High Surf Advisory 31, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST FRI AUG 5 2011

.SYNOPSIS...
THE FRESH TO LOCALLY STRONG TRADE WINDS CAUSED BY THE STRONG HIGH
PRESSURE FAR NORTH-NORTHEAST WILL PERSIST INTO SATURDAY. AN UPPER
ATMOSPHERIC LOW WILL MOVE NORTH OF THE ISLANDS SUNDAY NIGHT AND
CAUSE THE PRESSURE GRADIENT TO WEAKEN. TRADE WINDS WILL THEREFORE
WEAKEN TO MODERATE TO FRESH STRENGTH. THERE MAY ALSO BE A SLIGHT
INCREASE IN SHOWERS SUNDAY NIGHT AND MONDAY.

&&

.DISCUSSION...
THE SHOWERS THAT MOVED ONTO THE ISLANDS THIS MORNING SHOULD END BY
THIS AFTERNOON EXCEPT FOR A FEW PERSISTING OVER WINDWARD SECTIONS.
GENERALLY DRIER CONDITIONS ARE EXPECTED TONIGHT AND INTO SUNDAY
EXCEPT FOR THE TRADE SHOWERS THAT TYPICALLY AFFECT THE WINDWARD
SECTIONS AND ESPECIALLY AREAS AROUND WINDWARD MOUNTAINS.

THE ATMOSPHERE IS STABLE WITH A STRONG TEMPERATURE INVERSION AROUND
7 THOUSAND FEET. WATER VAPOR CHANNEL ON SATELLITE IMAGERY WHICH IS
AN INDICATION OF MOISTURE IN THE HIGHER ATMOSPHERE APPEARS
RELATIVELY DRY TO THE NORTHEAST OF THE ISLANDS AND SATELLITE DERIVED
BLENDED TOTAL PRECIPITABLE WATER JUST UPWIND IS NEAR OR JUST UNDER
ONE INCH.

WINDS THROUGH THE LOWER HALF OF THE ATMOSPHERE...BELOW 20 THOUSAND
FEET...HAVE INCREASED TO 20 TO 30 MPH...IN PART REINFORCED BY THE
HIGH ALOFT TO THE NORTH-NORTHWEST. WINDS ON THE HIGHER SUMMITS OF
MAUI AND THE BIG ISLAND HAVE NOT INCREASED AS MUCH AS WOULD BE
EXPECTED UNDER THESE CONDITIONS BUT OBSERVATIONS WILL BE MONITORED
FOR THE POSSIBILITY A WIND ADVISORY MIGHT BE NECESSARY. WINDS AT THE
SURFACE ARE 20 TO 25 MPH AT WINDIER LOCATIONS WITH GUSTS FROM 30 TO
40 MPH. WINDS ARE LIKELY TO INCREASE A LITTLE MORE THIS AFTERNOON.
COMPUTER MODELS SUGGEST STRONGEST WINDS WILL OCCUR TODAY BUT WINDS
SATURDAY WILL BE ONLY SLIGHTLY LOWER.

SUNDAY AND MONDAY WILL SEE WINDS BACK DOWN IN THE MODERATE TO NEAR
FRESH RANGE AS THE SURFACE HIGH WEAKENS AND AN UPPER LOW SAGS
SOUTHWARD TOWARD OUR ISLANDS. THIS UPPER LOW WILL REMAIN JUST
NORTH... NOT IN A POSITION THAT WOULD SPELL A SIGNIFICANT CHANGE BUT
AT LEAST WILL ALLOW ENHANCED SHOWER ACTIVITY. COMPUTER MODELS ALSO
DEPICT A WEAK INVERTED SURFACE TROUGH MOVING OVER THE BIG ISLAND
SUNDAY NIGHT IN RESPONSE TO THE UPPER LOW. THIS COULD MEAN AN
INCREASE IN SHOWERS FOR WINDWARD AREAS OF THE BIG ISLAND AND MAUI.
TRADE WINDS WILL BRIEFLY BECOME EAST-NORTHEASTERLY SUNDAY.

&&

.AVIATION...
AIRMET TANGO CONTINUES FOR LOW LEVEL TURBULENCE FOR AREAS OVER AND
IMMEDIATE S THROUGH W OF THE MOUNTAINS ON THE MAIN HAWAIIAN ISLANDS
DUE TO THE STRONG WINDS. MVFR CONDITIONS MAY PERSIST FOR WINDWARD
TAF SITES THIS MORNING BUT IMPROVEMENT EXPECTED THIS AFTERNOON
SHOULD BRING A RETURN OF VFR CONDITIONS.

&&

.MARINE...
ELEVATED SHORT PERIOD SWELL IS EXPECTED FOR THE EAST FACING SHORES
THROUGH THE WEEKEND.  SURF HEIGHTS LIKELY TO REMAIN JUST BELOW
ADVISORY LEVEL ON EAST SHORES BUT CONDITIONS WILL BE MONITORED IN
CASE AN ADVISORY IS NEEDED. SMALL SOUTH SWELLS WILL PERSIST INTO
EARLY NEXT WEEK. SMALL LONG PERIOD WEST SWELL FROM TYPHOON MUIFA MAY
REACH THE ISLANDS OVER THE WEEKEND.

A SMALL CRAFT ADVISORY CONTINUES FOR ALL COASTAL WATERS DUE TO THE
WINDS THROUGH SATURDAY. WINDS ARE EXPECTED TO WEAKEN BEGINNING ON
SUNDAY BUT REMAIN IN THE MODERATE TO NEAR FRESH CATEGORY THROUGH
NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 PM HST SATURDAY FOR ALL COASTAL WATERS.

&&

HOAG