High Surf in Hawaii, August 9 to 12, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST SUN AUG 9 2015

.SYNOPSIS...
LOCALLY BREEZY TRADE WINDS WILL GRADUALLY DECREASE ON MONDAY AND
TUESDAY AS HIGH PRESSURE CENTERED FAR NORTH OF THE ISLANDS SHIFTS
EAST AND WEAKENS. FOR THE NEXT FEW DAYS SHOWERS WILL REMAIN FOCUSED
ALONG WINDWARD SLOPES...THOUGH A BATCH OF MOISTURE MOVING ACROSS THE
SMALLER ISLANDS TODAY WILL CAUSE SOME RAINFALL TO SPREAD OVER TO
LEEWARD AREAS. HEADING INTO THE MIDDLE OF THE WORK WEEK...THE LOCAL
FORECAST HINGES UPON THE EVOLUTION OF HURRICANE HILDA.

&&

.DISCUSSION...
LOCALLY BREEZY TRADE WINDS ARE IN STORE TODAY. AN UPDATE WAS SENT
OUT TO BOOST WIND SPEEDS...SINCE AN OVERNIGHT ASCAT PASS REVEALED
STRONGER WINDS. A 1029 MB HIGH SITTING ABOUT 1200 MILES NORTH OF THE
STATE WILL DRIVE THE GUSTY TRADES TODAY. TRADES WILL GRADUALLY EASE
ON MONDAY AND TUESDAY AS THE HIGH DRIFTS TO THE NORTHEAST AND AN
INTENSIFYING MID LEVEL TROUGH JUST NORTH OF THE ISLANDS ERODES THE
LOCAL SURFACE PRESSURE GRADIENT.

SHOWERS WILL REMAIN FOCUSED ALONG TYPICAL WINDWARD SLOPES FOR THE
NEXT FEW DAYS. A DIFFUSE BATCH OF MOISTURE MOVING ALONG THE TRADE
WIND FLOW WILL KEEP SHOWERS ACTIVE ACROSS THE SMALLER ISLANDS
TODAY...ALLOWING SOME SHOWERS TO BRIEFLY SPILL OVER TO LEEWARD AREAS.
EXPECT THE KONA SLOPES OF THE BIG ISLAND TO CONTINUE TO EXPERIENCE
AFTERNOON CLOUDS AND A FEW SHOWERS.

UNCERTAINTY INCREASES GREATLY IN THE TUESDAY NIGHT AND WEDNESDAY
TIME FRAME. THE OFFICIAL CENTRAL PACIFIC HURRICANE CENTER FORECAST
FOR HURRICANE HILDA SHOWS THE SYSTEM WEAKENING AS IT APPROACHES THE
STATE FROM THE SOUTHEAST. ALTHOUGH HILDA IS A COMPACT TROPICAL
CYCLONE...THE LOW LEVEL MOISTURE FIELD SURROUNDING IT RATHER
BROAD...WHICH MEANS THAT THE ISLANDS COULD SEE AN INCREASE IN SHOWER
ACTIVITY EVEN WHEN HILDA IS SEVERAL HUNDRED MILES AWAY. TRADE WINDS
WILL LIKELY HOLD INTO WEDNESDAY WITH A GOOD CHANCE FOR A GRADUAL
INCREASE IN SHOWER ACTIVITY FROM THE EAST.

LATE WEDNESDAY AND BEYOND...FORECAST UNCERTAINTY ASSOCIATED WITH
HILDA IS HIGH. ALL INTERESTS IN THE STATE OF HAWAII SHOULD KEEP
MONITORING THE PROGRESS OF HILDA BY LISTENING TO THE NOAA WEATHER
RADIO...LOCAL MEDIA OUTLETS OR VISITING OUR WEBSITE AT
WWW.WEATHER.GOV/HAWAII FOR THE LATEST BULLETINS AND WEATHER
PRODUCTS.

&&

.AVIATION...
APPROACH OF HURRICANE HILDA NOT YET AFFECTING THE STURDY TRADE WINDS
PREVAILING ACROSS THE HAWAIIAN ISLANDS. SHE IS TOO FAR AWAY ATTM.
THE TYPICAL TRADE WIND REGIME OF PASSING SHOWERS AND GUSTY
EAST-NORTHEAST WINDS TO CONTINUE INTO MONDAY. THUS EXPECT OCCASIONAL
MVFR CONDITIONS DUE TO CLOUDS AND SHOWERS MAINLY ALONG THE WINDWARD
SECTIONS...SPILLING OVER ONTO THE LEE SIDES AT TIMES. 12Z SOUNDING
IMPLYING CLOUD TOPS BETWEEN 8000 AND 10000 FEET IN MOST AREAS.

AIRMET FOR LOW LEVEL TURBULENCE JUST DOWNWIND OF THE MOUNTAINS
CONTINUES UNTIL FURTHER NOTICE DUE TO THE FREQUENTLY STRONG TRADES.

&&

.MARINE...
THE SMALL CRAFT ADVISORY /SCA/ WAS EXPANDED FROM THE TYPICALLY WINDY
WATERS AROUND THE BIG ISLAND AND MAUI TO COVER ADDITION WATERS AND
CHANNELS AROUND OAHU AND KAUAI. AN OVERNIGHT ASCAT PASS SHOWED
STRONGER WINDS...PROMPTING AN EXPANSION OF THE SCA THROUGH THE DAY
TODAY. WITH A DECLINE IN THE WINDS EXPECTED TO BEGIN TONIGHT...THE
SCA IS SCALED BACK TO THE TYPICALLY WINDY WATERS AROUND THE BIG
ISLAND AND MAUI TONIGHT. ON MONDAY...TRADES WILL CONTINUE TO WEAKEN
AND WILL BEGIN TO BACK OUT OF THE NORTHEAST. WE MAY HAVE TO KEEP
PORTIONS OF THE SCA GOING AT THAT TIME...MAINLY WATERS AROUND MAUI
AND THE ALENUIHAHA CHANNEL.

HEADING INTO MIDWEEK...UNCERTAINTY REGARDING THE TRACK AND INTENSITY
OF HILDA INCREASES SUBSTANTIALLY. ALL INTERESTS IN THE STATE OF
HAWAII SHOULD KEEP MONITORING THE PROGRESS OF HILDA BY LISTENING TO
THE NOAA WEATHER RADIO...LOCAL MEDIA OUTLETS OR VISITING OUR WEBSITE
AT WWW.WEATHER.GOV/HAWAII.

EAST-SOUTHEAST SWELL FROM HILDA WILL GRADUALLY BUILD OVER THE NEXT
DAY OR TWO. A HIGH SURF ADVISORY GOES INTO EFFECT THIS EVENING FOR
EAST FACING SHORES OF THE BIG ISLAND AND EAST MAUI. THE ADVISORY
RUNS THROUGH TUESDAY NIGHT BUT WILL LIKELY NEED TO BE EXTENDED...
DEPENDING ON THE FUTURE TRACK AND INTENSITY OF HILDA. ALTHOUGH THE
OTHER ISLANDS SHOULD REMAIN MOSTLY BLOCKED FROM THE HILDA SWELL
DURING THE NEXT SEVERAL DAYS...SOME REFRACTED SWELL ENERGY WILL
OCCUR.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM THIS EVENING THROUGH 6 AM HST WEDNESDAY FOR
EAST FACING SHORES OF THE BIG ISLAND AND MAUI.

SMALL CRAFT ADVISORY UNTIL 6 AM HST MONDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

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

&&

DISCUSSION/MARINE...WROE
AVIATION...FUJII