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Hawaiian Islands Synoptic Discussion and Guidance

751
FXHW60 PHFO 102007
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1005 AM HST WED FEB 10 2016

.SYNOPSIS...
LIGHT WINDS AND DRY AND COOL WEATHER WILL CONTINUE TODAY AS A WEAK
SURFACE RIDGE REMAINS NEAR THE ISLANDS. GENTLE TO MODERATE TRADE
WINDS WILL RETURN DURING THE SECOND HALF OF THE WEEK AS A SURFACE
HIGH PASSES NORTH OF THE ISLANDS. THE RETURNING TRADES WILL DELIVER
LOW CLOUDS AND A FEW BRIEF SHOWERS TO WINDWARD SLOPES AND
COASTS...ESPECIALLY ON FRIDAY AND SATURDAY. A FRONT APPROACHING THE
ISLANDS FROM THE NORTHWEST WILL RESULT IN WINDS WEAKENING AND
TURNING TOWARD THE SOUTHEAST THIS WEEKEND. STRONG TRADE WINDS EARLY
NEXT WEEK ARE EXPECTED TO BRING MOISTURE ASSOCIATED WITH THE
DISSIPATING FRONT TO THE ISLANDS FROM MONDAY NIGHT THROUGH
WEDNESDAY.

&&

.DISCUSSION...
A SURFACE FRONT LOCATED ABOUT 175 MILES NORTH OF KAUAI HAS PUSHED
THE SURFACE RIDGE DOWN OVER THE MAIN HAWAIIAN ISLANDS. THE CLOSE
PROXIMITY OF THIS E-W ORIENTED RIDGE HAS CAUSED WINDS TO BE WEAK
ACROSS THE ISLAND CHAIN. THESE LIGHT SYNOPTIC WINDS ALLOWED LOCAL
NIGHTTIME LAND BREEZES TO FORM...AND WITH THE ATMOSPHERE REMAINING
DRY AND STABLE UNDER NEARLY CLEAR SKIES... TEMPERATURES WERE ABLE TO
DIP INTO THE MID- TO UPPER-50S.

THE FORECAST MODELS CONTINUE TO INDICATE THE SURFACE RIDGE WILL
REMAIN IN THE VICINITY OF THE ISLANDS TODAY. THIS WILL MAINTAIN
LIGHT WINDS AND STABLE ATMOSPHERIC CONDITIONS THROUGH THIS AFTERNOON.
LOCAL AFTERNOON SEA BREEZE CIRCULATIONS MAY ALLOW SOME LOW CLOUDS
TO DEVELOP OVER INTERIOR SECTIONS OF SOME ISLANDS...ESPECIALLY THE
LOWER ELEVATIONS OF THE BIG ISLAND...BUT NO SHOWERS ARE ANTICIPATED.

A SURFACE HIGH MOVING BY NORTH OF THE ISLANDS FROM TONIGHT
THROUGH THURSDAY WILL CAUSE A SLIGHT TIGHTENING OF THE PRESSURE
GRADIENT OVER THE STATE. THIS IS EXPECTED TO ALLOW GENTLE TRADES
TO DEVELOP ACROSS MOST AREAS. NOTE THAT SOME OF THE LOW CLOUDS AND
SHOWERS ASSOCIATED WITH THE FRONT THAT IS NOW N OF THE ISLANDS MAY
BE TRANSPORTED BY THE LOW LEVEL TRADE WIND FLOW INTO THE WINDWARD
AREAS...MAINLY FRIDAY AND SATURDAY.

THE SURFACE HIGH WILL EVENTUALLY MOVE TO THE E AND NE DURING THE END
OF THE WEEK...SO ITS INFLUENCE ON LOCAL WEATHER WILL GRADUALLY
DIMINISH. THE ROUNDED WESTERN END OF A SURFACE RIDGE EXTENDING WSW
FROM THIS HIGH IS FORECAST TO REMAIN TO THE N OF THE AREA. THE CLOSE
PROXIMITY OF THIS FEATURE TO THE WESTERN ISLANDS WILL ALLOW THE LOW
LEVEL FLOW TO SHIFT OUT OF THE SE OVER MOST OF THE SMALLER ISLANDS
BY THIS WEEKEND.

A FRONT APPROACHING THE ISLANDS FROM THE NW SUNDAY WILL ERODE THE
WESTERN END OF THE SURFACE RIDGE. THE ARRIVAL OF THIS FRONT WILL
LIKELY BRING AN INCREASE IN LOW CLOUDS AND SHOWERS IN THE VICINITY
OF KAUAI STARTING LATE SUNDAY/EARLY MONDAY. A NEW SURFACE HIGH
BUILDING BEHIND THIS FRONT WILL MOVE E...AND MAY EVENTUALLY CAUSE
MOISTURE ASSOCIATED WITH THE FRONT TO MOVE DOWN THE ISLAND CHAIN
EARLY NEXT WEEK. THE FRONT WILL BRING AN INCREASE IN CLOUDS AND
SHOWERS TO THE ISLANDS...ALONG WITH STRONG AND GUSTY NE TRADE WINDS.

&&

.AVIATION...
NO AIRMETS ARE IN EFFECT AND NONE ARE EXPECTED THROUGH THE PERIOD.
LIGHT WINDS UNDER A WEAK SURFACE RIDGE WILL ALLOW FOR LOCALIZED SEA
BREEZES TO FORM THIS AFTERNOON PRODUCING SOME INTERIOR CLOUDS BUILD
UP. LIGHT TO MODERATE TRADE WINDS WILL BEGIN TO RETURN TONIGHT.

&&

.MARINE...
AN ANTICIPATED LARGE NNW SWELL IS STILL BUILDING AT BUOYS 51001
AND 51101 THIS MORNING...WITH LATEST SWELL OBSERVATIONS CLOSE
TO WHAT WAS FORECAST. THE CAVEAT IS THAT THESE SWELLS WERE
EXPECTED ABOUT 6 TO 8 HOURS AGO...BOTH BY OUR OFFICIAL FORECASTS...
AND BY MOST MODEL GUIDANCE. AS HAS BEEN THE TREND THIS WINTER...
DETERMINISTIC WAVE WATCH III GUIDANCE HAS BEEN TOO FAST IN BRINGING
THE SWELLS IN TO THE ISLANDS. ALSO WORTH NOTING THAT BUOY 51101
RECORDED A MAX SWELL HEIGHT NEAR 19 FEET AT THE SAME TIME THAT BUOY
51001 REPORTED CLOSER TO 15 FEET. THE 19 FOOT OBSERVATIONS MAY HAVE
BEEN SPURIOUS...BUT BOTH BUOYS ARE NOW REPORTING SIG WAVE HEIGHT
NEAR 17 FEET WITH PERIODS BETWEEN 16 AND 19 SECONDS. LONG STORY
SHORT...DANGEROUSLY LARGE SURF CAN BE EXPECTED ALONG EXPOSED N AND W
SHORES TODAY AND TONIGHT... WITH HIGH SURF PERSISTING INTO THURSDAY.

THE SWELL WILL CONTINUE FOR AN EXTENDED PERIOD OF TIME...WITH
SURF REMAINING ELEVATED OVER MULTIPLE TIDE CYCLES. SEE THE
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU /SRDHFO/
FOR MORE DETAILED INFORMATION. LOCALIZED COASTAL FLOODING IS
POSSIBLE IN THE WARNING AREA DUE TO SIGNIFICANT WAVE SET UP AND
RUN UP ALONG THE BEACHES EXPOSED TO THIS SWELL...ESPECIALLY
DURING EACH HIGH TIDE...THIS EVENING AND AGAIN THURSDAY MORNING.

THE SWELL WILL GRADUALLY SUBSIDE FROM THURSDAY NIGHT THROUGH
EARLY FRIDAY...AND SHOULD DROP BELOW THE HIGH SURF ADVISORY
CRITERIA BY LATE FRIDAY. A WNW SWELL EXPECTED SUNDAY WILL
LIKELY PRODUCE SURF REACHING THE HIGH SURF ADVISORY CRITERIA ALONG
MOST N AND W FACING SHORES OF THE SMALLER ISLANDS THROUGH MONDAY.
THE WESTERLY COMPONENT OF THIS SWELL MAY ALSO PRODUCE ADVISORY
LEVEL SURF ALONG THE W FACING SHORES OF THE BIG ISLAND FROM
LATE SUNDAY INTO MONDAY.

A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT THROUGH THURSDAY
FOR MOST HAWAIIAN WATERS DUE TO THE ELEVATED SEAS ASSOCIATED WITH
THE LARGE NNW SWELL. THE STRENGTHENING TRADES MAY CAUSE
WIND SPEEDS TO INCREASE TO THE SCA CRITERIA IN THE TYPICALLY WINDY
WATERS ADJACENT TO THE BIG ISLAND AND THE ISLANDS OF MAUI COUNTY
THURSDAY NIGHT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF WARNING UNTIL 6 PM HST THURSDAY FOR NORTH AND WEST
FACING SHORES OF NIIHAU...KAUAI...OAHU AND MOLOKAI...AND FOR
NORTH FACING SHORES OF MAUI.

HIGH SURF WARNING FROM NOON TODAY TO 6 PM HST THURSDAY FOR WEST
FACING SHORES OF THE BIG ISLAND.

HIGH SURF ADVISORY FROM NOON TODAY TO 6 PM HST THURSDAY FOR NORTH
FACING SHORES OF THE BIG ISLAND.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THURSDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-KAIWI CHANNEL-MAUI
COUNTY WINDWARD WATERS-ALENUIHAHA CHANNEL-BIG ISLAND WINDWARD
WATERS.

&&

$$

DISCUSSION/MARINE...BIRCHARD
AVIATION...EATON