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Hawaiian Islands Synoptic Discussion and Guidance

755
FXHW60 PHFO 100635
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN MAR 9 2014

.SYNOPSIS...
TRADE WIND WEATHER WILL CONTINUE ACROSS THE MAIN HAWAIIAN ISLANDS
THROUGH MOST OF THE FORECAST PERIOD AS HIGH PRESSURE BECOMES
DOMINANT TO OUR NORTH. CLOUDS AND SHOWERS WILL FAVOR WINDWARD AND
MAUKA AREAS...EXCEPT FOR AFTERNOON BUILDUPS ALONG LEEWARD SLOPES OF
THE BIG ISLAND EACH AFTERNOON. A COLD FRONT WILL REACH THE ISLANDS
FRIDAY...USHERING IN STRONG AND GUSTY TRADE WINDS IN ITS WAKE FOR
THE WEEKEND.

&&

.DISCUSSION...
A 1028 MB HIGH NEAR 35N140W...FAR NORTHEAST OF THE MAIN HAWAIIAN
ISLANDS...HAS AN ASSOCIATED RIDGE EXTENDING SOUTHWEST THROUGH
27N155W AND 23N172W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND
EQUATORIAL LOW PRESSURE IS SUFFICIENTLY STEEP TO SUPPORT MODERATE
EASTERLY TRADE WINDS ACROSS LOCAL WATERS THIS EVENING. THE OLD
FRONTAL BOUNDARY EAST OF THE BIG ISLAND HAS WASHED OUT AND
ASSOCIATED LAYERED CLOUDS ARE LONG GONE...LEAVING US WITH AN
ABUNDANCE OF BROKEN LOW CLOUDS EMBEDDED WITHIN THE TRADES. SATELLITE
LOOP SHOWS THESE LOW CLOUDS FAVORING WINDWARD AND MAUKA AREAS...WITH
RADAR SHOWING MODERATE SHOWERS ACROSS THE KOOLAU RANGE ON
OAHU...WINDWARD HALEAKALA SLOPES ON MAUI...WINDWARD AND SOUTHEAST
SLOPES ON THE BIG ISLAND AND ACROSS THE EASTERN HALF OF KAUAI. WE
EXPECT A CONTINUED PATTERN OF LOW CLOUDS AND SHOWERS FAVORING
WINDWARD AND MAUKA AREAS THROUGH THE WEEK. TROUGHING JUST WEST OF
160W HAS REINTRODUCED BROKEN MIDDLE CLOUDS TO KAUAI NORTHWEST
WATERS THIS EVENING AND SATELLITE LOOP SHOWS THESE MAY SPREAD ACROSS
KAUAI OVERNIGHT.

MODELS SHOW THE HIGH TO OUR NORTHEAST WILL MOVE AWAY OVER THE NEXT
48 HOURS WHILE ANOTHER HIGH NOSES IN FROM THE WEST. IN THE SHORT
INTERVAL...THE RIDGE WILL BE WEAKER TO OUR NORTH AND TRADE WINDS
ACROSS LOCAL WATERS WILL DECREASE DURING THE DAY MONDAY. BY
TUESDAY...THE SECOND HIGH SHOULD BE IN PLACE TO OUR NORTH AND TRADE
WINDS SHOULD BE STRONGER IN RESPONSE. WIND DIRECTION WILL BE
NORTHEASTERLY INSTEAD OF EASTERLY AND TRADE FLOW SHOULD CONTINUE
UNINTERRUPTED THROUGH FRIDAY.

BY LATE FRIDAY...MODELS SHOW A COLD FRONT APPROACHING FROM THE
NORTHWEST WILL REACH KAUAI. THE ASSOCIATED COL IN LOW LEVEL FLOW
WILL BE NORTH OF THE ISLANDS...SO WINDS ACROSS LOCAL WATERS WILL
REMAIN TRADES AS THE FRONT APPROACHES INSTEAD OF VEERING TO
SOUTHERLIES. LATEST MODEL RUNS SHOW THIS FRONT WILL REACH THE BIG
ISLAND BY LATE SATURDAY AND THE FOLLOWING HIGH WILL USHER IN STRONG
AND GUSTY NORTH NORTHEAST WINDS IN ITS WAKE. IT IS TOO EARLY TO TELL
HOW MUCH RAINFALL THERE WILL BE AS THE FRONT PASSES BY.

&&

.AVIATION...
EXPECT PREDOMINANTLY VFR CONDITIONS AT THE TERMINALS OVERNIGHT.
HOWEVER...AIRMET SIERRA FOR MVFR CEILINGS OVER WINDWARD AND MOUNTAIN
AREAS WILL LIKELY REMAIN IN EFFECT THROUGH THE NIGHT.

&&

.MARINE...
THE CURRENT NW SWELL OVER LOCAL WATERS WILL CONTINUE TO GRADUALLY
DECLINE THROUGH MONDAY.

A MODERATE NW SWELL WILL BUILD ON TUESDAY...PEAK ON WEDNESDAY...THEN
LOWER SLOWLY ON THURSDAY. A SLIGHTLY LARGER NW SWELL IS EXPECTED TO
BUILD THURSDAY NIGHT...WITH SURF EXPECTED TO REACH ADVISORY LEVELS
BY FRIDAY ON SOME OF THE N AND W FACING SHORES.

TRADE WINDS MAY REACH SMALL CRAFT ADVISORY STRENGTH...AT LEAST
ACROSS THE TYPICALLY WINDY ZONES...BY MIDWEEK. WINDS WILL STRENGTHEN
FURTHER THIS WEEKEND DUE TO A STRONG HIGH NW OF THE STATE BEHIND A
PASSING FRONT. BY THEN...SMALL CRAFT ADVISORY CONDITIONS WILL LIKELY
EXIST IN ALL COASTAL WATERS...WITH THE POSSIBILITY OF GALE WARNINGS
IN THE CHANNELS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION/MARINE...POWELL
AVIATION...BEDAL

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

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