High Surf in Hawaii, April 3 to 5, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI APR 3 2015

.SYNOPSIS...
TRADE WIND SPEEDS WILL EASE SLIGHTLY TODAY...ESPECIALLY ACROSS THE
SMALLER ISLANDS...AS A SURFACE TROUGH MOVES TO A POSITION NORTH OF
KAUAI. AN INCREASE IN SHOWERS IS EXPECTED THROUGH SATURDAY...
ESPECIALLY OVER THE WINDWARD BIG ISLAND...DUE TO AN AREA OF ENHANCED
TROPICAL MOISTURE SPREADING UP FROM THE SOUTHEAST OVER THE EASTERN
END OF THE MAIN HAWAIIAN ISLAND CHAIN. BREEZY TRADE WIND WEATHER IS
FORECAST TO RETURN LATER THIS WEEKEND AS A SURFACE HIGH STRENGTHENS
TO THE NORTHEAST OF THE ISLANDS. EXPECT A SOMEWHAT TYPICAL
SPRINGTIME TRADE WIND WEATHER PATTERN EARLY NEXT WEEK.

&&

.DISCUSSION...
THE PRESSURE GRADIENT SOUTHWEST OF A NEARLY STATIONARY 1033 MB
SURFACE HIGH CENTERED NEAR 37N 142W...OR MORE THAN 1400 MILES
NORTHEAST OF HONOLULU...IS MAINTAINING LOCALLY BREEZY TRADE WINDS
ACROSS THE EASTERN PORTION OF THE MAIN HAWAIIAN ISLAND CHAIN EARLY
THIS MORNING. HOWEVER...A SURFACE FRONT LOCATED ABOUT 500 MILES
NORTHWEST OF LIHUE IS MOVING SLOWLY TOWARD THE NORTHEAST. THE LOWER
PRESSURE ASSOCIATED WITH THIS FEATURE IS CAUSING THE WINDS OVER MOST
OF THE WESTERN AND CENTRAL SECTIONS OF THE ISLAND CHAIN TO GRADUALLY
WEAKEN AND SHIFT TO AN EAST SOUTHEAST DIRECTION.

ALOFT...A MID-TROPOSPHERIC TROUGH IS EVIDENT NORTHWEST OF KAUAI.
THIS FEATURE HAS CAUSED A SLIGHT DESTABILIZATION OF THE ATMOSPHERE
NEAR KAUAI. HOWEVER...MOISTURE PROFILES FROM THE EARLY MORNING LIHUE
SOUNDING AND THE LATEST SATELLITE DERIVED ESTIMATES OF PRECIPITABLE
WATER /PW/ SHOWED VALUES OF ONLY ABOUT ONE INCH IN THE VICINITY OF
THE SMALLER ISLANDS. THERE WERE SCATTERED TO LOCALLY BROKEN LOW
CLOUDS AND ISOLATED SHOWERS MAINLY OCCURING OVER SOME WINDWARD AND
MAUKA SECTIONS OF THE SMALLER ISLANDS...WHILE BROKEN TO OVERCAST LOW
CLOUDS AND SCATTERED SHOWERS WERE NEAR THE WINDWARD BIG ISLAND.

THE HILO SOUNDING SHOWED SLIGHTLY HIGHER MOISTURE VALUES...WITH A PW
OF ABOUT 1.2 INCHES. HOWEVER...AN AREA OF ENHANCED TROPICAL MOISTURE
IS CURRENTLY EVIDENT ABOUT JUST SOUTH OF THE BIG ISLAND. THE
FORECAST MODELS INDICATE THIS AREA WILL CONTINUE TO SPREAD UP FROM
THE SOUTHEAST OVER THE EASTERN END OF THE MAIN HAWAIIAN ISLAND CHAIN
TODAY AND TONIGHT. SOME OF THIS ENHANCED MOISTURE MAY ALSO SPREAD UP
OVER THE SMALLER ISLANDS FROM LATER TODAY AND TONIGHT INTO THE
WEEKEND.

OUTPUT FROM THE FORECAST MODELS INDICATE THE FRONT NORTHWEST OF
KAUAI WILL WEAKEN TO A SURFACE TROUGH LATER TODAY OR TONIGHT WHEN IT
MOVES TO A POSITION NORTH OF KAUAI. ALSO...THE MID-LEVEL TROUGH WILL
CONTINUE TO SHIFT EASTWARD. THE PRESENCE OF THESE FEATURES WILL
CONTINUE TO SLACKEN THE PRESSURE GRADIENT ACROSS THE AREA...LEADING
TO WEAKER EAST TO EAST SOUTHEAST FLOW OVER MOST OF THE SMALLER
ISLANDS TODAY. PARTS OF THE BIG ISLAND MAY CONTINUE TO SEE LOCALLY
BREEZY TRADES TODAY...WITH A SLIGHT DECREASE IN WIND SPEEDS TONIGHT.

THE INCREASED MOISTURE COMBINED WITH A SLIGHT DESTABILIZATION OF THE
ATMOSPHERE DUE TO THE MID-LEVEL TROUGH WILL LIKELY LEAD TO INCREASED
SHOWERS ESPECIALLY OVER THE WINDWARD BIG ISLAND FROM TODAY INTO THIS
WEEKEND. THE MODELS ALSO INDICATE THERE MAY BE A MODEST INCREASE IN
SHOWERS OVER PORTIONS OF THE SMALLER HAWAIIAN ISLANDS AT THE SAME
TIME. THERE IS ALSO THE POTENTIAL FOR SNOW SHOWERS OVER THE BIG
ISLAND SUMMITS TONIGHT AND EARLY SATURDAY MORNING...DUE TO DEEPER
MOISTURE AND THE COLDER TEMPERATURES ALOFT ASSOCIATED WITH THE
MID-LEVEL TROUGH.

DURING THIS WEEKEND...THE SURFACE TROUGH...AS WELL AS THE ASSOCIATED
MID-LEVEL TROUGH ARE EXPECTED TO LIFT NORTH NORTHEASTWARD AWAY FROM
THE ISLANDS. THIS SHOULD ALLOW THE PRESSURE GRADIENT TO BECOME
REESTABLISHED OVER THE AREA DUE TO THE SURFACE HIGH FAR NORTHEAST OF
THE STATE BECOMING THE DOMINATE SYNOPTIC FEATURE ONCE AGAIN. THIS
WILL LEAD TO AN INCREASE OF TRADE WINDS OVER THE ISLANDS FROM THIS
WEEKEND INTO EARLY NEXT WEEK. THE GLOBAL FORECAST MODELS ALSO
CONTINUE TO INDICATE A SLIGHTLY DRIER AIR MASS MAY SPREAD ACROSS THE
AREA BY EARLY NEXT WEEK. THEREFORE...EXPECT A SOMEWHAT TYPICAL
SPRINGTIME TRADE WIND WEATHER PATTERN ACROSS MOST OF THE ISLAND
CHAIN EARLY NEXT WEEK.

&&

.AVIATION...
LIGHT TO MODERATE TRADE WIND FLOW WILL CONTINUE TO FOCUS CLOUDS AND
SHRA OVER MTN AND N THRU E SECTIONS OF THE ISLANDS TODAY AND
TONIGHT. COULD SEE BRIEF MVFR CIGS AT PHTO AND PHLI THROUGH MID
MORNING...AND AT PHNY THIS AFTERNOON...BUT PREDOMINANTLY VFR
CONDITIONS ARE EXPECTED AT ALL TERMINALS THROUGH 04/12Z.

NO AIRMETS ARE CURRENTLY IN EFFECT...AND NONE ARE ANTICIPATED
THROUGH EARLY THIS AFTERNOON.

&&

.MARINE...
LOCALLY BREEZY TRADES AND ELEVATED SEAS ARE EXPECTED TO CONTINUE
SMALL CRAFT ADVISORY /SCA/ CONDITIONS OVER THE TYPICALLY WINDY
WATERS ADJACENT TO THE BIG ISLAND TODAY. THE TRADE WINDS MAY BRIEFLY
DROP BELOW THE SCA CRITERIA TONIGHT. HOWEVER...TRADE WIND SPEEDS ARE
FORECAST TO RESTRENGTHEN TO SCA CONDITIONS OVER THE TYPICALLY WINDY
WATERS ADJACENT TO THE BIG ISLAND AND THE ISLANDS OF MAUI COUNTY
FROM SATURDAY THROUGH EARLY NEXT WEEK.

A MODEST EAST SWELL COMBINED WITH A SLIGHT INCREASE IN LOCALLY
GENERATED TRADE WIND WAVES IS EXPECTED TO BOOST SURF HEIGHTS ALONG
EAST FACING SHORES STARTING TONIGHT. AS A RESULT...SURF MAY APPROACH
THE HIGH SURF ADVISORY THRESHOLD ALONG EAST FACING SHORES FROM LATE
TONIGHT THROUGH THIS WEEKEND. ALSO...A SERIES OF SMALL NORTHWEST AND
SOUTH SWELLS WILL CONTINUE...BUT SURF IS EXPECTED TO REMAIN BELOW
THE HIGH SURF ADVISORY CRITERIA ALONG SOUTH...WEST AND NORTH FACING
SHORES OF THE ISLANDS THROUGH EARLY NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 600 PM HST THIS EVENING FOR THE WATERS
SOUTH OF THE BIG ISLAND AND THE ALENUIHAHA CHANNEL.

&&

DISCUSSION/MARINE...HOUSTON
AVIATION...JELSEMA