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Hawaiian Islands Synoptic Discussion and Guidance

933
FXHW60 PHFO 010754 AAA
AFDHFO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
950 PM HST FRI OCT 31 2014

.UPDATE...
ISOLATED THUNDERSTORMS OVER THE WINDWARD BIG ISLAND HAVE PROMPTED AN
UPDATE OF THE FORECAST FOR THAT ISLAND TONIGHT...ESPECIALLY OVER
THE SUMMITS WHERE FROZEN PRECIPITATION IS POSSIBLE SINCE
TEMPERATURES ARE CURRENTLY HOVERING CLOSE TO THE FREEZING POINT.

&&

.SYNOPSIS...
BREEZY TRADE WINDS WILL CONTINUE ACROSS THE MAIN HAWAIIAN ISLANDS
CHAIN TONIGHT BEFORE DROPPING TO MODERATE LEVELS LATER THIS WEEKEND.
EXPECT WET TRADE WIND WEATHER CONDITIONS TO PERSIST INTO EARLY NEXT
WEEK...ESPECIALLY ACROSS THE WINDWARD AND MAUKA AREAS OF THE ALOHA
STATE.

&&

.DISCUSSION...
THE TIGHT PRESSURE GRADIENT SOUTH OF A 1029 MB SURFACE HIGH CENTERED
NEAR 35N 152W...OR MORE THAN 1000 MILES NORTH NORTHEAST OF
HONOLULU...IS MAINTAINING BREEZY TRADE WINDS ACROSS THE MAIN
HAWAIIAN ISLAND CHAIN THIS EVENING. INFRARED SATELLITE IMAGERY AND
RADAR REFLECTIVITY DATA SHOWED THE LOW CLOUDS AND SHOWERS ASSOCIATED
WITH A DISSIPATED FRONT CONTINUE TO AFFECT MOST OF THE ISLANDS EARLY
THIS EVENING. A MID- TO UPPER-LEVEL TROUGH ABOVE THE ISLANDS HAS
CAUSED A SLIGHT DESTABILIZATION OF THE ATMOSPHERE. AS A RESULT...
SOME OF THE SHOWERS ALONG THE WINDWARD BIG ISLAND APPEAR TO BE
LOCALLY HEAVY. HOWEVER...THE STRONG TRADE WINDS ARE PUSHING THESE
SHOWERS THROUGH AT A FAIRLY RAPID PACE...SO WE EXPECT MOST OF THESE
DOWNPOURS TO BE SHORT-LIVED.

THE SURFACE HIGH FAR NORTH NORTHEAST OF THE ISLANDS...WHICH IS
MOVING SOUTHEAST AT ABOUT 20 MPH...WILL MAINTAIN THE STRONG TRADE
WINDS THROUGH TONIGHT. THE FORECAST MODELS INDICATE THE SURFACE HIGH
WILL WEAKEN SLIGHTLY THIS WEEKEND. THEREFORE...WE ARE EXPECTING THE
TRADE WINDS TO DECREASE SLIGHTLY FROM SATURDAY THROUGH SUNDAY. AT
THE SAME TIME THE MIDDLE TO UPPER LEVEL TROUGH IS EXPECTED TO REMAIN
IN THE VICINITY OF THE ISLANDS THROUGH MONDAY BEFORE IT LIFTS OUT TO
THE NORTH TUESDAY. THE PRESENCE OF THIS FEATURE COMBINED WITH
ENHANCED LOW-LEVEL MOISTURE WILL KEEP TRADE WIND SHOWERS OCCURRING
INTO NEXT WEEK. THIS WILL KEEP SHOWERS ACTIVE...ESPECIALLY OVER
WINDWARD AND MAUKA AREAS WITH A FEW MOVING OVER LEEWARD SECTIONS OF
THE SMALLER ISLANDS.

AS THE SURFACE HIGH CONTINUES TO MOVE EAST AND WEAKEN EARLY NEXT
WEEK...ANOTHER WEAK FRONT IS FORECAST BY THE MODELS TO APPROACH THE
REGION FROM THE NORTHWEST. AS THIS OCCURS...IT WILL CAUSE TRADE
WIND SPEEDS TO GRADUALLY DECREASE TO MODERATE LEVELS. THE TRADES
WILL LIKELY INCREASE AGAIN BY MID-WEEK AS A NEW SURFACE HIGH BUILDS
FAR NORTHWEST OF THE STATE.

&&

.AVIATION...
CLOUDS AND SHRA ASSOCIATED WITH A DISSIPATED FRONT WILL CONTINUE TO
MOVE ACROSS THE ISLANDS THROUGH EARLY SATURDAY...BRINGING BRIEF MVFR
CONDITIONS TO MOST TAF SITES...ESPECIALLY WINDWARD AREAS. THERE ARE
ENOUGH LOW CLOUDS TO WARRANT THE CONTINUATION OF AIRMET MT OBSC FOR
WINDWARD KAUAI AND OAHU...AS WELL AS THE BIG ISLAND. IN FACT...THE
BAND OF LOW CLOUDS REACHING THE BIG ISLAND EARLIER THIS EVENING MAY
SPREAD TO MAUI IN THE NEXT FEW HOURS...BRINGING POSSIBLE MT OBSC
CONDITIONS FOR WINDWARD MAUI LATER THIS EVENING INTO EARLY SATURDAY
MORNING.

MODERATE TO LOCALLY STRONG TRADE WINDS WILL PERSIST ACROSS THE
ISLANDS AS A STRONG SURFACE HIGH PRESSURE REMAINS FAR NORTH OF THE
STATE AT LEAST THROUGH EARLY SATURDAY. AIRMET FOR LOW LEVEL TURB
FOR ALL ISLANDS WILL CONTINUE.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ REMAINS POSTED THROUGH TONIGHT FOR MOST
HAWAIIAN WATERS DUE TO THE STRONG TRADE WINDS AND ROUGH...ELEVATED
SEAS. AS THE TRADE WINDS DROP A NOTCH SATURDAY...CONDITIONS OVER
SOME OF THE WATERS ARE FORECAST TO GRADUALLY IMPROVE BY SATURDAY.
HOWEVER...THE TRADE WINDS WILL LIKELY REMAIN STRONG ENOUGH IN THE
VICINITY OF THE TYPICALLY WINDY WATERS ADJACENT TO THE BIG ISLAND
AND THE ISLANDS OF MAUI COUNTY TO MAINTAIN SCA CONDITIONS THROUGH
SATURDAY NIGHT.

A COMBINATION OF NORTH SWELLS AND TRADE WIND-GENERATED WAVES WILL
CONTINUE TO PRODUCE CHOPPY...ELEVATED SURF ALONG MOST NORTH AND EAST
FACING SHORES OF THE ISLAND CHAIN. AS A RESULT...A HIGH SURF
ADVISORY REMAINS IN EFFECT FOR MOST EAST FACING SHORES THROUGH
SATURDAY AFTERNOON. MODERATE CHOPPY SURF WILL LIKELY CONTINUE ALONG
MOST EAST FACING SHORES FROM SUNDAY INTO EARLY NEXT WEEK.

OTHERWISE...SMALL TO MODERATE NORTH NORTHWEST AND NORTH SWELLS ARE
FORECAST TO MAINTAIN MODEST SURF ALONG MOST NORTH FACING SHORES
THROUGH EARLY NEXT WEEK. HOWEVER...A LARGER SHORT-PERIOD NORTH SWELL
IS EXPECTED TO ARRIVE WEDNESDAY...PEAK WEDNESDAY NIGHT...THEN SLOWLY
SUBSIDE THURSDAY AND FRIDAY. FINALLY...SURF ALONG SOUTH FACING
SHORES OF THE ALOHA STATE WILL REMAIN SMALL THROUGH MONDAY...WITH A
SLIGHT BUMP EXPECTED TUESDAY AS A SMALL LONG PERIOD SWELL ARRIVES.

&&

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

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

SMALL CRAFT ADVISORY UNTIL 6 AM HST SATURDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS-KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS.

&&

$$

UPDATE/DISCUSSION/MARINE...HOUSTON
AVIATION...HUI




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