAINTAIN MODERATE
TRADE WINDS THROUGH THE WORK WEEK...AND THEN STRENGTHEN A LITTLE BIT
BY THIS WEEKEND. AN UPPER LEVEL LOW WILL STALL ACROSS KAUAI TONIGHT
AND ENHANCE THE TRADE SHOWERS ACROSS THE ISLANDS THROUGH THURSDAY
BEFORE MOVING WESTWARD AWAY FROM THE AREA. SHOWERS WILL FOCUS ACROSS
ALL WINDWARD AND MAUKA SIDES WITH THE OCCASIONAL PASSING LEEWARD
SHOWER ON THE SMALLER ISLANDS. A RETURN TO A MORE TYPICAL TRADE WIND
REGIME IS EXPECTED THIS WEEKEND INTO EARLY NEXT WEEK.

&&

.DISCUSSION...
A 1024 MB SURFACE HIGH CENTERED NEAR 35N156W...ABOUT 1000 MILES DUE
NORTH OF HONOLULU...IS DRIVING MODERATE TRADE WIND FLOW ACROSS THE
STATE LATE THIS AFTERNOON. WINDS ARE EXPECTED TO MAINTAIN THROUGH
THURSDAY BEFORE STRENGTHENING A LITTLE BIT FRIDAY AND THIS WEEKEND.

ALOFT...WATER VAPOR IMAGES SHOW AN ELONGATED UPPER LEVEL TROUGH WITH
A LOW CENTERED NEAR KAUAI. THE PRESENCE OF THE UPPER TROUGH IS
PUSHING COLD AIR ALOFT OVER THE WESTERN SIDE OF THE STATE WHICH IS
DESTABILIZING THE ATMOSPHERE SOMEWHAT. SURPRISINGLY...SOUNDINGS FROM
THIS AFTERNOON SHOWED A LITTLE BIT MORE STABLE ATMOSPHERE AT BOTH
LIHUE AND HILO THAN THIS MORNING...THOUGH INVERSIONS ARE FAIRLY WEAK
AND HIGHER THAN A TYPICAL TRADE WIND REGIME. WHILE SCATTERED SHOWERS
HAVE PASSED ACROSS THE STATE THROUGH THE COURSE OF THE DAY...NO
THUNDERSTORMS FORMED. THE THINKING IS THAT THE SURFACE HIGH IS
PRODUCING ENOUGH MIDLEVEL STABILITY/CAPPING FROM THE TRADE WINDS.
SOUNDING 500 MB TEMPERATURES WERE FAIRLY CLOSE TO MODEL OUTPUT OVER
THE STATE AT AROUND -10 DEGREES CELSIUS...BUT AGAIN WITH ENOUGH OF
THAT CAP IS IN PLACE. WITH THE UPPER LOW EXPECTED TO SLOWLY MOVE
WEST TONIGHT BEFORE STALLING UNTIL THURSDAY...WE WILL PROBABLY NOT
GET THUNDERSTORMS ANYWHERE ACROSS THE STATE THE NEXT COUPLE DAYS AND
HAVE REMOVED THEM FROM THE FORECAST. A CHANCE FOR SEA BREEZE DRIVEN
HEAVY RAINFALL MAY STILL BE A POSSIBILITY OVER LEEWARD BIG ISLAND
TOMORROW AFTERNOON. OTHERWISE JUST LOOKING FOR ENHANCED TRADE WIND
SHOWERS FOCUSED MOSTLY OVER WINDWARD AND MAUKA SECTIONS OF THE
ISLANDS WITH OCCASIONAL PASSING LEEWARD SHOWERS ON THE SMALLER
ISLANDS FROM NOW THROUGH THURSDAY. RAINFALL MAXIMUMS WILL OCCUR
DURING THE NIGHTTIME AND EARLY MORNINGS.

THE UPPER LOW IS EXPECTED TO DRIFT WEST OF THE ISLANDS BY FRIDAY IN
WHICH TIME MUCH OF THE SHOWER ACTIVITY WILL MOVE WITH IT. ZONAL FLOW
ALOFT AND AN INCREASE IN THE TRADE WINDS WILL STABILIZE CONDITIONS
MAKING FOR A MORE TYPICAL SUMMERTIME TRADE WIND...WINDWARD/MAUKA
SHOWER...REGIME BEGINNING FRIDAY THROUGH EARLY NEXT WEEK.

&&

.AVIATION...
ALTHOUGH SOME WAVE CLOUDS HAVE FORMED ON OAHU TODAY...WHICH IS AN
INDICATION OF SOME POSSIBLE TURBULENCE...THE INVERSION IS TOO WEAK
AND TRADE WINDS HAVE BEEN ON THE DECLINE. BECAUSE OF THIS...AND THE
FACT THAT THERE HAS BEEN NO OTHER INDICATIONS OF TURBULENCE AROUND
THE ISLANDS...THERE IS NO AIRMET IN EFFECT FOR MOD TURB.

AN AIRMET FOR MT OBSC MAY BE NECESSARY AT SOME POINT DUE TO
INCREASED SHOWER ACTIVITY BRINGING SOME LOWER CIGS TO THE ISLANDS.
THE INCREASED SHOWERS WILL LIKELY ALSO BRING BRIEF MVFR CONDS...AND
POSSIBLY VERY BRIEF IFR CONDS AT TIMES...TO PHLI...PHNY...AND PHTO
THROUGH THE NIGHT. ALSO...STRAY -SHRA/SHRA MAKING IT OVER TO
LEEWARD AIRPORTS MAY BRING BRIEF MVFR CONDS AS WELL. AN UNSTABLE
ATMOSPHERE MAY RESULT IN ISOL +SHRA OVER THE KONA SIDE OF THE
BIG ISLAND THIS AFTERNOON AND INTO THE EARLY EVENING...WHICH WOULD
BRING LESS THAN IDEAL FLYING CONDS FOR THAT AREA. OTHERWISE...VFR
CONDS WILL PREVAIL FOR THE MAIN HAWAIIAN AIRPORTS.

&&

.MARINE...
THE NEAR OFFSHORE BUOYS AT BARBERS POINT AND LANAI ARE SHOWING
THE NEW LONG-PERIOD SOUTH SWELL ARRIVING IN THE ISLANDS THIS
AFTERNOON. THE SWELL WILL CONTINUE BUILDING TONIGHT...PEAK ON
WEDNESDAY AND THEN GRADUALLY DECLINE UNTIL THE WEEKEND. A HIGH
SURF ADVISORY IS IN EFFECT THROUGH THURSDAY. SEE CFWHFO FOR MORE
INFORMATION.

BREAKING WAVES AT HARBOR ENTRANCES MAY MAKE IT DIFFICULT FOR SMALL
VESSELS ENTERING AND LEAVING SOME SOUTH FACING HARBORS. THE SWELL
MAY ALSO CAUSE MODERATE HARBOR SURGES. A MARINE WEATHER STATEMENT
HAS BEEN ISSUED HIGHLIGHTING POTENTIAL HAZARDS TO BOATERS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST THURSDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU SOUTH SHORE-WAIANAE COAST-MOLOKAI
LEEWARD-LANAI MAKAI-KAHOOLAWE-MAUI LEEWARD WEST-MAUI CENTRAL
VALLEY-WINDWARD HALEAKALA-LEEWARD HALEAKALA-KONA-SOUTH BIG
ISLAND-BIG ISLAND NORTH AND EAST.

&&

DISCUSSION/MARINE...FOSTER
AVIATION...HARRISON