High Surf in Hawaii, January 11 to 13, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST WED JAN 11 2012

.SYNOPSIS...
EXPECT LIGHT TRADES TODAY AS A SURFACE RIDGE OVER THE ISLANDS BEGINS
TO LIFT TO THE NORTHEAST. CLOUDS AND SHOWERS WILL BE FOUND OVER
WINDWARD AND MAUKA AREAS IN THE TRADE WIND FLOW. A CHANGE IN THE
WEATHER WILL ARRIVE IN THE STATE TOMORROW AS A FRONT SKIRTS THE
NORTHERN END OF THE STATE. THE SURFACE LOW COMBINED WITH AN UPPER
LEVEL SYSTEM WILL HELP TO ENHANCE SHOWERS. SHOWERS WILL DECREASE
FRIDAY AND SATURDAY...WITH ANOTHER INCREASE IN SHOWER ACTIVITY
EXPECTED SUNDAY AFTERNOON.

&&

.DISCUSSION...
THE HIGH PRESSURE RIDGE HAS MOVED DOWN OVER THE MAIN HAWAIIAN
ISLANDS...BRINGING SOME LIGHT WINDS TO THE ISLANDS. OVERALL WE HAVE
HAD DRY CONDITIONS OVER THE ISLANDS OVERNIGHT. THAT/S NOT TO SAY WE
HAVEN/T SEEN ANY SHOWERS...BUT THAT THEY HAVE BEEN FEWER SHOWERS
OVERNIGHT THAN NORMAL. BLENDED TPW SHOWS THIS BELOW NORMAL AIR
IMMEDIATELY UPSTREAM OF THE ISLANDS...SO EXPECT THE CURRENT TREND
OF SHOWER ACTIVITY TO CONTINUE AT LEAST FOR THE START OF THE DAY.

THE NEXT WEATHER SYSTEM THAT PLAYS A FACTOR IN OUR WEATHER IS THE
COLD FRONT ABOUT 520 MILES NORTHWEST OF KAUAI. AN UPPER LEVEL LOW
DEVELOPS IN THE UPPER LEVEL TROUGH CURRENTLY TO THE NORTHWEST OF THE
ISLANDS. THIS UPPER LEVEL LOW WILL BE THE DRIVING FORCE BEHIND OUR
WEATHER FOR THE END OF THE WORK WEEK.

AS THE UPPER LOW MOVES NORTH OF THE ISLANDS THURSDAY...THE MODELS
ARE IN GOOD AGREEMENT WITH BOTH THE PLACEMENT AND STRENGTH OF THE
LOW. HOWEVER AS WE HEAD INTO THE AFTERNOON AND EVENING HOURS...THE
ECMWF WANTS TO STRENGTHEN THE UPPER LOW...BRINGING COLDER UPPER
ATMOSPHERIC TEMPERATURES OVER THE MAIN HAWAIIAN ISLANDS. THE
GFS...NOGAPS AND NAM ALL KEEP THE UPPER LOW STEADY...SO AM PRONE TO
DISCOUNT THE ECMWF RAPID DEVELOPMENT. ALL THE MODELS ARE IN
AGREEMENT WITH PRECIPITABLE WATER VALUES RIGHT AROUND AN INCH OVER
THE ISLANDS ON THURSDAY...WHICH IS ABOUT NORMAL. WITH THIS
SCENARIO...FIND IT A LITTLE DIFFICULT TO CONTINUE THE CHANCE FOR
HEAVY RAIN THURSDAY AFTERNOON AND EVENING. SHOWERS WILL BE ON THE
HEAVIER SIDE THAN NORMAL TRADES...BUT AM NOT EXPECTING ANYTHING MORE
THAN THAT. AS SUCH...AM DROPPING THE HEAVY RAINFALL WORDING FROM THE
FORECAST.

THE UPPER LEVEL SYSTEM LINGERS TO THE NORTHEAST OF THE ISLANDS
THROUGH THE WEEKEND...BUT ALL THE MODELS AGREE THAT IT WILL LIFT TO
THE NORTHEAST ENOUGH TO LIMIT ITS IMPACTS ON THE ISLANDS FOR THE
START OF THE WEEKEND. LOOK FOR A DROP OFF IN SHOWER ACTIVITY FRIDAY
AND SATURDAY.

WINDS SHOULD WEAKEN TONIGHT AHEAD OF THE FRONT...AND THEN SHIFT TO A
LIGHT WESTERLY DIRECTION FOR THURSDAY NIGHT AND FRIDAY...AND
BECOMING NORTHERLY BY SATURDAY AHEAD OF THE NEXT SYSTEM.

THIS NEXT SYSTEM WILL BRING AN INCREASE IN SHOWER ACTIVITY ON SUNDAY
AFTERNOON. THE MODELS BRING MORE MOISTURE WITH THIS SYSTEM...BUT IT
DOESN/T HAVE THE UPPER LEVEL SUPPORT NEEDED TO SUPPORT ANY HEAVY
SHOWERS. SO THE START OF THE NEW WORK WEEK WILL BRING AN INCREASE IN
THE NUMBER OF SHOWERS...AND THUS AN INCREASE IN RAINFALL TOTALS IN
MANY AREAS.

&&

.MARINE...
THE PRIMARY ENERGY FROM THE NEW WEST NORTHWEST SWELL DID NOT SHOW UP
IN THE READINGS AT BUOY 51101 UNTIL AROUND 200 AM HST THIS MORNING.
CURRENTLY...THE READINGS FROM THAT OCEANIC PLATFORM INDICATE THE
SWELL HEIGHT IS ABOUT 10 FEET WITH A PERIOD OF 14 SECONDS. A HIGH
SURF ADVISORY HAS BEEN ISSUED STARTING AT 600 AM HST FOR NORTH AND
WEST FACING SHORES OF NIIHAU...KAUAI AND OAHU...AND FOR NORTH FACING
SHORES OF MOLOKAI AND MAUI. ALSO...A HIGH SURF ADVISORY IS IN EFFECT
FOR THE WEST FACING SHORES OF THE BIG ISLAND THAT ARE EXPOSED TO
THIS SWELL STARTING AT 600 PM HST THIS EVENING. THE HIGH SURF
ADVISORY IS CURRENTLY IN EFFECT THROUGH TONIGHT FOR ALL OF THESE
SHORELINES. NOTE THAT THE ADVISORY MAY NEED TO BE EXTENDED INTO
DAYTIME THURSDAY FOR SOME OF THESE BEACHES...PARTICULARLY THE
LEEWARD BIG ISLAND.

EVEN THOUGH WINDS ACROSS THE COASTAL WATERS ARE NOT VERY STRONG
TODAY...THE INCOMING WEST NORTHWEST SWELL COMBINED WITH LOCALLY
GENERATED WIND WAVES WILL BOOST SEAS OVER THE NORTHWESTERN HAWAIIAN
WATERS TO THE SMALL CRAFT ADVISORY /SCA/ CRITERIA OF 10 FEET OR
GREATER LATER TODAY. THEREFORE...A SCA IS IN EFFECT STARTING AT 600
AM HST THIS MORNING FOR THE WATERS SURROUNDING KAUAI AND OAHU...
INCLUDING THE KAUAI CHANNEL. THE SCA FOR THESE WATERS CONTINUES
THROUGH TONIGHT.

&&

.AVIATION...
VFR CONDITIONS ARE EXPECTED TO CONTINUE FOR ALL TERMINALS TODAY AND
TONIGHT. SOME BRIEF MVFR CEILINGS ARE POSSIBLE FOR THE WINDWARD TAF
SITES DUE TO SHOWERS EMBEDDED WITHIN THE TRADE WIND FLOW.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM 6 AM WEDNESDAY TO 6 AM HST THURSDAY FOR NORTH
AND WEST FACING SHORES OF KAUAI NIIHAU AND OAHU AND FOR NORTH
FACING SHORES OF MAUI AND MOLOKAI.

HIGH SURF ADVISORY FROM 6 PM WEDNESDAY TO 6 AM HST THURSDAY FOR KONA.

SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO 6 AM HST THURSDAY FOR
KAUAI NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD
WATERS-KAUAI CHANNEL-OAHU WINDWARD WATERS-OAHU LEEWARD WATERS.
&&

DISCUSSION/AVIATION...MBALLARD
MARINE...HOUSTON