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Hawaiian Islands Synoptic Discussion and Guidance

946
FXHW60 PHFO 030158
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
358 PM HST SUN AUG 2 2015

.SYNOPSIS...
MODERATE TO LOCALIZED FRESH TRADES WINDS ARE EXPECTED TO EASE
SLIGHTLY BY MONDAY. SHOWERS WILL BE MOSTLY CONCENTRATED OVER THE
WINDWARD BIG ISLAND TODAY AND TONIGHT. HURRICANE GUILLERMO WILL
WEAKEN TO A TROPICAL STORM THEN APPROACH THE EASTERN PORTION OF
THE STATE EARLY WEDNESDAY MORNING. GUILLERMO WILL THEN TRACK WEST
NORTHWEST ACROSS THE REST OF THE STATE THROUGH THURSDAY. A MODERATE
TO LOCALLY STRONG TRADE WIND FLOW WILL RESUME FRIDAY INTO THE
WEEKEND.

&&

.DISCUSSION...
MODERATE TO FRESH TRADES BROUGHT ON BY A PASSING DISTURBANCE SOUTH
OF THE ISLANDS WILL CONTINUE THROUGH THIS EVENING BEFORE EASING
OFF TO MODERATE SPEEDS MONDAY AND TUESDAY. UPPER LEVEL RIDGING
OVER THE ISLANDS WILL KEEP CONDITIONS MOSTLY DRY AND STABLE OVER
THE NEXT COUPLE OF DAYS.

THE ONLY EXCEPTION TO THIS IS ON THE WINDWARD SIDE OF THE BIG
ISLAND WHERE A BAND OF CLOUDS AND SHOWERS ORIENTED WITH THE TRADE
WINDS WILL CONTINUE TO FUNNEL IN THROUGH MONDAY. RADAR SHOWED A
FEW HEAVIER SHOWERS AND ISOLATED THUNDERSTORMS IN THE KAU AND
SOUTH KONA DISTRICTS DUE TO THE LEEWARD SEA BREEZE LIFTING THE
MOIST AIR OVER THE MOUNTAINS. THUS...HAVE ADDED A SLIGHT CHANCE OF
THUNDERSTORMS FOR THIS EVENING ACROSS THE BIG ISLAND.

SUBSIDENCE AHEAD OF APPROACHING HURRICANE GUILLERMO MAY
OCCUR ON TUESDAY WHICH MEANS THINNING OUT THE REMNANT MOISTURE
FROM THE BIG ISLAND...AND CONTINUING THE DRY CONDITIONS FOR ALL
OTHER ISLANDS.

HURRICANE GUILLERMO IS FORECAST TO BE WEAKEN TO A TROPICAL STORM
AS IT REACHES NEAR THE BIG ISLAND EARLY WEDNESDAY MORNING...THEN
TRACK TO THE WEST-NORTHWEST ALONG THE SMALLER ISLANDS DURING THE
WEDNESDAY AND THURSDAY. THERE ARE NO WATCHES IN EFFECT FOR THE
MAIN HAWAIIAN ISLANDS FOR GUILLERMO AS OF YET...BUT ASSUMING THE
FORECAST TRACK...INTENSITY...AND MODEL GUIDANCE CONTINUES TO
SUPPORT IMPACT...IT MAY BE FIRST ISSUED ON MONDAY MORNING FOR THE
EASTERN PORTIONS OF THE STATE AS THOSE AREAS WOULD BE FIRST TO BE
IMPACTED. GUILLERMO/S BIGGEST THREAT TO HAWAII WILL BE
RAINFALL...WITH THE POTENTIAL FOR FLASH FLOODING ACROSS ALL
ISLANDS. A HYDROLOGIC OUTLOOK...SEE PRODUCT ESFHFO ON OUR
WEBSITE...HAS BEEN ISSUED TO OUTLINE THE MID-RANGE FORECAST FLOOD
THREAT. GUILLERMO ALSO HAS THE POTENTIAL TO BRING WINDY CONDITIONS
AND THUNDERSTORMS.

AFTER THE PASSAGE OF GUILLERMO...MODELS ARE LOOKING AT A MORE
TYPICAL MODERATE TO LOCALLY STRONG TRADE WIND PATTERN FOR THE
UPCOMING WEEKEND.


&&

.AVIATION...
VFR CONDITIONS PREVAIL AT MOST TAF SITES WITH THE EXCEPTION OF PHTO
WHERE THERE HAS BEEN OCCASIONAL MVFR AND BRIEF IFR CONDITIONS BEING
REPORTED DUE TO LOW CLOUDS AND SHRA. EXPECT THESE CONDITIONS TO
CONTINUE THROUGH MOST OF THE NIGHT. AIRMET SIERRA REMAINS POSTED
ALONG THE WINDWARD SLOPES OF THE BIG ISLAND DUE TO LOW CLOUDS AND
SHRA. THERE MAY ALSO BE SOME LOCAL MVFR CONDITIONS OVER WINDWARD
SLOPES OF THE SMALLER ISLANDS AS WELL. AIRMET TANGO REMAINS POSTED
FOR LOW LEVEL TURBULENCE DUE TO MODERATE TO FRESH TRADE WINDS. WINDS
ARE EXPECTED TO GRADUALLY DIMINISH TONIGHT AND MONDAY.


&&

.MARINE...
THE SMALL CRAFT ADVISORY /SCA/ CONTINUES THROUGH 6 AM HST MONDAY
MORNING. MODELS KEEP SCA STRENGTH TRADE WINDS INTO THE FIRST HALF
OF THE TONIGHT BEFORE EASING OFF. WINDS AND SEAS WILL RAMP UP
AGAIN WITH THE APPROACH OF TROPICAL CYCLONE GUILLERMO.

GUILLERMO IS FORECAST TO REACH OUR OFFSHORE WATERS SOME 270 MILES
EAST SOUTHEAST OF THE BIG ISLAND ON TUESDAY AT TROPICAL STORM
STRENGTH AND CONTINUE SLOWLY WEAKEN AS IT NEARS THE ISLANDS.

GUILLERMO HAS GENERATED A LARGE EAST SWELL AIMED TOWARDS THE
ISLANDS. BUOY 51004...LOCATED AROUND 230 MILES SOUTHEAST OF THE
BIG ISLAND...HAS PICKED UP ON SOME OF THE HIGHER ENERGY FORERUNNER
WAVES HEADED THIS WAY. A HIGH SURF ADVISORY IS NOW IN EFFECT FOR
THE EAST FACING SHORES OF MOST ISLANDS AND CONTINUES THROUGH TUESDAY.
THE SURF WILL SPREAD TO THE WESTERN END OF THE STATE TONIGHT...PEAK
MONDAY NIGHT...FOLLOWED BY A GRADUAL DECLINE TUESDAY. THE EFFECTS
OF GUILLERMO WILL LIKELY BOOST LOCALLY GENERATED WIND WAVES AND
SURGE TUESDAY NIGHT / WEDNESDAY THROUGH THURSDAY. MORE SPECIFIC
DETAILS OF MARINE HAZARDS ASSOCIATED WITH GUILLERMO WOULD BE
DETERMINED IN THE NEXT DAY IF / WHEN WE DECIDE TO ISSUE WATCHES
AND SUBSEQUENT WARNINGS. ADVERSE EFFECTS FOR ANY OF THE HAWAIIAN
COASTAL AND OFFSHORE WATERS CANNOT NOT BE RULED OUT.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST TUESDAY FOR EAST FACING SHORES
OF KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

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


&&

$$

DISCUSSION/MARINE...FOSTER
AVIATION...BURKE



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