High Surf in Hawaii, May 7 to 9, 2016

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
341 AM HST SAT MAY 7 2016

.SYNOPSIS...
A WEAKENING FRONT WILL PUSH SOUTHWARD THROUGH THE ISLANDS
TODAY AND TONIGHT...THEN STALL OUT OVER THE EASTERN END OF THE
STATE SUNDAY THROUGH EARLY NEXT WEEK. A SHORT PERIOD OF UNSETTLED
WEATHER IS EXPECTED AS THE FRONT PUSHES THROUGH THE SMALLER
ISLANDS. THE UNSETTLED WEATHER WILL LIKELY BE MORE PERSISTENT
ACROSS WINDWARD SECTIONS OF MAUI AND THE BIG ISLAND AS THE FRONT
HANGS UP HERE THROUGH EARLY NEXT WEEK BEFORE DISSIPATING. A LIGHT
TO MODERATE TRADE WIND PATTERN IS THEN EXPECTED TO RETURN FOR THE
MIDDLE AND LATTER PART OF NEXT WEEK.

&&

.DISCUSSION...
CURRENTLY AT THE SURFACE...A WEAKENING COLD FRONT IS PUSHING
THROUGH MOLOKAI...WITH INCREASED NORTHERLY FLOW NOW IN PLACE
ACROSS KAUAI AND OAHU IN THE WAKE OF THE FRONT. INFRARED
SATELLITE IMAGERY SHOWS MOSTLY CLOUDY TO CLOUDY SKIES IN PLACE
ACROSS THE WESTERN HALF OF THE STATE...WITH LESS CLOUD COVER OVER
MAUI AND THE BIG ISLAND. MEANWHILE...RADAR IMAGERY SHOWS SCATTERED
TO NUMEROUS SHOWERS ALONG AND AHEAD OF THE FRONT...WITH SOME MORE
PERSISTENT RAINS ACROSS WINDWARD/MAUKA AREAS OF KAUAI AND OAHU
BEHIND THE FRONT. MAIN SHORT TERM CONCERN FOR TODAY REVOLVES
AROUND RAIN CHANCES.

TODAY...
THE SOUTHEASTWARD PROGRESS OF THE FRONT WILL SLOW
CONSIDERABLY...RESULTING IN AN UNSETTLED DAY ACROSS THE MAUI
COUNTY ISLANDS. OVER KAUAI AND OAHU...A DRIER AIRMASS WILL SETTLE
IN...BUT LIGHT SHOWERS ARE EXPECTED TO CONTINUE TO AFFECT
WINDWARD AND MAUKA AREAS...ESPECIALLY THIS MORNING. ACROSS THE
BIG ISLAND...LIGHT WINDS AND INCREASING MOISTURE IN ADVANCE OF THE
WEAKENING FRONT WILL LIKELY LEAD TO SOME ENHANCED SEA BREEZE
SHOWERS ALONG THE MOUNTAIN SLOPES THIS AFTERNOON.

TONIGHT THROUGH TUESDAY NIGHT...
THE 00Z GFS AND 00Z ECMWF HAVE SOME SMALL YET SIGNIFICANT
DIFFERENCES WITH RESPECT TO SYNOPTIC WEATHER DETAILS. THE GFS
SHOWS THE FRONT SHIFTING SOUTHWARD INTO EAST MAUI AND THE BIG
ISLAND SATURDAY NIGHT...WITH THE REMNANT MOISTURE LINGERING IN
THIS SAME AREA THROUGH THE FIRST HALF OF NEXT WEEK. THE ECMWF ON
THE OTHER HAND KEEPS THE FRONT AND ASSOCIATED MOISTURE OVER MAUI
COUNTY THROUGH THE PERIOD. ALTHOUGH THERE IS NOT MUCH OF A
DIFFERENCE IN OVERALL POSITIONING DETAILS...THE RESULTING WEATHER
WILL BE HIGHLY DEPENDENT ON WHERE THE FRONT AND AREA OF ENHANCED
MOISTURE HANGS UP.

OVERALL...WE WILL FOLLOW A BLENDED SOLUTION WITH A SIZABLE AMOUNT
OF WEIGHT GIVEN TO THE PREVIOUS FORECAST TO HELP MAINTAIN SOME
PERSISTENCE. THIS RESULTS IN UNSETTLED WEATHER CONDITIONS ACROSS
PRIMARILY MAUI AND THE BIG ISLAND THROUGH THE PERIOD...WITH MORE
TYPICAL TRADE WIND SHOWERS OVER WINDWARD AND MAUKA AREAS OF THE
OTHER SMALLER ISLANDS.

WEDNESDAY THROUGH NEXT FRIDAY...
MODEL DIFFERENCES CONTINUE IN THE EXTENDED PORTION OF THE
FORECAST...WITH THE ECMWF SHOWING HIGH PRESSURE BUILDING NORTH OF
THE ISLANDS RESULTING IN A TYPICAL TRADE WIND PATTERN. THE GFS ON
THE OTHER HAND SHOWS SURFACE TROUGHING DEVELOPING OVER THE
STATE...RESULTING IN A SEA AND LAND BREEZE WEATHER PATTERN. FOR
NOW WILL STICK WITH PERSISTENCE...WHICH IS IN LINE WITH TYPICAL
CLIMATOLOGY FOR THIS TIME OF YEAR. THIS RESULTS IN A LIGHT TO
MODERATE TRADE WIND PATTERN...WITH SHOWERS FOCUSED PRIMARILY
ACROSS WINDWARD AND MAUKA LOCALES.

&&

.AVIATION...
THE DIFFUSE LEADING EDGE OF A FRONT HAS REACHED MAUI COUNTY EARLY
THIS MORNING. A NARROW BAND OF LOW CLOUDS WITH EMBEDDED SHOWERS...
SOME WITH LOCALLY HEAVY RAINFALL...IS ALONG THE FRONT. CLOUD TOPS
OF UP TO AROUND 16 THOUSAND FEET IN THE VICINITY OF THE FRONT ARE
EXPECTED TO PRODUCE PERIODS OF MVFR TO ISOLATED IFR CONDITIONS AS
THE FRONT CONTINUES TO PUSH EASTWARD OVER THE CENTRAL ISLANDS THIS
MORNING. AIRMET SIERRA REMAINS IN EFFECT FOR MTN OBSC ON THE
ISLANDS OF KAUAI...OAHU AND MOLOKAI. CONDITIONS MAY IMPROVE OVER
THE HIGHER TERRAIN ON SOME OF THE ISLANDS LATER THIS MORNING OR
THIS AFTERNOON. HOWEVER...THE STRENGTHENING NORTH TO NORTHEAST
WINDS BEHIND THE FRONT WILL LIKELY CONTINUE TO KEEP LOW CLOUDS AND
SHOWERS IN PLACE ALONG MANY WINDWARD FACING SLOPES AND OVER MOST
MOUNTAIN AREAS. AIRMET SIERRA FOR MTN OBSC WILL ALSO LIKELY BE
REQUIRED FOR MAUI...AND POSSIBLY LANAI...LATER THIS MORNING.

THE FRONT IS EXPECTED TO WEAKEN AND SLOW ITS FORWARD PROGRESS
LATER TODAY OVER MAUI COUNTY. AHEAD OF THE FRONT...TERMINAL
FORECASTS SHOW MAINLY VFR CONDITIONS WILL LIKELY PREVAIL THIS
MORNING OVER THE BIG ISLAND. HOWEVER...LOCAL SEA BREEZES MAY
PRODUCE ISOLATED MVFR CONDITIONS OVER SOME PARTS OF THE BIG
ISLAND BY THIS AFTERNOON.

INCREASING NORTHEASTERLY WINDS AND LOWERING OF THE INVERSION BEHIND
THE FRONT MAY RESULT IN MODERATE LOW-LEVEL TURBULENCE OVER LEEWARD
AREAS OF SOME OF THE WESTERN ISLANDS LATER TODAY OR TONIGHT. WE
WILL MONITOR OBSERVATIONS IN CASE AIRMET TANGO IS NEEDED FOR THESE
CONDITIONS.

&&

.MARINE...
LATEST BUOY OBSERVATIONS INDICATE THAT A LONG PERIOD S SWELL IS
RUNNING SLIGHTLY ABOVE WAVE WATCH GUIDANCE. THIS IS EXPECTED TO
RESULT IN ADVISORY LEVEL SURF ALONG S FACING SHORES TODAY AND
TONIGHT...SO A HIGH SURF ADVISORY HAS BEEN ISSUED THROUGH 6 AM
SUNDAY. THIS SWELL WILL THEN SLOWLY SUBSIDE THROUGH EARLY NEXT
WEEK. A RELATIVELY SHORT-PERIOD NNW SWELL IS EXPECTED TO BUILD
TODAY. THIS SWELL WILL PERSIST INTO NEXT WEEK AS THE DIRECTION
SHIFTS TO THE N...DUE TO A PERSISTENT BUT RELATIVELY WEAK SURFACE
LOW TO THE DISTANT NNE. PEAK SURF HEIGHTS ALONG N FACING SHORES
ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS. THE OAHU SURF
DISCUSSION /SRDHFO/ WAS UPDATED THIS AFTERNOON...AND CONTAINS
ADDITIONAL INFORMATION ON THE SOURCE OF THE SWELLS.

HIGH PRESSURE BUILDING WELL NW OF THE ISLANDS WILL PUSH A FRONT
DOWN THE ISLAND CHAIN...BRINGING INCREASING NNE WINDS IN ITS WAKE.
A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT FOR THE KAUAI
LEEWARD WATERS THROUGH 6 PM THIS EVENING. WINDS MAY ALSO
STRENGTHEN ENOUGH TO SUPPORT THE ISSUANCE OF AN SCA IN THE
TYPICALLY WINDIER WATERS AROUND MAUI AND THE BIG ISLAND ON SUNDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST SUNDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU SOUTH SHORE-WAIANAE COAST-MOLOKAI-
LANAI MAKAI-KAHOOLAWE-MAUI LEEWARD WEST-WINDWARD HALEAKALA-
LEEWARD HALEAKALA-KONA-SOUTH BIG ISLAND-BIG ISLAND NORTH AND
EAST.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR KAUAI
LEEWARD WATERS.

&&

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