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Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office

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Hawaiian Islands Synoptic Discussion and Guidance

112
FXHW60 PHFO 101419
AFDHFO

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

.SYNOPSIS...
LIGHT WINDS AND DRY WEATHER WILL CONTINUE TODAY DUE TO A WEAK
SURFACE RIDGE IN THE VICINITY OF THE ISLANDS. GENTLE TRADE WINDS
WILL RETURN DURING THE SECOND HALF OF THIS WEEK AS A SURFACE HIGH
PASSES NORTH OF THE ALOHA STATE. THE TRADES WILL CARRY SOME LOW
CLOUDS AND SHOWERS MAINLY TO WINDWARD FACING SLOPES. A FRONT
APPROACHING THE ISLANDS FROM THE NORTHWEST WILL RESULT IN WINDS
TURNING MORE SOUTHEASTERLY OVER THE SMALLER ISLANDS THIS WEEKEND.

&&

.DISCUSSION...
A SURFACE FRONT LOCATED ABOUT 175 MILES NORTH OF LIHUE HAS PUSHED
THE SURFACE RIDGE DOWN OVER THE MAIN HAWAIIAN ISLANDS. THE CLOSE
PROXIMITY OF THIS EAST TO WEST ORIENTED RIDGE TO THE STATE HAS
CAUSED THE BACKGROUND WINDS TO BE WEAK ACROSS THE ISLAND CHAIN.
THESE LIGHT SYNOPTIC WINDS ALLOWED LOCAL NIGHTTIME LAND BREEZES
TO FORM OVER THE INTERIOR SECTIONS OF MOST ISLANDS TONIGHT. IN
ADDITION TO THE LIGHT WINDS...THE ATMOSPHERE REMAINS RATHER DRY
AND STABLE. THERE ARE FEW...IF ANY...LOW CLOUDS AND SHOWERS OVER
THE ISLANDS. THE DOWNSLOPE WINDS AND THE RADIATIONAL COOLING DUE
TO THE CLEAR SKIES OVER THE ISLANDS HAS ALSO RESULTED IN COOL
TEMPERATURES ACROSS THE STATE.

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 FEW 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 NORTH OF THE
ISLANDS MAY BE TRANSPORTED BY THE LOW LEVEL TRADE WIND FLOW INTO
THE WINDWARD SIDES OF SOME OF THE ISLANDS FROM TONIGHT INTO
THURSDAY.

THE SURFACE HIGH WILL EVENTUALLY MOVE TO THE EAST AND THEN TO THE
NORTHEAST DURING THE END OF THE WEEK...SO ITS INFLUENCE ON LOCAL
WEATHER WILL GRADUALLY DIMINISH. THE ROUNDED WESTERN END OF A
SURFACE RIDGE EXTENDING WEST-SOUTHWEST FROM THIS HIGH IS FORECAST
TO REMAIN TO THE NORTH OF THE AREA. THE CLOSE PROXIMITY OF THIS
FEATURE TO THE WESTERN ISLANDS WILL ALLOW THE LOW LEVEL FLOW TO
SHIFT OUT OF THE EAST-SOUTHEAST TO SOUTHEAST OVER MOST OF THE
SMALLER ISLANDS BY THIS WEEKEND.

A FRONT APPROACHING THE ISLANDS FROM THE NORTHWEST 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. A NEW SURFACE HIGH
BUILDING BEHIND THIS FRONT WILL MOVE EASTWARD...AND MAY EVENTUALLY
CAUSE 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 NORTH TO NORTHEAST WINDS. THE LATEST
MODEL OUTPUT DOES NOT APPEAR TO SHOW HEAVY RAINFALL ASSOCIATED
WITH THE FRONTAL PASSAGE.

&&

.AVIATION...
VFR COND WILL PREVAIL. NO AIRMETS ARE IN EFFECT AND NONE ARE
ANTICIPATED THROUGH TONIGHT.

&&

.MARINE...
THE LONG PERIOD ENERGY FROM THE LATEST VERY LARGE WINTERTIME
NORTH-NORTHWEST SWELL ARRIVED AT BUOY 51001 AND 51101 EARLIER
TONIGHT. HOWEVER...THE SWELL HEIGHT HAS BEEN RUNNING 3 TO 4 FEET
BELOW THE WAVE WATCH III MODEL GUIDANCE. THE HANALEI BUOY ALSO HAS
A DOMINANT WAVE PERIOD OF 18 SECONDS IN THE MOST RECENT READING...
SO THE SWELL HAS JUST ARRIVED IN THE ISLANDS. THIS IS APPROXIMATELY
6 HOURS LATER THAN EXPECTED. THEREFORE...WE STILL EXPECT THE SWELL
TO BUILD SIGNIFICANTLY ACROSS THE STATE LATER TODAY AND TONIGHT.

SURF PRODUCED BY THIS SWELL WILL LIKELY INCREASE TO THE HIGH SURF
WARNING CRITERIA ALONG MOST NORTH AND WEST FACING SHORES OF THE
SMALLER HAWAIIAN ISLANDS LATER THIS MORNING. IN ADDITION...THE
ENERGY FROM THIS SWELL WILL ALSO LIKELY REACH BOTH THE WEST AND
NORTH FACING SHORES OF THE BIG ISLAND LATER TODAY AND TONIGHT. AS
A RESULT...A HIGH SURF WARNING HAS BEEN ISSUED STARTING AT NOON
HST WEDNESDAY FOR WEST FACING SHORES OF THE BIG ISLAND...WHILE A
HIGH SURF ADVISORY WILL BE IN EFFECT STARTING AT NOON HST FOR
NORTH FACING SHORES OF THE BIG ISLAND.

NOTE THAT THIS NORTH-NORTHWEST SWELL WILL CONTINUE FOR AN
EXTENDED PERIOD OF TIME...WHICH MEANS THAT SURF WILL REMAIN
ELEVATED OVER MULTIPLE TIDE CYCLES. SEE THE COLLABORATIVE
NEARSHORE SWELL AND WIND FORECAST FOR OAHU FOR MORE DETAILED
INFORMATION ABOUT THIS SWELL. 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 FROM LATER TODAY INTO THURSDAY.

THIS SWELL WILL GRADUALLY SUBSIDE FROM THURSDAY NIGHT THROUGH
EARLY FRIDAY...AND SHOULD DROP BELOW THE HIGH SURF ADVISORY
CRITERIA BY LATE FRIDAY. ANOTHER WEST-NORTHWEST SWELL IS EXPECTED
TO ARRIVE SUNDAY...AND PRODUCE SURF REACHING THE HIGH SURF
ADVISORY CRITERIA ALONG MOST NORTH AND WEST FACING SHORES OF THE
SMALLER ISLANDS SUNDAY AND MONDAY. THE WESTERLY COMPONENT OF THIS
SWELL MAY ALSO PRODUCE ADVISORY LEVEL SURF ALONG THE WEST 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 NEW NORTH-NORTHWEST 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...HOUSTON
AVIATION...DONALDSON


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